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  • 1.
    A Asif, Farazee M
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Machine and Process Technology.
    Circular Manufacturing Systems: A development framework with analysis methods and tools for implementation2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The society today lives on the philosophy of ‘take-make-use-dispose.’ In the long run, this is not sustainable as the natural resources and the waste carrying capacity of the earth are limited. Therefore, it is essential to reduce dependency on the natural resources by decoupling the growth from the consumption. In this venture, both the society and the manufacturing industry have a vital role to play. The society needs to shift towards Circular Economy that rests upon the philosophy of ‘take-make-use-reuse’ and the manufacturing industry has to be a major stakeholder in this shift. Despite being proven to be both economically and environmentally beneficial, successful examples of circular systems are few today. This is primarily due to two reasons; firstly, there is a lack of systemic and systematic approach to guide industries and secondly, there is a lack of analysis methods and tools that are capable of assessing different aspects of circular manufacturing systems. Taking on to these challenges, the objective of this research is to bring forward a framework with methods and decision support tools that are essential to implement circular manufacturing systems. The initial conceptual framework with the systemic approach is developed based on extensive review and analysis of research, which is further adapted for industrial implementation. Systematic analysis methods, decision support and implementation tools are developed to facilitate this adaptation. This development has been supported by four cases from diverse manufacturing sectors. Behind each decision support tool, there are analysis methods built upon mainly system dynamics principles. These tools are based on simulation platforms called Stella and Anylogic. Among other things, these tools are capable of assessing the performance of closed-loop supply chains, consequences of resource scarcity, potential gains from resource conservation and overall economic and environmental performance of circular manufacturing systems.

  • 2.
    A Asif, Farazee M
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Machine and Process Technology.
    Rashid, Amir
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Machine and Process Technology.
    Bianchi, Carmine
    University of Palermo (ITALY) Faculty of Political Sciences - Department of International Studies .
    Nicolescu, Mihai
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Machine and Process Technology.
    Performance analysis of the closed loop supply chain2012In: Journal of Remanufacturing, ISSN 2210-4690, Vol. 2, no 4Article in journal (Refereed)
    Abstract [en]

    Purpose

    The question of resource scarcity and emerging pressure of environmental legislations has brought a new challenge for the manufacturing industry. On the one hand, there is a huge population that demands a large quantity of commodities; on the other hand, these demands have to be met by minimum resources and pollution. Resource conservative manufacturing (ResCoM) is a proposed holistic concept to manage these challenges. The successful implementation of this concept requires cross functional collaboration among relevant fields, and among them, closed loop supply chain is an essential domain. The paper aims to highlight some misconceptions concerning the closed loop supply chain, to discuss different challenges, and in addition, to show how the proposed concept deals with those challenges through analysis of key performance indicators (KPI).

    Methods

    The work presented in this paper is mainly based on the literature review. The analysis of performance of the closed loop supply chain is done using system dynamics, and the Stella software has been used to do the simulation. Findings The results of the simulation depict that in ResCoM; the performance of the closed loop supply chain is much enhanced in terms of supply, demand, and other uncertainties involved. The results may particularly be interesting for industries involved in remanufacturing, researchers in the field of closed loop supply chain, and other relevant areas. Originality The paper presented a novel research concept called ResCoM which is supported by system dynamics models of the closed loop supply chain to demonstrate the behavior of KPI in the closed loop supply chain.

  • 3.
    A Elhassan, Amro
    KTH, School of Electrical Engineering (EES).
    Building automation and control2012Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 4.
    A, Fredrik
    et al.
    KTH, School of Electrical Engineering (EES).
    Forsberg, A
    KTH, School of Electrical Engineering (EES).
    Forsén, Tobias
    KTH, School of Electrical Engineering (EES).
    Tracking Using Wireless Camera Networks2015Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 5. A. Hosseini, V.
    et al.
    Karlsson, L.
    Örnek, Cem
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Chemistry, Surface and Corrosion Science. Swerea KIMAB AB.
    Reccagni, P.
    Wessman, S.
    Engelberg, D.
    Microstructure and functionality of a uniquely graded super duplex stainless steel designed by a novel arc heat treatment method2018In: Materials Characterization, ISSN 1044-5803, E-ISSN 1873-4189, Vol. 139, p. 390-400Article in journal (Refereed)
    Abstract [en]

    A novel arc heat treatment technique was applied to design a uniquely graded super duplex stainless steel (SDSS), by subjecting a single sample to a steady state temperature gradient for 10 h. A new experimental approach was used to map precipitation in microstructure, covering aging temperatures of up to 1430 °C. The microstructure was characterized and functionality was evaluated via hardness mapping. Nitrogen depletion adjacent to the fusion boundary depressed the upper temperature limit for austenite formation and influenced the phase balance above 980 °C. Austenite/ferrite boundaries deviating from Kurdjumov–Sachs orientation relationship (OR) were preferred locations for precipitation of σ at 630–1000 °C, χ at 560–1000 °C, Cr2N at 600–900 °C and R between 550 °C and 700 °C. Precipitate morphology changed with decreasing temperature; from blocky to coral-shaped for σ, from discrete blocky to elongated particles for χ, and from polygonal to disc-shaped for R. Thermodynamic calculations of phase equilibria largely agreed with observations above 750 °C when considering nitrogen loss. Formation of intermetallic phases and 475 °C-embrittlement resulted in increased hardness. A schematic diagram, correlating information about phase contents, morphologies and hardness, as a function of exposure temperature, is introduced for evaluation of functionality of microstructures.

  • 6.
    A. M. Naiini, Maziar
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Horizontal Slot Waveguides for Silicon Photonics Back-End Integration2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents the development of integrated silicon photonic devices. These devices are compatible with the present and near future CMOS technology. High-khorizontal grating couplers and waveguides are proposed. This work consists of simulations and device design, as well as the layout for the fabrication process, device fabrication, process development, characterization instrument development and electro-optical characterizations.

    The work demonstrates an alternative solution to costly silicon-on-insulator photonics. The proposed solution uses bulk silicon wafers and thin film deposited waveguides. Back-end deposited horizontal slot grating couplers and waveguides are realized by multi-layers of amorphous silicon and high-k materials.

    The achievements of this work include: A theoretical study of fully etched slot grating couplers with Al2O3, HfO2 and AIN, an optical study of the high-k films with spectroscopic ellipsometry, an experimental demonstration of fully etched SiO2 single slot grating couplers and double slot Al2O3 grating couplers, a practical demonstration of horizontal double slot high-k waveguides, partially etched Al2O3 single slot grating couplers, a study of a scheme for integration of the double slot Al2O3  waveguides with selectively grown germanium PIN photodetectors, realization of test chips for the integrated germanium photodetectors, and study of integration with graphene photodetectors through embedding the graphene into a high-k slot layer.

    From an application point of view, these high-k slot waveguides add more functionality to the current silicon photonics. The presented devices can be used for low cost photonics applications. Also alternative optical materials can be used in the context of this photonics platform.

    With the robust design, the grating couplers result in improved yield and a more cost effective solution is realized for integration of the waveguides with the germanium and graphene photodetectors.

     

     

     

     

  • 7.
    A Monfared, Behzad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Design and Construction of a Small Ammonia Heat Pump2010Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In view of the fact that most of the synthetic refrigerants, in case of leakage or release, are harmful to the environment by contributing in global warming or depleting stratospheric ozone layer, many research works have been done recently to find alternative refrigerants posing no or negligible threat to the environment. Among alternative refrigerants, ammonia, a natural refrigerant with zero Global Warming Potential (GWP) and Ozone Depletion Potential (ODP), can be a sensible choice.Although ammonia has been used for many years in large industrial systems, its application in small units is rare. In this project a small heat pump with about 7 kW heating capacity at -5 °C and +40 °C evaporation and condensation temperatures is designed and built to work with ammonia as refrigerant. The heat pump is expected to produce enough heat to keep a single-family house warm in Sweden and to provide tap hot water for the house. After successful completion of this project, it is planned to install the heat pump in a house to test it throughout a heating season to study its performance in real working conditions.Since ammonia is flammable and toxic in high concentrations, the refrigerant charge is tried to be kept low in the heat pump to reduce the risk of fire or poisoning in case of unwanted release of refrigerant to the surroundings. The compact design of the heat pump helps reducing the refrigerant charge. Besides, considering the limited space normally reserved for installation of a heat pump in a house, the compact design of the heat pump is necessary.

  • 8.
    A Monfared, Behzad
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Magnetic Refrigeration for Near Room-Temperature Applications2018Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Refrigeration plays a crucial role in many different sectors and consumes about 17% of the electricity produced globally. This significant energy consumption implies large share of refrigeration in primary energy consumption and other environmental impacts. In addition to the environmental impacts associated with energy consumption, the vapor-compression systems contribute in global warming due to the release of their gaseous refrigerants into the atmosphere. As an alternative technology for near room-temperature applications, magnetic refrigeration is proposed by some researchers to eliminate the release of gaseous refrigerants into the atmosphere and to reduce the energy consumption. This thesis is a compilation of a number of studies done on magnetic refrigeration for room-temperature applications.

    In the first study, the environmental impacts associated to magnetic refrigeration are looked at closely through a life cycle assessment. The life cycle assessment indicates that because of the environmental burdens related to the rare-earth materials used in magnetic refrigeration, the reduction in the environmental impacts is not guaranteed by switching to magnetic refrigeration technology. Accordingly to avoid the extra environmental impacts the magnetic refrigeration systems should use magnetic materials frugally, which requires an optimized design. In addition, operation with higher efficiency compared to vapor-compression systems is necessary to have environmental advantages, at least in some impact categories.

    A practical method to optimize the design of magnetic refrigeration systems, e.g. to have a compact design or high efficiency, is utilizing a flexible software model, with which the effect of varying different parameters on the performance of the system can be simulated. Such a software model of the magnetic refrigeration system is developed and validated in this project. In developing the model one goal is to add to the precision of the simulated results by taking more details into consideration. This goal is achieved by an innovative way of modeling the parasitic heat transfer and including the effect of the presence of magnetocaloric materials on the strength of the field created by the magnet assembly. In addition, some efforts are made to modify or correct the existing correlations to include the effect of binding agents used in some active magnetic regenerators. Validation of the developed software model is done using the experimental results obtained from the prototype existing at the Department of Energy Technology, KTH Royal Institute of Technology.

    One of the parameters that can be modified by the developed software model is the choice of the magnetocaloric materials for each layer in a layered active magnetic regenerator. Utilizing the software model for optimizing the choice of the materials for the layers reveals that materials with critical temperatures equal to the cyclic average temperature of the layers in which they are used do not necessarily result in the desired optimum performance. In addition, for maximizing different outputs of the models, such as energy efficiency or temperature lift sustained at the two ends of the regenerators, different choice of materials for the layers are needed. Therefore, in other studies seeking to improve one of the outputs of a system, the choice of the transition or critical temperatures of the materials for each layer is an additional parameter to be optimized.

    The prototype existing at the Department of Energy Technology, KTH Royal Institute of Technology, was initially designed for replacing the vapor-compression system of a professional refrigerator. However, it could not fulfil the requirements for which it was initially designed. The aforementioned developed simulation model is used to see how much the choice of the materials, size of the particles, and number of layers can enhance the performance while the operation frequency and flow rate of the heat transfer fluid are at their optimum values. In other words, in that study the room for improvement in the performance without applying major changes in the system such as the geometry of the regenerator, which implies redesigning the whole magnet assembly, is investigated. In the redesign process the effect of binding agent and the limitations associated to different properties of it is also investigated theoretically. Nevertheless, the study did not show that with keeping the geometry of the regenerators and the currently existing magnetocaloric materials the initial goals of the prototype can be achieved.

    In the next study more flexible choice of geometries and magnetocaloric materials are considered. In fact, in this study it is investigated how much the magnetocaloric materials need to be improved so that magnetic refrigeration systems can compete with vapor-compression ones in terms of performance. For the two investigated cases, the magnetic-field dependent properties of the currently existing materials are enough provided that some other issues such as low mechanical stability and inhomogeneity of the properties are solved. Nevertheless, for more demanding design criteria, such as delivering large cooling capacity over a considerable temperature span while the magnetic materials are used sparingly, the magnetic-field dependent properties need to be enhanced, as well.

    A less explored area in room-temperature magnetic refrigeration is the subject of another study included in the thesis. In this study, solid-state magnetic refrigeration systems with Peltier elements as heat switches are modeled. Since the Peltier elements consume electricity to pump heat, the modeled systems can be considered hybrid magnetocaloric-Peltier cooling systems. For such systems the detailed transient behavior of the Peltier elements together with layers of magnetocaloric materials are modeled. The mathematical model is suitable for implementation in programing languages without the need for commercial modeling platforms. The parameters affecting the performance of the modeled system are numerous, and optimization of them requires a separate study. However, the preliminary attempts on optimizing the modeled system does not give promising results. Accordingly, focusing on passive heat switches can be more beneficial.

  • 9.
    A Monfared, Behzad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Applied Thermodynamics and Refrigeration.
    Palm, Björn
    KTH, School of Industrial Engineering and Management (ITM), Energy Technology.
    Material requirements for magnetic refrigeration applications2018In: International journal of refrigeration, ISSN 0140-7007, E-ISSN 1879-2081, Vol. 96, p. 25-37Article in journal (Refereed)
    Abstract [en]

    A primary motivation underlying the research on room-temperature magnetic refrigeration is reaching energy efficiency levels beyond what is achievable with vapor-compression technology. However, the goal of building commercially viable magnetic refrigeration systems with high performance and competitive price has not been achieved yet. One of the obstacles to reach this goal is the inadequate properties of the currently existing magnetocaloric materials. In this article, the needed improvements in the properties of the magnetocaloric materials are investigated. Two existing vapor-compression refrigerators are used as reference for the required performance, and magnetic refrigerators are simulated using a numerical model. Apart from the requirements such as uniformity of transition temperature for each layer, small increment in transition temperature in adjacent layers, and mechanical strength of the materials, the study shows that for the investigated cases materials with adiabatic entropy change 2.35 times larger than the existing materials are needed to outperform vapor-compression systems.

  • 10.
    A. Taher, Ali
    KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Building Technology.
    BIM Software Capability and Interoperability Analysis: An analytical approach toward structural usage of BIM software (S-BIM)2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This study focused on the structuralanalysis of BIM models. Different commercial software (Autodesk products and Rhinoceros)are presented through modelling and analysis of different structures with varying complexity,section properties, geometry, and material. Beside the commercial software, differentarchitectural and different tools for structural analysis are evaluated (dynamo, grasshopper,add-on tool, direct link, indirect link via IFC).

  • 11.
    A Österman, Sami
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Kumar, Shirish
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Vattenskärning: Teknologin och dess tillämpningsområden2010Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Water jet cutting is generally considered to be a versatile processing technique with a variety of applications. Pure water jet cutting makes it possible to cut through soft materials like rubber, while an added abrasive allows cutting of including steel and ceramics. The cut leaves neither any residual stress nor heat stress in the material. In addition, the surface finish is often of high enough quality, making post treatment unnecessary. The process does not yield in any dangerous gases and is relatively environmentally friendly. The purpose of this thesis was to investigate the water jet technology, its current, as well as new application areas. The goal was also to compare the technique with alternative processing methods in order to clarify the advantages and disadvantages between them. This was done in order to investigate which technologies are most appropriate to use depending on properties such as material, material thickness and size of the produced series. This paper has been written together from Sweden and France and a choice was hence made to investigate if the uses of water jet cutting differ between the two countries. To meet the objective, three questions were used to investigate how to expand the application areas of water jet cutting, what advantages and disadvantages there are between water jet cutting and other processing methods and how the scope of its applications differs between France and Sweden. The main sources of information for the work have been interviews with manufacturing companies that use water jet cutting, suppliers of water jet cutting machines and research institutes. Research articles have been used in order to extend the range of gathered information. Among primary sources for this report were websites of companies in the processing industry. This thesis shows that water jet technology is applicable in many industries and application areas that differ between France and Sweden, in France, used water jets are mainly used in the food industry, while it is more widespread in the engineering industry in Sweden. Companies in the Swedish market are skeptical about the use of water jet cutters exceeding 400 MPa, although it suggests many advantages. The main limitation of the water jet cutting procedure is the thickness of the material. Cutting steel beyond 30 mm in thickness, can result in a stream lag by delaying the water jet and thereby induce non‐precise cutting. This problem may be solved by changing the cutting parameters such as cutting speed or by inclining the cutting nozzle. Following an evaluation of plasma, laser and water jet cutters, none of the methods is directly competing with one another, since each single cutting technique is best suited for their intended use. The techniques complement each other rather than competing with one another.

  • 12. Aabou, M.
    et al.
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et. al.,
    ZZ -> l(+)l(-)l '(+)l '(-) cross-section measurements and search for anomalous triple gauge couplings in 13 TeV pp collisions with the ATLAS detector2018In: Physical Review C. Nuclear Physics, ISSN 0556-2813, E-ISSN 1089-490XArticle in journal (Refereed)
    Abstract [en]

    Measurements of ZZ production in the l(+)l(-)l'(+)l'(-) channel in proton-proton collisions at 13 TeV center-of-mass energy at the Large Hadron Collider are presented. The data correspond to 36.1 fb(-1) of collisions collected by the ATLAS experiment in 2015 and 2016. Here l and l ' stand for electrons or muons. Integrated and differential ZZ -> l(+)l(-)l'(+)l'(-) cross sections with Z -> l(+)l(-) candidate masses in the range of 66 GeV to 116 GeV are measured in a fiducial phase space corresponding to the detector acceptance and corrected for detector effects. The differential cross sections are presented in bins of twenty observables, including several that describe the jet activity. The integrated cross section is also extrapolated to a total phase space and to all standard model decays of Z bosons with mass between 66 GeV and 116 GeV, resulting in a value of 17.3 +/- 0.9 [+/- 0.6(start) +/- 0.5 (syst) +/- 0.6 (lumi)] pb. The measurements are found to be in good agreement with the standard model. A search for neutral triple gauge couplings is performed using the transverse momentum distribution of the leading Z boson candidate. No evidence for such couplings is found and exclusion limits are set on their parameters.

  • 13. Aaboud, B
    et al.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for heavy long-lived charged R-hadrons with the ATLAS detector in 3.2 fb(-1) of proton-proton collision data at root s=13 TeV2016In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 760, p. 647-665Article in journal (Refereed)
    Abstract [en]

    A search for heavy long-lived charged R-hadronsis reported using a data sample corresponding to 3.2fb(-1)of proton-proton collisions at root s = 13 TeV collected by the ATLAS experiment at the Large Hadron Collider at CERN. The search is based on observables related to large ionisation losses and slow propagation velocities, which are signatures of heavy charged particles travelling significantly slower than the speed of light. No significant deviations from the expected background are observed. Upper limits at 95% confidence level are provided on the production cross section of long-lived R-hadronsin the mass range from 600 GeV to 2000 GeV and gluino, bottom and top squark masses are excluded up to 1580 GeV, 805 GeV and 890 GeV, respectively.

  • 14. Aaboud, B
    et al.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for Higgs and Z Boson Decays to phi gamma with the ATLAS Detector2016In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 117, no 11, article id 111802Article in journal (Refereed)
    Abstract [en]

    A search for the decays of the Higgs and Z bosons to a phi meson and a photon is performed with a pp collision data sample corresponding to an integrated luminosity of 2.7 fb(-1) collected at root s = 13 TeV with the ATLAS detector at the LHC. No significant excess of events is observed above the background, and 95% confidence level upper limits on the branching fractions of the Higgs and Z boson decays to phi gamma of 1.4 x 10(-3) and 8.3 x 10(-6), respectively, are obtained.

  • 15. Aaboud, B
    et al.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Search for TeV-scale gravity signatures in high-mass final states with leptons and jets with the ATLAS detector at s=13 TeV2016In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 760, p. 520-537Article in journal (Refereed)
    Abstract [en]

    A search for physics beyond the Standard Model, in final states with at least one high transverse momentum charged lepton (electron or muon) and two additional high transverse momentum leptons or jets, is performed using 3.2 fb (1) of proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider in 2015 at root s = 13 TeV. The upper end of the distribution of the scalar sum of the transverse momenta of leptons and jets is sensitive to the production of high-mass objects. No excess of events beyond Standard Model predictions is observed. Exclusion limits are set for models of microscopic black holes with two to six extra dimensions.

  • 16. Aaboud, B
    et al.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    Search for scalar leptoquarks in pp collisions at √s = 13 TeV with the ATLAS experiment2016In: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 18, no 9, article id 093016Article in journal (Refereed)
    Abstract [en]

    We report a search for first generation scalar leptoquarks using 1.03 fb(-1) of proton-proton collisions data produced by the Large Hadron Collider at root s = 7 TeV and recorded by the ATLAS experiment. Leptoquarks are sought via their decay into an electron or neutrino and a quark, producing events with two oppositely charged electrons and at least two jets, or events with an electron, missing transverse momentum and at least two jets. Control data samples are used to validate background predictions from Monte Carlo simulation. In the signal region, the observed event yields are consistent with the background expectations. We exclude at 95% confidence level the production of first generation scalar leptoquark with masses m(LQ) < 660 (607) GeV when assuming the branching fraction of a leptoquark to a charged lepton is equal to 1.0 (0.5).

  • 17. Aaboud, M
    et al.
    Amorim, Antonio
    KTH.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L
    et al.,
    Search for metastable heavy charged particles with large ionization energy loss in pp collisions at root s=13 TeV using the ATLAS experiment2016In: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 93, no 11, article id 112015Article in journal (Refereed)
    Abstract [en]

    This paper presents a search for massive charged long-lived particles produced in pp collisions at root s = 13 TeV at the LHC using the ATLAS experiment. The data set used corresponds to an integrated luminosity of 3.2 fb(-1). Many extensions of the Standard Model predict the existence of massive charged long-lived particles, such as R-hadrons. These massive particles are expected to be produced with a velocity significantly below the speed of light, and therefore to have a specific ionization higher than any Standard Model particle of unit charge at high momenta. The Pixel subsystem of the ATLAS detector is used to measure the ionization energy loss of reconstructed charged particles and to search for such highly ionizing particles. The search presented here has much greater sensitivity than a similar search performed using the ATLAS detector in the root s = 8 TeV data set, thanks to the increase in expected signal cross section due to the higher center-of-mass energy of collisions, to an upgraded detector with a new silicon layer close to the interaction point, and to analysis improvements. No significant deviation from Standard Model background expectations is observed, and lifetime-dependent upper limits on R-hadron production cross sections and masses are set. Gluino R-hadrons with lifetimes above 0.4 ns and decaying to q (q) over bar plus a 100 GeV neutralino are excluded at the 95% confidence level, with lower mass limit ranging between 740 and 1590 GeV. In the case of stable R-hadrons the lower mass limit at the 95% confidence level is 1570 GeV

  • 18.
    Aaboud, M.
    et al.
    Univ Mohamed Premier, Fac Sci, Oujda, Morocco.;LPTPM, Oujda, Morocco..
    Collaboration, A. T. L. A. S.
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    CERN, Geneva, Switzerland..
    et al.,
    Measurements of Higgs boson properties in the diphoton decay channel with 36 fb(-1) of pp collision data at root s=13 TeV with the ATLAS detector2018In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 98, no 5, article id 052005Article in journal (Refereed)
    Abstract [en]

    Properties of the Higgs boson are measured in the two-photon final state using 36.1 fb(-1) of proton-proton collision data recorded at root s = 13 TeV by the ATLAS experiment at the Large Hadron Collider. Cross-section measurements for the production of a Higgs boson through gluon-gluon fusion, vector-boson fusion, and in association with a vector boson or a top-quark pair are reported. The signal strength, defined as the ratio of the observed to the expected signal yield, is measured for each of these production processes as well as inclusively. The global signal strength measurement of 0.99 +/- 0.14 improves on the precision of the ATLAS measurement at root s = 7 and 8 TeV by a factor of two. Measurements of gluon-gluon fusion and vector-boson fusion productions yield signal strengths compatible with the Standard Model prediction. Measurements of simplified template cross sections, designed to quantify the different Higgs boson production processes in specific regions of phase space, are reported. The cross section for the production of the Higgs boson decaying to two isolated photons in a fiducial region closely matching the experimental selection of the photons is measured to be 55 +/- 10 fb, which is in good agreement with the Standard Model prediction of 64 +/- 2 fb. Furthermore, cross sections in fiducial regions enriched in Higgs boson production in vector-boson fusion or in association with large missing transverse momentum, leptons or top-quark pairs are reported. Differential and double-differential measurements are performed for several variables related to the diphoton kinematics as well as the kinematics and multiplicity of the jets produced in association with a Higgs boson. These differential cross sections are sensitive to higher order QCD corrections and properties of the Higgs boson, such as its spin and CP quantum numbers. No significant deviations from a wide array of Standard Model predictions are observed. Finally, the strength and tensor structure of the Higgs boson interactions are investigated using an effective Lagrangian, which introduces additional CP-even and CP-odd interactions. No significant new physics contributions are observed.

  • 19.
    Aaboud, M.
    et al.
    Univ Mohamed Premier, Fac Sci, Oujda, Morocco.;LPTPM, Oujda, Morocco..
    Collaboration, A. T. L. A. S.
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    CERN, Geneva, Switzerland..
    et al.,
    Observation of Higgs boson production in association with a top quark pair at the LHC with the ATLAS detector2018In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 784, p. 173-191Article in journal (Refereed)
    Abstract [en]

    The observation of Higgs boson production in association with a top quark pair (t (t) over barH), based on the analysis of proton-proton collision data at a centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the Large Hadron Collider, is presented. Using data corresponding to integrated luminosities of up to 79.8 fb(-1), and considering Higgs boson decays into b (b) over bar, WW*, tau(+)tau(-), gamma gamma, and ZZ*, the observed significance is 5.8 standard deviations, compared to an expectation of 4.9 standard deviations. Combined with the t (t) over barH searches using a dataset corresponding to integrated luminosities of 4.5 fb(-1) at 7 TeV and 20.3 fb(-1) at 8 TeV, the observed (expected) significance is 6.3 (5.1) standard deviations. Assuming Standard Model branching fractions, the total t (t) over barH production cross section at 13 TeV is measured to be 670 +/- 90(stat.)(-100)(+110)(syst.) fb, in agreement with the Standard Model prediction.

  • 20. Aaboud, M D
    et al.
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Top-quark mass measurement in the all-hadronic t(t)over-bar decay channel at root s=8 TeV with the ATLAS detector2017In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 9Article in journal (Refereed)
    Abstract [en]

    The top-quark mass is measured in the all-hadronic top-antitop quark decay channel using proton-proton collisions at a centre-of-mass energy of root s = 8 TeV with the ATLAS detector at the CERN Large Hadron Collider. The data set used in the analysis corresponds to an integrated luminosity of 20.2 fb(-1). The large multi-jet background is modelled using a data-driven method. The top-quark mass is obtained from template fits to the ratio of the three-jet to the dijet mass. The three-jet mass is obtained from the three jets assigned to the top quark decay. From these three jets the dijet mass is obtained using the two jets assigned to the W boson decay. The top-quark mass is measured to be 173.72 +/- 0.55 (stat.) +/- 1.01 (syst.) GeV.

  • 21.
    Aaboud, M.
    et al.
    Univ Mohamed Premier, Fac Sci, Oujda, Morocco.;LPTPM, Oujda, Morocco..
    Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et. al,
    Combination of the Searches for Pair-Produced Vectorlike Partners of the Third-Generation Quarks at root s=13 TeV with the ATLAS Detector2018In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 121, no 21, article id 211801Article in journal (Refereed)
    Abstract [en]

    A combination of the searches for pair-produced vectorlike partners of the top and bottom quarks in various decay channels (T -> Zt/Wb/Ht, B -> Zb/Wt/Hb) is performed using 36.1 fb(-1) of pp collision data at root s = 13 TeV with the ATLAS detector at the Large Hadron Collider. The observed data are found to be in good agreement with the standard model background prediction in all individual searches. Therefore, combined 95% confidence-level upper limits are set on the production cross section for a range of vectorlike quark scenarios, significantly improving upon the reach of the individual searches. Model-independent limits are set assuming the vectorlike quarks decay to standard model particles. A singlet T is excluded for masses below 1.31 TeV and a singlet B is excluded for masses below 1.22 TeV. Assuming a weak isospin (T, B) doublet and vertical bar V-Tb vertical bar << vertical bar V-tB vertical bar, T and B masses below 1.37 TeV are excluded.

  • 22. Aaboud, M.
    et al.
    Kastanas, A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, B.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, C. C.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, G.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. E.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, J.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    ATLAS Collaboration,
    Prompt and non-prompt J/ ψ elliptic flow in Pb+Pb collisions at √sNN=5.02 Tev with the ATLAS detector2018In: The European Physical Journal CArticle in journal (Refereed)
    Abstract [en]

    The elliptic flow of prompt and non-prompt J/ ψ was measured in the dimuon decay channel in Pb+Pb collisions at sNN=5.02 TeV with an integrated luminosity of 0.42nb-1 with the ATLAS detector at the LHC. The prompt and non-prompt signals are separated using a two-dimensional simultaneous fit of the invariant mass and pseudo-proper decay time of the dimuon system from the J/ ψ decay. The measurement is performed in the kinematic range of dimuon transverse momentum and rapidity 9 < pT< 30 GeV , | y| < 2 , and 0–60% collision centrality. The elliptic flow coefficient, v2, is evaluated relative to the event plane and the results are presented as a function of transverse momentum, rapidity and centrality. It is found that prompt and non-prompt J/ ψ mesons have non-zero elliptic flow. Prompt J/ ψv2 decreases as a function of pT, while for non-prompt J/ ψ it is, with limited statistical significance, consistent with a flat behaviour over the studied kinematic region. There is no observed dependence on rapidity or centrality.

  • 23. Aaboud, M.
    et al.
    Kastanas, A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, C.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, G.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. E.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, J.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et.al.,
    Measurement of the cross section for isolated-photon plus jet production in pp collisions at root s=13 TeV using the ATLAS detector2018In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, no 780, p. 578-602Article in journal (Refereed)
    Abstract [en]

    The dynamics of isolated-photon production in association with a jet in proton-proton collisions at a centre-of-mass energy of 13 TeV are studied with theATLAS detector at the LHC using a dataset with an integrated luminosity of 3.2 fb(-1). Photons are required to have transverse energies above 125 GeV. Jets are identified using the anti-k(t) algorithm with radius parameter R = 0.4 and required to have transverse momenta above 100 GeV. Measurements of isolated-photon plus jet cross sections are presented as functions of the leading-photon transverse energy, the leading-jet transverse momentum, the azimuthal angular separation between the photon and the jet, the photon-jet invariant mass and the scattering angle in the photon-jet centre-of-mass system. Tree-level plus parton-shower predictions from SHERPA and PYTHIA as well as next-to-leading-order QCD predictions from JETPHOX and SHERPA are compared to the measurements. 

  • 24. Aaboud, M.
    et al.
    Kastanas, A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, C.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, G.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. E.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, J.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et.al.,
    Search for pair production of heavy vector-like quarks decaying into high-(PT) W bosons and top quarks in the lepton-plus-jets final state in pp collisions at root s=13 TeV with the ATLAS detector2018In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 8Article in journal (Refereed)
    Abstract [en]

    A search is presented for the pair production of heavy vector-like B quarks, primarily targeting B quark decays into a W boson and a top quark. The search is based on 36.1 fb(-1) of pp collisions at root s = 13 TeV recorded in 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. Data are analysed in the lepton-plus-jets final state, characterised by a high-transverse-momentum isolated electron or muon, large missing transverse momentum, and multiple jets, of which at least one is b-tagged. No significant deviation from the Standard Model expectation is observed. The 95% confidence level lower limit on the B mass is 1350 GeV assuming a 100% branching ratio to Wt. In the SU(2) singlet scenario, the lower mass limit is 1170 GeV. The 100% branching ratio limits are found to be also applicable to heavy vector-like X production, with charge +5/3, that decay into Wt. This search is also sensitive to a heavy vector-like B quark decaying into other final states (Zb and Hb) and thus mass limits on B production are set as a function of the decay branching ratios.

  • 25. Aaboud, M.
    et al.
    Kastanas, K. A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, B.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, C.C.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, G.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. E.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, J.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et.al.,
    Search for WW/WZ resonance production in lvqq final states in pp collisions at root s=13 TeV with the ATLAS detector2018In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479Article in journal (Refereed)
    Abstract [en]

    A search is conducted for new resonances decaying into a WW or WZ boson pair, where one W boson decays leptonically and the other W or Z boson decays hadronically. It is based on proton-proton collision data with an integrated luminosity of 36.1 fb(-1) collected with the ATLAS detector at the Large Hadron Collider at a centre-of-mass energy of root s = 13 TeV in 2015 and 2016. The search is sensitive to diboson resonance production via vector-boson fusion as well as quark-antiquark annihilation and gluon-gluon fusion mechanisms. No significant excess of events is observed with respect to the Standard Model backgrounds. Several benchmark models are used to interpret the results. Limits on the production cross section are set for a new narrow scalar resonance, a new heavy vector-boson and a spin-2 Kaluza-Klein graviton.

  • 26. Aaboud, M.
    et al.
    Kastanas, K. A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, B.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, G.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. E.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, J.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    ATLAS Collaboration,
    et.al.,
    A search for pair-produced resonances in four-jet final states at root s=13 TeV with the ATLAS detector2018In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 78, no 3Article in journal (Refereed)
    Abstract [en]

    A search for massive coloured resonances which are pair-produced and decay into two jets is presented. The analysis uses 36.7 fb(-1) of root s = 13 TeV pp collision data recorded by the ATLAS experiment at the LHC in 2015 and 2016. No significant deviation from the background prediction is observed. Results are interpreted in a SUSY simplified model where the lightest supersymmetric particle is the top squark, (t) over tilde, which decays promptly into two quarks through R-parity-violating couplings. Top squarks with masses in the range 100 GeV < m((T) over tilde) < 410 GeV are excluded at 95% confidence level. If the decay is into a b-quark and a light quark, a dedicated selection requiring two b-tags is used to exclude masses in the ranges 100 GeV < m((t) over tilde) < 470 GeV and 480 GeV < m(<(t)over tilde>) < 610 GeV. Additional limits are set on the pair-production of massive colour-octet resonances.

  • 27.
    Aaboud, M.
    et al.
    Univ Mohamed Premier, Fac Sci, Oujda, Morocco.;LPTPM, Oujda, Morocco..
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    CERN, Geneva, Switzerland..
    et al.,
    Measurements of differential cross sections of top quark pair production in association with jets in pp collisions at root s=13 TeV using the ATLAS detector2018In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 10, article id 159Article in journal (Refereed)
    Abstract [en]

    Measurements of di ff erential cross sections of top quark pair production in association with jets by the ATLAS experiment at the LHC are presented. The measurements are performed as functions of the top quark transverse momentum, the transverse momentum of the top quark-antitop quark system and the out-of-plane transverse momentum using data from pp collisions at p s = 13TeV collected by the ATLAS detector at the LHC in 2015 and corresponding to an integrated luminosity of 3.2 fb. The top quark pair events are selected in the lepton (electron or muon) + jets channel. The measured cross sections, which are compared to several predictions, allow a detailed study of top quark production.

  • 28.
    Aaboud, M.
    et al.
    Univ Mohamed Premier, Fac Sci, Oujda, Morocco.;LPTPM, Oujda, Morocco..
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    CERN, Geneva, Switzerland.
    et al.,
    Observation of Centrality-Dependent Acoplanarity for Muon Pairs Produced via Two-Photon Scattering in Pb plus Pb Collisions at root s(NN)=5.02 TeV with the ATLAS Detector2018In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 121, no 21, article id 212301Article in journal (Refereed)
    Abstract [en]

    This Letter presents a measurement of gamma gamma -> mu(+)mu(-)- production in Pb + Pb collisions recorded by the ATLAS detector at the Large Hadron Collider at root s(NN) = 5.02 TeV with an integrated luminosity of 0.49 nb(-1). The azimuthal angle and transverse momentum correlations between the muons are measured as a function of collision centrality. The muon pairs are produced from gamma gamma through the interaction of the large electromagnetic fields of the nuclei. The contribution from background sources of muon pairs is removed using a template fit method. In peripheral collisions, the muons exhibit a strong back-to-back correlation consistent with previous measurements of muon pair production in ultraperipheral collisions. The angular correlations are observed to broaden significantly in central collisions. The modifications arc qualitatively consistent with rescattering of the muons while passing through the hot matter produced in the collision.

  • 29.
    Aaboud, M.
    et al.
    Univ Mohamed Premier & LPTPM, Fac Sci, Oujda, Morocco..
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics. Royal Inst Technol, Dept Phys, Stockholm, Sweden..
    Zwalinski, L.
    CERN, Geneva, Switzerland.
    et al.,
    Search for dark matter in events with a hadronically decaying vector boson and missing transverse momentum in pp collisions at root s=13 TeV with the ATLAS detector2018In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 10, article id 180Article in journal (Refereed)
    Abstract [en]

    A search for dark matter (DM) particles produced in association with a hadronically decaying vector boson is performed using pp collision data at a centre-of-mass energy of TeV corresponding to an integrated luminosity of 36.1 fb(-1), recorded by the ATLAS detector at the Large Hadron Collider. This analysis improves on previous searches for processes with hadronic decays of W and Z bosons in association with large missing transverse momentum (mono-W/Z searches) due to the larger dataset and further optimization of the event selection and signal region definitions. In addition to the mono-W/Z search, the as yet unexplored hypothesis of a new vector boson Z produced in association with dark matter is considered (mono-Z search). No significant excess over the Standard Model prediction is observed. The results of the mono-W/Z search are interpreted in terms of limits on invisible Higgs boson decays into dark matter particles, constraints on the parameter space of the simplified vector-mediator model and generic upper limits on the visible cross sections for W/Z+DM production. The results of the mono-Z search are shown in the framework of several simplified-model scenarios involving DM production in association with the Z boson.

  • 30.
    Aaboud, M.
    et al.
    Univ Mohamed Premier, Fac Sci, Oujda, Morocco.;LPTPM, Oujda, Morocco..
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    CERN, Geneva, Switzerland.
    et al.,
    Search for heavy resonances decaying into a W or Z boson and a Higgs boson in final states with leptons and b-jets in 36 fb-1 of root s = 13 TeV pp collisions with the ATLAS detector (vol 3, 174, 2018)2018In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 11, article id 051Article in journal (Refereed)
    Abstract [en]

    A search is conducted for new resonances decaying into a W or Z boson and a 125 GeV Higgs boson in the νν¯ bb¯ , ℓ±νbb¯ , and ℓ+bb¯ final states, where ℓ± = e± or μ±, in pp collisions at s=13 TeV. The data used correspond to a total integrated luminosity of 36.1 fb−1 collected with the ATLAS detector at the Large Hadron Collider during the 2015 and 2016 data-taking periods. The search is conducted by examining the reconstructed invariant or transverse mass distributions of W h and Zh candidates for evidence of a localised excess in the mass range of 220 GeV up to 5 TeV. No significant excess is observed and the results are interpreted in terms of constraints on the production cross-section times branching fraction of heavy W and Z resonances in heavy-vector-triplet models and the CP-odd scalar boson A in two-Higgs-doublet models. Upper limits are placed at the 95% confidence level and range between 9.0 × 10−4 pb and 7.3 × 10−1 pb depending on the model and mass of the resonance.

  • 31.
    Aaboud, M.
    et al.
    Univ Mohamed Premier, Fac Sci, Oujda, Morocco.;LPTPM, Oujda, Morocco..
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    CERN, Geneva, Switzerland.
    et al.,
    Search for Higgs boson pair production in the gamma gamma b(b)over-bar final state with 13TeV pp collision data collected by the ATLAS experiment2018In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 11, article id 040Article in journal (Refereed)
    Abstract [en]

    A search is performed for resonant and non-resonant Higgs boson pair production in the final state. The data set used corresponds to an integrated luminosity of 36.1 fb(-1) of proton-proton collisions at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. No significant excess relative to the Standard Model expectation is observed. The observed limit on the non-resonant Higgs boson pair cross-section is 0.73 pb at 95% confidence level. This observed limit is equivalent to 22 times the predicted Standard Model cross-section. The Higgs boson self-coupling (=(HHH)/SM) is constrained at 95% confidence level to -8.2 < < 13.2. For resonant Higgs boson pair production through , the limit is presented, using the narrow-width approximation, as a function of m(X) in the range 260 GeV < m(X) < 1000 GeV. The observed limits range from 1.1 pb to 0.12 pb over this mass range.

  • 32.
    Aaboud, M.
    et al.
    Univ Mohamed Premier, Fac Sci, Oujda, Morocco.;LPTPM, Oujda, Morocco..
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    CERN, Geneva, Switzerland..
    et al.,
    Search for lepton-flavor violation in different-flavor, high-mass final states in pp collisions at root s=13 TeV with the ATLAS detector2018In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 98, no 9, article id 092008Article in journal (Refereed)
    Abstract [en]

    A search is performed for a heavy particle decaying into different-flavor, dilepton pairs (e mu, e tau or mu tau), using 36.1 fb(-1) of proton-proton collision data at root s = 13 TeV collected in 2015-2016 by the ATLAS detector at the Large Hadron Collider. No excesses over the Standard Model predictions are observed. Bayesian lower limits at the 95% credibility level are placed on the mass of a Z' boson, the mass of a supersymmetric tau-sneutrino, and on the threshold mass for quantum black-hole production. For the Z' and sneutrino models, upper cross-section limits are converted to upper limits on couplings, which are compared with similar limits from low-energy experiments and which are more stringent for the e tau and mu tau modes.

  • 33.
    Aaboud, M.
    et al.
    Univ Mohamed Premier, Fac Sci, Oujda, Morocco.;LPTPM, Oujda, Morocco..
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    CERN, Geneva, Switzerland..
    et al.,
    Search for lepton-flavor-violating decays of the Z boson into a r lepton and a light lepton with the ATLAS detector2018In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 98, no 9, article id 092010Article in journal (Refereed)
    Abstract [en]

    Direct searches for lepton flavor violation in decays of the Z boson with the ATLAS detector at the LHC are presented. Decays of the Z boson into an electron or muon and a hadronically decaying r lepton are considered. The searches are based on a data sample of proton-proton collisions collected by the ATLAS detector in 2015 and 2016, corresponding to an integrated luminosity of 36.1 fb(-1) at a center-of-mass energy of root s = 13 TeV. No statistically significant excess of events above the expected background is observed, and upper limits on the branching ratios of lepton-flavor-violating decays are set at the 95% confidence level: B(Z -> e tau) < 5.8 x 10(-5) and B(Z -> mu tau) < 2.4 x 10(-5). This is the first limit on B(Z -> e tau) with ATLAS data. The upper limit on 13(Z -> mu tau) is combined with a previous ATLAS result based on 20.3 fb(-1) of proton protoncollision data at a center-of-mass energy of root s = 8 TeV and the combined upper limit at 95% confidence level is B(Z -> mu tau) < 1.3 x 10(-5).

  • 34.
    Aaboud, M.
    et al.
    Univ Mohamed Premier, Fac Sci, Oujda, Morocco.;LPTPM, Oujda, Morocco..
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    CERN, Geneva, Switzerland.
    et al.,
    Search for Low-Mass Dijet Resonances Using Trigger-Level Jets with the ATLAS Detector in pp Collisions at root s=13 TeV2018In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 121, no 8, article id 081801Article in journal (Refereed)
    Abstract [en]

    Searches for dijet resonances with sub-TeV masses using the ATLAS detector at the Large Hadron Collider can be statistically limited by the bandwidth available to inclusive single-jet triggers, whose data-collection rates at low transverse momentum are much lower than the rate from standard model multijet production. This Letter describes a new search for dijet resonances where this limitation is overcome by recording only the event information calculated by the jet trigger algorithms, thereby allowing much higher event rates with reduced storage needs. The search targets low-mass dijet resonances in the range 450-1800 GeV. The analyzed data set has an integrated luminosity of up to 29.3 fb(-1) and was recorded at a center-of-mass energy of 13 TeV. No excesses are found; limits are set on Gaussian-shaped contributions to the dijet mass distribution from new particles and on a model of dark-matter particles with axial-vector couplings to quarks.

  • 35. Aaboud, M.
    et al.
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et al.,
    ATLAS Collaboration,
    Search for doubly charged Higgs boson production in multi-lepton final states with the ATLAS detector using proton–proton collisions at √s=13TeV2018In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 78, no 3Article in journal (Refereed)
    Abstract [en]

    A search for doubly charged Higgs bosons with pairs of prompt, isolated, highly energetic leptons with the same electric charge is presented. The search uses a proton–proton collision data sample at a centre-of-mass energy of 13 TeV corresponding to 36.1 fb - 1of integrated luminosity recorded in 2015 and 2016 by the ATLAS detector at the LHC. This analysis focuses on the decays H± ±→ e±e±, H± ±→ e±μ± and H± ±→ μ±μ±, fitting the dilepton mass spectra in several exclusive signal regions. No significant evidence of a signal is observed and corresponding limits on the production cross-section and consequently a lower limit on m(H± ±) are derived at 95% confidence level. With ℓ±ℓ±= e±e±/ μ±μ±/ e±μ±, the observed lower limit on the mass of a doubly charged Higgs boson only coupling to left-handed leptons varies from 770 to 870 GeV (850 GeV expected) for B(H± ±→ ℓ±ℓ±) = 100 % and both the expected and observed mass limits are above 450 GeV for B(H± ±→ ℓ±ℓ±) = 10 % and any combination of partial branching ratios.

  • 36. Aaboud, M.
    et al.
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et. al.,
    ATLAS Collaboration,
    Search for electroweak production of supersymmetric states in scenarios with compressed mass spectra at √s=13  TeV with the ATLAS detector2018In: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 97Article in journal (Refereed)
    Abstract [en]

    A search for electroweak production of supersymmetric particles in scenarios with compressed mass spectra in final states with two low-momentum leptons and missing transverse momentum is presented. This search uses proton-proton collision data recorded by the ATLAS detector at the Large Hadron Collider in 2015–2016, corresponding to 36.1  fb−1 of integrated luminosity at √s=13  TeV. Events with same-flavor pairs of electrons or muons with opposite electric charge are selected. The data are found to be consistent with the Standard Model prediction. Results are interpreted using simplified models of R-parity-conserving supersymmetry in which there is a small mass difference between the masses of the produced supersymmetric particles and the lightest neutralino. Exclusion limits at 95% confidence level are set on next-to-lightest neutralino masses of up to 145 GeV for Higgsino production and 175 GeV for wino production, and slepton masses of up to 190 GeV for pair production of sleptons. In the compressed mass regime, the exclusion limits extend down to mass splittings of 2.5 GeV for Higgsino production, 2 GeV for wino production, and 1 GeV for slepton production. The results are also interpreted in the context of a radiatively-driven natural supersymmetry model with nonuniversal Higgs boson masses.

  • 37. Aaboud, M.
    et al.
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    et al.,
    ATLAS Collaboration,
    Search for heavy ZZ resonances in the ℓ+ℓ-ℓ+ℓ- and ℓ+ℓ-v-v- final states using proton–proton collisions at √s=13 TeV with the ATLAS detector2018In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 78, no 4Article in journal (Refereed)
    Abstract [en]

    A search for heavy resonances decaying into a pair of Z bosons leading to ℓ+ℓ-ℓ+ℓ- and ℓ+ℓ- final states, where ℓ stands for either an electron or a muon, is presented. The search uses proton–proton collision data at a centre-of-mass energy of 13 TeV corresponding to an integrated luminosity of 36.1 fb - 1 collected with the ATLAS detector during 2015 and 2016 at the Large Hadron Collider. Different mass ranges for the hypothetical resonances are considered, depending on the final state and model. The different ranges span between 200 and 2000 GeV. The results are interpreted as upper limits on the production cross section of a spin-0 or spin-2 resonance. The upper limits for the spin-0 resonance are translated to exclusion contours in the context of Type-I and Type-II two-Higgs-doublet models, while those for the spin-2 resonance are used to constrain the Randall–Sundrum model with an extra dimension giving rise to spin-2 graviton excitations. 

  • 38. Aaboud, M.
    et al.
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics.
    L.Zwalinski,
    et. al.,
    Search for an invisibly decaying Higgs boson or dark matter candidates produced in association with a Z boson in pp collisions at s=13 TeV with the ATLAS detector2018In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 776, p. 318-337Article in journal (Refereed)
    Abstract [en]

    A search for an invisibly decaying Higgs boson or dark matter candidates produced in association with a leptonically decaying Z boson in proton–proton collisions at s=13 TeV is presented. This search uses 36.1 fb−1 of data collected by the ATLAS experiment at the Large Hadron Collider. No significant deviation from the expectation of the Standard Model backgrounds is observed. Assuming the Standard Model ZH production cross-section, an observed (expected) upper limit of 67% (39%) at the 95% confidence level is set on the branching ratio of invisible decays of the Higgs boson with mass mH=125 GeV. The corresponding limits on the production cross-section of the ZH process with the invisible Higgs boson decays are also presented. Furthermore, exclusion limits on the dark matter candidate and mediator masses are reported in the framework of simplified dark matter models. 

  • 39. Aaboud, M.
    et al.
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Woods, N.
    et al.,
    Combination of inclusive and differential t(t)over-bar charge asymmetry measurements using ATLAS and CMS data at root S =7 and 8 TeV2018In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 4, article id 033Article in journal (Refereed)
    Abstract [en]

    This paper presents combinations of inclusive and differential measurements of the charge asymmetry (A(C)) in top quark pair (t(t)over-bar) events with a lepton+jets signature by the ATLAS and CMS Collaborations, using data from LHC proton-proton collisions at centre-of-mass energies of 7 and 8 TeV. The data correspond to integrated luminosities of about 5 and 20 fb(-1) for each experiment, respectively. The resulting combined LHC measurements of the inclusive charge asymmetry are A(C)(LHC7) = 0.005 +/- 0.007 (stat) +/- 0.006 (syst) at 7 TeV and A(C)(LHC8) = 0.0055 +/- 0.0023 (stat) +/- 0.0025 (syst) at 8 TeV. These values, as well as the combination of A(C )measurements as a function of the invariant mass of the t(t)over-bar system at 8 TeV, are consistent with the respective standard model predictions.

  • 40. Aaboud, M.
    et al.
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    Combined measurement of differential and total cross sections in the H → γγ and the H → ZZ⁎ → 4ℓ decay channels at s=13 TeV with the ATLAS detector2018In: Vol. 786, p. 114-133Article in journal (Refereed)
    Abstract [en]

    A combined measurement of differential and inclusive total cross sections of Higgs boson production is performed using 36.1 fb−1 of 13 TeV proton–proton collision data produced by the LHC and recorded by the ATLAS detector in 2015 and 2016. Cross sections are obtained from measured H→γγ and H→ZZ⁎→4ℓ event yields, which are combined taking into account detector efficiencies, resolution, acceptances and branching fractions. The total Higgs boson production cross section is measured to be 57.0−5.9 +6.0 (stat.) −3.3 +4.0 (syst.) pb, in agreement with the Standard Model prediction. Differential cross-section measurements are presented for the Higgs boson transverse momentum distribution, Higgs boson rapidity, number of jets produced together with the Higgs boson, and the transverse momentum of the leading jet. The results from the two decay channels are found to be compatible, and their combination agrees with the Standard Model predictions.

  • 41. Aaboud, M.
    et al.
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    Search for exclusive Higgs and Z boson decays to phi gamma and rho gamma with the ATLAS detector2018In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 7, article id 127Article in journal (Refereed)
    Abstract [en]

    A search for the exclusive decays of the Higgs and Z bosons to a phi or rho meson and a photon is performed with a pp collision data sample corresponding to an integrated luminosity of up to 35.6 fb(-1) collected at root s = 13 TeV with the ATLAS detector at the CERN Large Hadron Collider. These decays have been suggested as a probe of the Higgs boson couplings to light quarks. No significant excess of events is observed above the background, as expected from the Standard Model. Upper limits at 95% confidence level were obtained on the branching fractions of the Higgs boson decays to phi gamma and rho gamma of 4.8 x 10(-4) and 8.8 x 10(-4), respectively. The corresponding 95% confidence level upper limits for the Z boson decays are 0.9 x 10(-6) and 25 x 10(-6) for phi gamma and rho gamma, respectively.

  • 42.
    Aaboud, M.
    et al.
    Univ Mohamed Premier, Fac Sci, Oujda, Morocco.;LPTPM, Oujda, Morocco..
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics. Royal Inst Technol, Dept Phys, Stockholm, Sweden..
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics. Royal Inst Technol, Dept Phys, Stockholm, Sweden..
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics. Royal Inst Technol, Dept Phys, Stockholm, Sweden..
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics. Royal Inst Technol, Dept Phys, Stockholm, Sweden..
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics. Royal Inst Technol, Dept Phys, Stockholm, Sweden..
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics. Royal Inst Technol, Dept Phys, Stockholm, Sweden..
    Zwalinski, L.
    CERN, Geneva, Switzerland..
    Search for the Higgs boson produced in association with a vector boson and decaying into two spin-zero particles in the H -> aa -> 4b channel in pp collisions at root s=13 TeV with the ATLAS detector2018In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 10, article id 031Article in journal (Refereed)
    Abstract [en]

    A search for exotic decays of the Higgs boson into a pair of spin-zero particles, H -> aa, where the a-boson decays into b-quarks promptly or with a mean proper lifetime c tau(a) up to 6 mm and has a mass in the range of 20-60GeV, is presented. The search is performed in events where the Higgs boson is produced in association with a W or Z boson, giving rise to a signature of one or two charged leptons (electrons or muons) and multiple jets from b-quark decays. The analysis is based on the dataset of proton-proton collisions at root s = 13TeV recorded in 2015 and 2016 by the ATLAS detector at the CERN Large Hadron Collider, corresponding to an integrated luminosity of 36: 1 fb(-1). No significant excess of events above the Standard Model background prediction is observed, and 95% confidence-level upper limits are derived for the production cross-sections for pp -> WH, ZH and their combination, times the branching ratio of the decay chain H -> aa -> 4b. For a-bosons which decay promptly, the upper limit on the combination of cross-sections for WH and ZH times the branching ratio of H -> aa -> 4b ranges from 3.0 pb for m(a) = 20 GeV to 1.3 pb for m(a) = 60 GeV, assuming that the ratio of WH to ZH cros-ssections follows the Standard Model prediction. For a-bosons with longer proper lifetimes, the most stringent limits are 1.8 pb and 0.68 pb, respectively, at c tau(a) similar to 0.4 mm.

  • 43. Aaboud, M.
    et al.
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    ATLAS Collaboration,
    et. al.,
    Search for additional heavy neutral Higgs and gauge bosons in the ditaufinal state produced in 36 fb(-1) of pp collisions at root s=13 TeV withthe ATLAS detector2018In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, article id 055Article in journal (Refereed)
    Abstract [en]

    A search for heavy neutral Higgs bosons and Z' bosons is performed using a data sample corresponding to an integrated luminosity of 36.1 fb(-1) from proton-proton collisions at root s = 13 TeV recorded by the ATLAS detector at the LHC during 2015 and 2016. The heavy resonance is assumed to decay to tau(+)tau(-) with at least one tau lepton decaying to final states with hadrons and a neutrino. The search is performed in the mass range of 0.2-2.25 TeV for Higgs bosons and 0.2-4.0 TeV for Z' bosons. The data are in good agreement with the background predicted by the Standard Model. The results are interpreted in benchmark scenarios. In the context of the hMSSM scenario, the data exclude tan beta > 1.0 for m(A) = 0.25 TeV and tan beta > 42 for m(A) = 1.5 TeV at the 95% confidence level. For the Sequential Standard Model, Z'(SSM) with m(Z') < 2.42 TeV is excluded at 95% confidence level, while Z'(NU) with m(Z') < 2.25 TeV is excluded for the non-universal G(221) model that exhibits enhanced couplings to third-generation fermions.

  • 44. Aaboud, M.
    et al.
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    ATLAS Collaboration,
    et. al.,
    Search for heavy resonances decaying into WW in the e nu mu nu final state in pp collisions at root s=13 TeV with the ATLAS detector2018In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 78, no 1Article in journal (Refereed)
    Abstract [en]

    A search for neutral heavy resonances is performed in the WW -> e nu mu nu decay channel using pp collision data corresponding to an integrated luminosity of 36.1 fb(-1), collected at a centre-of-mass energy of 13 TeV by the ATLAS detector at the Large Hadron Collider. No evidence of such heavy resonances is found. In the search for production via the quark-antiquark annihilation or gluon-gluon fusion process, upper limits on sigma(X) x B(X -> WW) as a function of the resonance mass are obtained in the mass range between 200 GeV and up to 5 TeV for various benchmark models: a Higgs-like scalar in different width scenarios, a two-Higgs-doublet model, a heavy vector triplet model, and a warped extra dimensions model. In the vector-boson fusion process, constraints are also obtained on these resonances, as well as on a Higgs boson in the Georgi-Machacek model and a heavy tensor particle coupling only to gauge bosons.

  • 45. Aaboud, M
    et al.
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    A search for resonances decaying into a Higgs boson and a new particle X in the XH -> qqbb final state with the ATLAS detector2018In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 779, p. 24-45Article in journal (Refereed)
    Abstract [en]

    A search for heavy resonances decaying into a Higgs boson (H) and a new particle (X) is reported, utilizing 36.1 fb(-1) of proton-proton collision data at root s = 13 TeV collected during 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. The particle Xis assumed to decay to a pair of light quarks, and the fully hadronic final state XH -> q (q) over bar 'b (b) over bar is analysed. The search considers the regime of high XH resonance masses, where the X and H bosons are both highly Lorentz-boosted and are each reconstructed using a single jet with large radius parameter. A two-dimensional phase space of XH mass versus X mass is scanned for evidence of a signal, over a range of XH resonance mass values between 1 TeV and 4 TeV, and for X particles with masses from 50 GeV to 1000 GeV. All search results are consistent with the expectations for the background due to Standard Model processes, and 95% CL upper limits are set, as a function of XH and X masses, on the production cross-section of the XH -> q (q) over bar 'b (b) over bar resonance.

  • 46. Aaboud, M.
    et al.
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Combination of searches for heavy resonances decaying into bosonic and leptonic final states using 36 fb(-1) of proton-proton collision data at root s=13 TeV with the ATLAS detector2018In: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 98, no 5, article id 052008Article in journal (Refereed)
    Abstract [en]

    Searches for new heavy resonances decaying into different pairings of W, Z, or Higgs bosons, as well as dirffiffiffiectly into leptons, are presented using a data sample corresponding to 36.1 fb(-1) of pp collisions at root s = 13 TeV collected during 2015 and 2016 with the ATLAS detector at the CERN Large Hadron Collider. Analyses selecting bosonic decay modes in the qqqq, vvqq, evqq, eeqq, evev, eevv, evee, eeee, qqbb, vvbb, evbb, and eebb final states are combined, searching for a narrow-width resonance. Likewise, analyses selecting the leptonic ev and ee final states are also combined. These two sets of analyses are then further combined. No significant deviation from the Standard Model predictions is observed. Three benchmark models are tested: a model predicting the existence of a new heavy scalar singlet, a simplified model predicting a heavy vector-boson triplet, and a bulk Randall-Sundrum model with a heavy spin-2 Kaluza-Klein excitation of the graviton. Cross section limits are set at the 95% confidence level using an asymptotic approximation and are compared with predictions for the benchmark models. These limits are also expressed in terms of constraints on couplings of the heavy vector-boson triplet to quarks, leptons, and the Higgs boson. The data exclude a heavy vector-boson triplet with mass below 5.5 TeV in a weakly coupled scenario and 4.5 TeV in a strongly coupled scenario, as well as a Kaluza-Klein graviton with mass below 2.3 TeV.

  • 47. Aaboud, M.
    et al.
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Direct top-quark decay width measurement in the t(t)over-bar lepton+jetschannel at root s=8 TeV with the ATLAS experiment2018In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 78, no 2, article id 129Article in journal (Refereed)
    Abstract [en]

    This paper presents a direct measurement of the decay width of the top quark using t (t) over bar events in the lepton+jets final state. The data sample was collected by the ATLAS detector at the LHC in proton-proton collisions at a centre-of-mass energy of 8 TeV and corresponds to an integrated luminosity of 20.2 fb(-1). The decay width of the top quark is measured using a template fit to distributions of kinematic observables associated with the hadronically and semileptonically decaying top quarks. The result, Gamma(t) = 1.76 +/- 0.33 (stat.) (+0.79)(-0.68) (syst.) GeV for a top-quark mass of 172.5 GeV, is consistent with the prediction of the Standard Model.

  • 48. Aaboud, M.
    et al.
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Measurement of differential cross-sections of a single top quark produced in association with a W boson at root s=13TeV with ATLAS2018In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 78, no 3, article id 186Article in journal (Refereed)
    Abstract [en]

    The differential cross-section for the production of a W boson in association with a top quark is measured for several particle-level observables. The measurements are performed using 36.1 fb(-1) of pp collision data collected with the ATLAS detector at the LHC in 2015 and 2016. Differential cross-sections are measured in a fiducial phase space defined by the presence of two charged leptons and exactly one jet matched to a b-hadron, and are normalised with the fiducial cross-section. Results are found to be in good agreement with predictions from several Monte Carlo event generators.

  • 49. Aaboud, M
    et al.
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L.
    et al.,
    Measurement of inclusive and differential cross sections in the H -> ZZ* -> 4l decay channel in pp collisions at root s=13 TeV with the ATLAS detector2017In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 10, article id 132Article in journal (Refereed)
    Abstract [en]

    Inclusive and differential fiducial cross sections of Higgs boson production in proton-proton collisions are measured in the H -> Z Z* -> 4l decay channel. The proton-proton collision data were produced at the Large Hadron Collider at a centre-of-mass energy of 13 TeV and recorded by the ATLAS detector in 2015 and 2016, corresponding to an integrated luminosity of 36.1 fb(-1). The inclusive fiducial cross section in the H -> Z Z* -> 4l decay channel is measured to be 3.62 +/- 0.50 (stat) (+0.25)(-0.20) (sys) fb, in agreement with the Standard Model prediction of 2.91 +/- 0.13 fb. The cross section is also extrapolated to the total phase space including all Standard Model Higgs boson decays. Several differential fiducial cross sections are measured for observables sensitive to the Higgs boson production and decay, including kinematic distributions of jets produced in association with the Higgs boson. Good agreement is found between data and Standard Model predictions. The results are used to put constraints on anomalous Higgs boson interactions with Standard Model particles, using the pseudo-observable extension to the kappa-framework.

  • 50. Aaboud, M
    et al.
    Kastanas, Konstatinos A.
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Lund-Jensen, Bengt
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ohm, Christian
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Ripellino, Giulia
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Sidebo, P. Edvin
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Strandberg, Jonas
    KTH, School of Engineering Sciences (SCI), Physics, Particle and Astroparticle Physics.
    Zwalinski, L
    et al.,
    Measurement of inclusive jet and dijet cross-sections in proton-proton collisions at root s=13 TeV with the ATLAS detector2018In: Journal of High Energy Physics (JHEP), ISSN 1126-6708, E-ISSN 1029-8479, no 5, article id 195Article in journal (Refereed)
    Abstract [en]

    Inclusive jet and dijet cross-sections are measured in proton-proton collisions at a centre-of-mass energy of 13 TeV. The measurement uses a dataset with an integrated luminosity of 3.2 fb(-1) recorded in 2015 with the ATLAS detector at the Large Hadron Collider. Jets are identified using the anti-lit algorithm with a radius parameter value of R = 0.4. The inclusive jet cross-sections are measured double-differentially as a function of the jet transverse momentum, covering the range from 100 GeV to 3.5 TeV, and the absolute jet rapidity up to vertical bar y vertical bar = 3. The double-differential dijet production cross-sections are presented as a function of the dijet mass, covering the range from 300 GeV to 9 TeV, and the half absolute rapidity separation between the two leading jets within vertical bar y vertical bar < 3, y*, up to y* = 3. Next-to-leading-order, and next-to-next-to-leading-order for the inclusive jet measurement, perturbative QCD calculations corrected for non-perturbative and electroweak effects are compared to the measured cross-sections.

1234567 1 - 50 of 106186
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