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  • 101.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    A brief status of non-standard neutrino interactions2013In: NOW 2012: Proceedings of the Neutrino Oscillation Workshop / [ed] Paolo Bernardini, Gianluigi Fogli, Eligio Lisi, Elsevier, 2013, p. 301-307Conference paper (Refereed)
    Abstract [en]

    In this plenary talk, we review the status of non-standard neutrino interactions (NSIs). First, we give a brief introduction to neutrino flavor transitions with NSIs based on the standard paradigm of neutrino oscillations. Then, we discuss alternative scenarios for neutrino flavor transitions such as neutrino decoherence, neutrino decay, and NSIs. Second, we investigate NSIs with three neutrino flavors. In general, we introduce production and detection NSIs, including the so-called zero-distance effect, and matter NSIs. In addition, we study mappings and approximate formulas for NSIs. Third, we present a brief account of theoretical models for NSIs. Fourth and most important, we investigate in detail the phenomenology of NSIs based on different types of data from neutrino experiments. Fifth, we give some phenomenological bounds on both matter and production/detection NSIs as well as we present sensitivity and discovery reach of NSIs at future experiments. Finally, we present a summary and state our conclusions.

  • 102.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    After Higgs2012In: New scientist (1971), ISSN 0262-4079, Vol. 215, no 2881, p. 29-29Article in journal (Other (popular science, discussion, etc.))
  • 103.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Another collider is not the way forward2013In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 494, no 7435, p. 35-35Article in journal (Other academic)
  • 104.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Bimaximal fermion mixing from the quark and leptonic mixing matrices2005In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 622, no 02-jan, p. 159-164Article in journal (Refereed)
    Abstract [en]

    In this Letter. we show how the mixing angles of the standard parameterization add when multiplying the quark and leptonic mixing matrices. i.e., we derive explicit sum rules for the quark and leptonic mixing angles. In this connection, we also discuss other recently proposed sum rules for the mixing angles assuming bimaximal fermion mixing. In addition, we find that the present experimental and phenomenological data of the mixing angles naturally fulfill our sum rules, and thus, give rise to bilarge or bimaximal fermion mixing.

  • 105.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Cutting with Occam's razor2012In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 86, no 9, p. 097301-Article in journal (Refereed)
    Abstract [en]

    We comment positively on the recent article "Seesaw mechanism with Occam's razor" [K. Harigaya et al. Phys. Rev. D 86, 013002 (2012).] by Harigaya, Ibe, and Yanagida. In this article, the authors are using the principle of Occam's razor in neutrino physics-a principle that should be applied more often in science in general. At the end, we also discuss the Bayesian method in statistics, in which Occam's razor is naturally built in.

  • 106.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Don't let furore over neutrinos blur results2012In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 485, no 7398, p. 309-309Article in journal (Refereed)
  • 107.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Effects of Non-Standard Interactions in the MINOS Experiment2008In: Neutrino Factories, Superbeams And Betabeams / [ed] Osamu Yasuda, Naba Mondal, Chihiro Ohmori, 2008, p. 213-215Conference paper (Refereed)
    Abstract [en]

    In this talk, we investigate the effects of non-standard interactions (NSI) in the MINOS experiment based on a full three-flavor neutrino oscillation framework simulation. The simulation was performed using the GLoBES software. The results indicate that the allowed region in the sin(2)(2 theta(23))-Delta m(31)(2) plane is extended due to NSI effects, that there is a degeneracy between the leptonic mixing angle theta(13) and the NSI parameter epsilon(e tau), and that MINOS can put a lower upper bound on sin(2)(2 theta(13)) than CHOOZ only for small values of vertical bar epsilon(e tau)vertical bar.

  • 108.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Extrinsic CPT Violation in Neutrino Oscillations2004In: NEUTRINO FACTORIES AND SUPERBEAMS: 5th International Workshop on Neutrino Factories and Superbeams; NuFact 03 / [ed] Adam Para, Fermi National Accelerator Laboratory, American Institute of Physics , 2004, p. 265-268Conference paper (Refereed)
    Abstract [en]

    In this talk, we investigate extrinsic CPT violation in neutrino oscillations in matter with three flavors. Note that extrinsic CPT violation is different from intrinsic CPT violation. Extrinsic CPT violation is one way of quantifying matter effects, whereas intrinsic CPT violation would mean that the CPT invariance theorem is not valid. We present analytical formulas for the extrinsic CPT probability differences and discuss their implications for long-baseline experiments and neutrino factory setups.

  • 109.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Four's a crowd2013In: New scientist (1971), ISSN 0262-4079, Vol. 219, no 2925, p. 32-32Article in journal (Refereed)
  • 110.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    International Linear Collider: Another collider is not the way forward2013In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 494, no 7435Article in journal (Refereed)
  • 111.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    LHC reality check2012In: New scientist (1971), ISSN 0262-4079, Vol. 216, no 2895, p. 36-36Article in journal (Other academic)
  • 112.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Neutrino extras2012In: New scientist (1971), ISSN 0262-4079, Vol. 216, no 2885, p. 31-31Article in journal (Other (popular science, discussion, etc.))
  • 113.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Neutrinos and the hunt for the last mixing angle2012In: Europhysics News, ISSN 0531-7479, Vol. 43, no 4, p. 22-25Article in journal (Refereed)
    Abstract [en]

    In summary, the measurement of Ξ 23 by the Super-Kamiokande experiment resulted in one of the first indications of physics beyond Standard Model, the measurement of Ξ 12 was the first precision measurement in neutrino physics, and the hunt for the value of the third and final mixing angle Ξ 13 was the beginning of the end of the measurements of the mixing angles for the neutrinos, but the beginning of the continuation of measurements of the remaining neutrino parameters.

  • 114.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Neutrinos from Kaluza-Klein Dark Matter Annihilations in the Sun2011In: Physics beyond the Standard Models of Particles, Cosmology and Astrophysics: Proceedings of the Fifth International Conference / [ed] H V Klapdor-Kleingrothaus, I V Krivosheina, R Viollier, World Scientific Publishing , 2011, p. 496-502Conference paper (Refereed)
    Abstract [en]

    In this talk, we compute fluxes of neutrinos from Kaluza–Klein dark matter annihilations in the Sun based on cross-sections from both five- and six-dimensional models. For our numerical calculations, we use WimpSim and DarkSUSY. In addition, we compare our results with the ones derived earlier in the literature.

  • 115.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Neutrinos from WIMP Annihilations2008In: Dark Matter in Astroparticle and Particle Physics - Dark 2007: Proceedings of the 6th International Heidelberg Conference / [ed] Hans Volker Klapdor-Kleingrothaus, Geraint F. Lewis, World Scientific Publishing , 2008, p. 51-59Conference paper (Refereed)
    Abstract [en]

    In this talk, we make an improved analysis on the production of neutrinos coming from WIMP annihilations inside the Sun as well as the Earth. We treat both neutrino interaction and oscillation effects in aconsistent three-flavor framework. Our numerical simulations are performed in an event-based setting, which is useful for both theoretical studies and creating neutrino telescope Monte Carlo simulations. We find that the yield of muon-type neutrinos is enhanced or suppressed depending on the dominant WIMP annihilation channel. In addition, we find that oscillations can significantly affect the neutrino yields from WIMP annihilations in the Sun. Effectively, the neutrino flavors are mixed. Finally, for the Earth, the oscillations have no large impact at energies for the new neutrino telescopes such as IceCube, ANTARES, and NESTOR.

  • 116.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Non-Hermitian neutrino oscillations in matter with PT symmetric Hamiltonians2016In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 113, no 6, article id 61001Article in journal (Refereed)
    Abstract [en]

    We introduce and develop a novel approach to extend the ordinary two-flavor neutrino oscillation formalism in matter using a non-Hermitian PT symmetric effective Hamiltonian. The condition of PT symmetry is weaker and less mathematical than that of hermicity, but more physical, and such an extension of the formalism can give rise to sub-leading effects in neutrino flavor transitions similar to the effects by so-called non-standard neutrino interactions. We derive the necessary conditions for the spectrum of the effective Hamiltonian to be real as well as the mappings between the fundamental and effective parameters. We find that the real spectrum of the effective Hamiltonian will depend on all new fundamental parameters introduced in the non-Hermitian PT symmetric extension of the usual neutrino oscillation formalism and that either i) the spectrum is exact and the effective leptonic mixing must always be maximal or ii) the spectrum is approximate and all new fundamental parameters must be small.

  • 117.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Non-standard neutrino interactions2009In: SIXTH INTERNATIONAL WORKSHOP ON NEUTRINO-NUCLEUS INTERACTIONS IN THE FEW-GEV REGION / [ed] Sanchez F; Sorel M; Alvarez-Ruso L; Cervera A; Vicente-Vacas M, American Institute of Physics , 2009, Vol. 1189, p. 16-23Conference paper (Refereed)
    Abstract [en]

    In this talk, I will review non-standard interactions in neutrino physics, especially I will emphazise the impact of non-standard interactions on neutrino oscillations. First, I will give a brief introduction about non-standard interactions and what they are. Then, I will present what has been performed in the literature, what I have done in the field, and what could be done in the future. Next, I will discuss how important non-standard interactions are for neutrino cross-sections. Finally, I will give a summary of the field.

  • 118.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Preprint servers: Follow arXiv's lead2012In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 489, no 7416, p. 367-Article in journal (Refereed)
  • 119.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Relativistic Quantum Physics: From Advanced Quantum Mechanics to Introductory Quantum Field Theory2011 (ed. 1)Book (Refereed)
    Abstract [en]

    Quantum physics and special relativity theory were two of the greatest breakthroughs in physics during the twentieth century and contributed to paradigm shifts in physics. This book combines these two discoveries to provide a complete description of the fundamentals of relativistic quantum physics, guiding the reader effortlessly from relativistic quantum mechanics to basic quantum field theory. The book gives a thorough and detailed treatment of the subject, beginning with the classification of particles, the Klein–Gordon equation and the Dirac equation. It then moves on to the canonical quantization procedure of the Klein–Gordon, Dirac and electromagnetic fields. Classical Yang–Mills theory, the LSZ formalism, perturbation theory, elementary processes in QED are introduced, and regularization, renormalization and radiative corrections are explored. With exercises scattered through the text and problems at the end of most chapters, the book is ideal for advanced undergraduate and graduate students in theoretical physics.

  • 120.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Searches for hyperbolic extra dimensions at the LHC2008Other (Refereed)
    Abstract [en]

    In this poster, we present a model of large extra dimensions where the internal space has the geometry of a hyperbolic disc. Compared with the ADD model, this model provides a more satisfactory solution to the hierarchy problem between the electroweak scale and the Planck scale, and it also avoids constraints from astrophysics. Since there is no known analytic form of the Kaluza-Klein spectrum for our choice of geometry, we obtain a spectrum based on a combination of approximations and numerical computations. We study the possible signatures of our model for hadron colliders, especially the LHC, where the most important processes are the production of a graviton together with a hadronic jet or a photon. We find that for the case of hadronic jet production, it is possible to obtain relatively strong signals, while for the case of photon production, this is much more difficult.

  • 121.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Status of non-standard neutrino interactions2013In: Reports on progress in physics (Print), ISSN 0034-4885, E-ISSN 1361-6633, Vol. 76, no 4, p. 044201-Article, review/survey (Refereed)
    Abstract [en]

    The phenomenon of neutrino oscillations has been established as the leading mechanism behind neutrino flavor transitions, providing solid experimental evidence that neutrinos are massive and lepton flavors are mixed. Here we review sub-leading effects in neutrino flavor transitions known as non-standard neutrino interactions (NSIs), which is currently the most explored description for effects beyond the standard paradigm of neutrino oscillations. In particular, we report on the phenomenology of NSIs and their experimental and phenomenological bounds as well as an outlook for future sensitivity and discovery reach.

  • 122.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Sterile search2013In: New scientist (1971), ISSN 0262-4079, Vol. 218, no 2913, p. 32-32Article in journal (Refereed)
  • 123.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Testing CPT invariance with neutrinos2002In: Proceedings of ICHEP 2002 / [ed] S. Bentvelsen, P. de Jong, J. Koch, and E. Laenen, Amsterdam: Elsevier Science B.V. , 2002, p. 53-56Conference paper (Refereed)
    Abstract [en]

    We investigate possible tests of CPT invariance on the level of event rates at neutrino factories. We do not assume any specific model, but phenomenological differences in the neutrino-antineutrino masses and mixing angles in a Lorentz invariance preserving context, which could be induced by physics beyond the Standard Model. We especially focus on the muon neutrino and antineutrino disappearance channels in order to obtain constraints on the neutrino-antineutrino mass and mixing angle differences. In a typical neutrino factory setup simulation, we find, for example, that

    .

  • 124.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    T-violating effects in three flavor neutrino oscillations in matter2001In: International Europhysics Conference on High Energy Physics: hep2001 / [ed] Horváth Dezsõ (chairman), Lévai Péter, Patkós András, SISSA , 2001, p. 195-Conference paper (Refereed)
    Abstract [en]

    In this talk, we consider the interplay of fundamental and matter-induced T-violating effects in neutrino oscillations in matter. We present a simple approximative analytical formula for the T-violating probability asymmetry for three flavor neutrino oscillations in matter with an arbitrary density profile. We also discuss some implications of the obtained results. Since there are no T-violating effects in two flavor neutrino case (in the limit of vanshing $\theta_{13}$ or $\Delta m_{21}^2$, the three flavor neutrino oscillations reduces to the two flavor ones), the T-violating probability asymmetry can, in principle, provide a way to measure $\theta_{13}$ and $\Delta m_{21}^2$.

  • 125.
    Ohlsson, Tommy
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Popa, Christoph
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Zhang, He
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Non-unitarity of the leptonic mixing matrix in the TeV-scale type-I seesaw model2010In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 692, no 4, p. 257-260Article in journal (Refereed)
    Abstract [en]

    The non-unitarity effects in leptonic flavor mixing are regarded as one of the generic features of the type-1 seesaw model. Therefore, we explore these effects in the TeV-scale type-1 seesaw model, and show that there exist non-trivial correlations among the non-unitarity parameters, stemming from the typical flavor structure of the low-scale seesaw model. In general, it follows from analytical discussions and numerical results that all the six non-unitarity parameters are related to three model parameters, while the widely studied parameters eta(e tau) and eta(mu tau) cannot be phenomenologically significant simultaneously.

  • 126.
    Ohlsson, Tommy
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Riad, Stella
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Running of neutrino parameters and the Higgs self-coupling in a six-dimensional UED model2013In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 718, no 3, p. 1002-1007Article in journal (Refereed)
    Abstract [en]

    We investigate a six-dimensional universal extra-dimensional model in the extension of an effective neutrino mass operator. We derive the β-functions and renormalization group equations for the Yukawa couplings, the Higgs self-coupling, and the effective neutrino mass operator in this model. Especially, we focus on the renormalization group running of physical parameters such as the Higgs self-coupling and the leptonic mixing angles. The recent measurements of the Higgs boson mass by the ATLAS and CMS Collaborations at the LHC as well as the current three-flavor global fits of neutrino oscillation data have been taken into account. We set a bound on the six-dimensional model, using the vacuum stability criterion, that allows five Kaluza-Klein modes only, which leads to a strong limit on the cutoff scale. Furthermore, we find that the leptonic mixing angle θ12 shows the most sizeable running, and that the running of the angles θ13 and θ23 are negligible. Finally, it turns out that the findings in this six-dimensional model are comparable with what is achieved in the corresponding five-dimensional model, but the cutoff scale is significantly smaller, which means that it could be detectable in a closer future.

  • 127.
    Ohlsson, Tommy
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Schwetz, Thomas
    Zhang, He
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Non-standard neutrino interactions in the Zee-Babu model2009In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 681, no 3, p. 269-275Article in journal (Refereed)
    Abstract [en]

    We investigate non-standard neutrino interactions (NSIs) in the Zee-Babu model. The size of NSIs predicted by this model is obtained from a full scan over the parameter space. taking into account constraints from low-energy experiments such as searches for lepton flavor violation (LFV) and the requirement to obtain a viable neutrino mass matrix. The dependence on the scale of new physics as well as on the type of the neutrino mass hierarchy is discussed. We find that NSIs at the source of a future neutrino factory may be at an observable level in the nu(e) -> nu(tau) and/or nu(mu) -> nu(tau) channels. In particular, if the doubly charged scalar of the model has a mass in reach of the LHC and if the neutrino mass hierarchy is inverted, a highly predictive scenario is obtained with observable signals at the LHC, in upcoming neutrino oscillation experiments, in LFV processes, and for NSIs at a neutrino factory.

  • 128.
    Ohlsson, Tommy
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Zhang, He
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Non-standard interaction effects at reactor neutrino experiments2009In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 671, no 1, p. 99-104Article in journal (Refereed)
    Abstract [en]

    We study non-standard interactions (NSIs) at reactor neutrino experiments, and in particular, the mimicking effects on theta(13). We present generic formulas for oscillation probabilities including NSIs from sources and detectors. Instructive mappings between the fundamental leptonic mixing parameters and the effective leptonic mixing parameters are established. In addition, NSI corrections to the mixing angles theta(13) and theta(12) are discussed in detailed. Finally, we show that, even for a vanishing theta(13), all Oscillation phenomenon may still be observed ill future short baseline reactor neutrino experiments, such as Double Chooz and Daya Bay, due to the existences of NSIs.

  • 129.
    Ohlsson, Tommy
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Zhang, He
    Zhou, Shun
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Effects of nonstandard neutrino interactions at PINGU2013In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 88, no 1, p. 013001-Article in journal (Refereed)
    Abstract [en]

    Neutrino oscillation experiments in the past decades have greatly improved our knowledge on neutrinos by measuring the fundamental neutrino parameters. The ongoing and upcoming neutrino oscillation experiments are intended to pin down the neutrino mass hierarchy and to discover the leptonic CP violation. By means of neutrino oscillograms, we analyze the impact of nonstandard neutrino interactions on neutrino oscillations in Earth matter. The standard neutrino oscillation probabilities may be significantly changed by nonstandard interaction parameters, and, in particular, the CP-violating effects in the energy range E = 1-20 GeV are greatly enhanced. In addition, the event rates of muon neutrinos in the proposed huge atmospheric neutrino experiment, PINGU at the South Pole, have been estimated in the presence of nonstandard neutrino interactions. It has been found that the PINGU experiment has very good sensitivities to the nonstandard neutrino interaction parameters.

  • 130.
    Ohlsson, Tommy
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Zhang, He
    Zhou, Shun
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Nonstandard interaction effects on neutrino parameters at medium-baseline reactor antineutrino experiments2014In: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 728, p. 148-155Article in journal (Refereed)
    Abstract [en]

    Precision measurements of leptonic mixing parameters and the determination of the neutrino mass hierarchy are the primary goals of the forthcoming medium-baseline reactor antineutrino experiments, such as JUNO and RENO-50. In this work, we investigate the impact of nonstandard neutrino interactions (NSIs) on the measurements of {sin(2) theta(12), Delta m(21)(2)} and {sin(2) theta(13), Delta m(31)(2)}. and on the sensitivity to the neutrino mass hierarchy, at the medium-baseline reactor experiments by assuming a typical experimental setup. It turns out that the true mixing parameter sin(2) theta(12) can be excluded at a more than 3 sigma level if the NSI parameter epsilon(e mu), or epsilon(e tau), is as large as 2% in the most optimistic case. However, the discovery reach of NSI effects has been found to be small, and depends crucially on the CP-violating phases. Finally, we show that NSI effects could enhance or reduce the discrimination power of the JUNO and RENO-50 experiments between the normal and inverted neutrino mass hierarchies.

  • 131.
    Ohlsson, Tommy
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Zhang, He
    Zhou, Shun
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Probing the leptonic Dirac CP-violating phase in neutrino oscillation experiments2013In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 87, no 5, p. 053006-Article in journal (Refereed)
    Abstract [en]

    The discovery of leptonic CP violation is one of the primary goals of next-generation neutrino oscillation experiments, which is feasible due to the recent measurement of a relatively large leptonic mixing angle theta(13). We suggest two new working observables Delta A(alpha beta)(m) equivalent to max[A(alpha beta)(CP)(delta) - min[A(alpha beta)(CP)(delta)] and Delta A(alpha beta)(CP)(delta) equivalent to A(alpha beta)(CP)(delta) - A(alpha beta)(CP)(0) to describe the CP-violating effects in long-baseline and atmospheric neutrino oscillation experiments. The former signifies the experimental sensitivity to the leptonic Dirac CP-violating phase delta and can be used to optimize the experimental setup, while the latter measures the intrinsic leptonic CP violation and can be used to extract delta directly from the experimental observations. Both analytical and numerical analyses are carried out to illustrate their main features. It turns out that an intense neutrino beam with sub-GeV energies and a baseline of a few 100 km may serve as an optimal experimental setup for probing leptonic CP violation.

  • 132.
    Ohlsson, Tommy
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Zhang, He
    Zhou, Shun
    KTH, School of Engineering Sciences (SCI), Theoretical Physics.
    Radiative corrections to the leptonic Dirac CP-violating phase2013In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 87, no 1, p. 013012-Article in journal (Refereed)
    Abstract [en]

    Since the smallest leptonic mixing angle theta(13) has been measured to be relatively large, it is quite promising to constrain or determine the leptonic Dirac CP-violating phase delta in future neutrino oscillation experiments. Given some typical values of delta = pi/2, pi, and 3 pi/2 at the low energy scale, as well as current experimental results of the other neutrino parameters, we perform a systematic study of radiative corrections to delta by using the one-loop renormalization group equations in the minimal supersymmetric standard model and the universal extra-dimensional model. It turns out that delta is rather stable against radiative corrections in both models, except for the minimal supersymmetric standard model with a very large value of tan beta. Both cases of Majorana and Dirac neutrinos are discussed. In addition, we use the preliminary indication of delta = (1.08(-0.31)(+0.28))pi or delta = (1.67(-0.77)(+0.37))pi from the latest global-fit analyses of data from neutrino oscillation experiments to illustrate how it will be modified by radiative corrections.

  • 133.
    Ohlsson, Tommy
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Zhou, Shun
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics. Chinese Acad Sci,China.
    Renormalization group running of neutrino parameters2014In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 5, p. 5153-Article, review/survey (Refereed)
    Abstract [en]

    Neutrinos are the most elusive particles in our Universe. They have masses at least one million times smaller than the electron mass, carry no electric charge and very weakly interact with other particles, meaning that they are rarely captured in terrestrial detectors. Tremendous efforts in the past two decades have revealed that neutrinos can transform from one type to another as a consequence of neutrino oscillations-a quantum mechanical effect over macroscopic distances-yet the origin of neutrino masses remains puzzling. The physical evolution of neutrino parameters with respect to energy scale may help elucidate the mechanism for their mass generation.

  • 134.
    Riad, Stella
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Running of Neutrino Parameters in Extra Dimensions2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
  • 135.
    Riad, Stella
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Studies of effective theories beyond the Standard Model2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    The vast majority of all experimental results in particle physics can be described by the Standard Model (SM) of particle physics. However, neither the existence of neutrino masses nor the mixing in the leptonic sector, which have been observed, can be described within this model. In fact, the model only describes a fraction of the known energy in the Universe. Thus, we know there must exist a theory beyond the SM. There is a plethora of possible candidates for such a model, such as supersymmetry, extra dimensional theories, and string theory. So far, there are no evidence in favor of these models.

    These theories often reside at high energies, and will therefore be manifest as effective theories at the low energies experienced here on Earth. A first example in extra-dimensional theories. From our four-dimensional point of view, particles which propagate through the extra dimensions will effectivel be perceived as towers of heavy particles. In this thesis we consider an extra-dimensional model with universal extra dimensions, where all SM particles are allowed to propagate through the extra dimensions. Especially, we place a bound on the range of validity for this model. We study the renormalization group running of the leptonic parameters as well as the Higgs self-coupling in this model with the neutrino masses generated by a Weinberg operator.

    Grand unified theories, where the gauge couplings of the SM are unified into a single oe at some high energy scale, are motivated by the electroweak unification. The unification must necessarily take place at energies many orders of magnitude greater than those that ever can be achieved on Earth. In order to make sense of the theoru, ehich is given at the grand unified scale, at the electroweak scale, the symmetry at the grand unified scale is broken down to the SM symmetry. Within these models the SM is considered as an effective field theory. We study renormalization group running of the leptonic parameters in a non-supersymmetric SO(10) model which is broken in two steps via the Pati-Salam group.

    Finally, the discovery of the new boson at the LHC provides a new opportunity to search for physics beyond the SM. We consider an effective model where the magnitudes of the couplings in the Higgs sector are scaled by so-called coupling scale factors. We perform Bayesian parameter inference based on the LHC data. Furthermore, we perform Bayesian model comparison, comparing models where one or several of the Higgs couplings are allowed, to the SM, where the couplings are fixed.

  • 136. Scott, Pat
    et al.
    Sivertsson, Sofia
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Gamma Rays from Ultracompact Primordial Dark Matter Minihalos2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 103, no 21, p. 211301-1-211301-4Article in journal (Refereed)
    Abstract [en]

    Ultracompact minihalos have been proposed as a new class of dark matter structure. They would be produced by phase transitions in the early Universe or features in the inflaton potential, and constitute nonbaryonic massive compact halo objects today. We examine the prospects of detecting these minihalos in gamma rays if dark matter can self-annihilate. We compute present-day fluxes from minihalos produced in the e(+)e(-) annihilation epoch and the QCD and electroweak phase transitions. Even at a distance of 4 kpc, minihalos from the e(+)e(-) epoch would be eminently detectable today by the Fermi satellite or air Ccerenkov telescopes, or even in archival EGRET data. Within 2 kpc, they would appear as extended sources to Fermi. At 4 kpc, minihalos from the QCD transition have similar predicted fluxes to dwarf spheroidal galaxies, so might also be detectable by present or upcoming experiments.

  • 137.
    Sivertsson, Sofia
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Dark matter in and around stars2009Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    There is by now compelling evidence that most of the matter in the universe is in the form of dark matter, a form of matter quite different from the matter we experience in every day life. The gravitational effects of this dark matter have been observed in many different ways but its true nature is still unknown. In most models dark matter particles can annihilate with each other into standard model particles. The direct or indirect observation of such annihilation products could give important clues for the dark matter puzzle. For signals from dark matter annihilations to be detectable, typically high dark matter densities are required. Massive objects, such as stars, can increase the local dark matter density both via scattering off nucleons and by pulling in dark matter gravitationally as the star forms. Dark matter annihilations outside the star would give rise to gamma rays and this is discussed in the first paper. Furthermore dark matter annihilations inside the star would deposit energy inside the star which, if abundant enough, could alter the stellar evolution. Aspects of this are investigated in the second paper. Finally, local dark matter overdensities formed in the early universe could still be around today; prospects of detecting gamma rays from such clumps are discussed in the third paper.

  • 138.
    Sivertsson, Sofia
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Studies of dark matter in and around stars2012Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    There is by now compelling evidence that most of the matter in the Universe is in the form of dark matter, a form of matter quite different from the matter we experience in every day life. The gravitational effects of this dark matter have been observed in many different ways but its true nature is still unknown. In most models, dark matter particles can annihilate with each other into standard model particles; the direct or indirect observation of such annihilation products could give important clues for the dark matter puzzle. For signals from dark matter annihilations to be detectable, typically high dark matter densities are required. Massive objects, such as stars, can increase the local dark matter density both via scattering off nucleons and by pulling in dark matter gravitationally as a star forms. Annihilations within this kind of dark matter population gravitationally bound to a star, like the Sun, give rise to a gamma ray flux. For a star which has a planetary system, dark matter can become gravitationally bound also through gravitational interactions with the planets. The interplay between the different dark matter populations in the solar system is analyzed, shedding new light on dark matter annihilations inside celestial bodies and improving the predicted experimental reach. Dark matter annihilations inside a star would also deposit energy in the star which, if abundant enough, could alter the stellar evolution. This is investigated for the very first stars in the Universe. Finally, there is a possibility for abundant small scale dark matter overdensities to have formed in the early Universe. Prospects of detecting gamma rays from such minihalos, which have survived until the present day, are discussed.

  • 139.
    Sivertsson, Sofia
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Edsjö, Joakim
    Department of Physics, Stockholm University.
    Accurate calculations of the WIMP halo around the Sun and prospects for gamma ray detection2008In: Identification of dark matter 2008: idm2008, SISSA , 2008, p. 112-Conference paper (Refereed)
    Abstract [en]

    Weakly interacting massive particles (WIMPs) can be captured by heavenly objects, like the Sun.Under the process of being captured by the Sun, they will build up a population of WIMPs aroundit, that will eventually sink to the core of the Sun. It has been argued with simpler estimatesbefore that this halo of WIMPs around the Sun could be a strong enough gamma ray source to bea detectable signature for WIMP dark matter. We here revisit the problem using detailed MonteCarlo simulations and detailed composition and structure information about the Sun to estimatethe size of the gamma ray flux. Compared to earlier estimates, we find that the gamma ray fluxfrom WIMP annihilations in the Sun halo would be negligible and no current or planned detectorswould even be able to detect this flux.

  • 140.
    Sivertsson, Sofia
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Edsjö, Joakim
    Accurate calculations of the WIMP halo around the Sun and prospects for its gamma-ray detection2010In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 81, no 6, p. 063502-1-063502-14Article in journal (Refereed)
    Abstract [en]

    Galactic weakly interacting massive particles (WIMPs) may scatter off solar nuclei to orbits gravitationally bound to the Sun. Once bound, the WIMPs continue to lose energy by repeated scatters in the Sun, eventually leading to complete entrapment in the solar interior. While the density of the bound population is highest at the center of the Sun, the only observable signature of WIMP annihilations inside the Sun is neutrinos. It has been previously suggested that although the density of WIMPs just outside the Sun is lower than deep inside, gamma rays from WIMP annihilation just outside the surface of the Sun, in the so-called WIMP halo around the Sun, may be more easily detected. We here revisit this problem using detailed Monte Carlo simulations and detailed composition and structure information about the Sun to estimate the size of the gamma-ray flux. Compared to earlier simpler estimates, we find that the gamma-ray flux from WIMP annihilations in the solar WIMP halo would be negligible; no current or planned detectors would be able to detect this flux.

  • 141.
    Sivertsson, Sofia
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Edsjö, Joakim
    Stockholm University.
    WIMP diffusion in the Solar System including solar WIMP-nucleon scattering2012In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 85, no 12, p. 123514-Article in journal (Refereed)
    Abstract [en]

    Dark matter in the form of Weakly Interacting Massive Particles (WIMPs) can be captured by the Sun and the Earth, sink to their cores, annihilate and produce neutrinos that can be searched for with neutrino telescopes. The calculation of the capture rates of WIMPs in the Sun and especially the Earth are affected by large uncertainties coming mainly from effects of the planets in the Solar System, reducing the capture rates by up to an order of magnitude (or even more in some cases). We show that the WIMPs captured by weak scatterings in the Sun also constitute an important bound WIMP population in the Solar System. Taking this population and its interplay with the population bound through gravitational diffusion into account cancel the planetary effects on the capture rates, and the capture essentially proceeds as if the Sun and the Earth were free in the galactic halo. The neutrino signals from the Sun and the Earth are thus significantly higher than claimed in the scenarios with reduced capture rates.

  • 142.
    Sivertsson, Sofia
    et al.
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Gandolo, Paolo
    The WIMP capture process for dark stars in the early universe2011In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 729, no 1, p. 51-1-51-11Article in journal (Refereed)
    Abstract [en]

    The first stars to form in the universe may have been dark stars, powered by dark matter annihilation instead of nuclear fusion. The initial amount of dark matter gathered by the star gravitationally can sustain it only for a limited period of time. It has been suggested that capture of additional dark matter from the environment can prolong the dark star phase even to the present day. Here we show that this capture process is ineffective to prolong the life of the first generation of dark stars. We construct a Monte-Carlo simulation that follows each Weakly Interacting Massive Particle (WIMP) in the dark matter halo as its orbit responds to the formation and evolution of the dark star, as it scatters off the star's nuclei, and as it annihilates inside the star. A rapid depletion of the WIMPs on orbits that cross the star causes the demise of the first generation of dark stars. We suggest that a second generation of dark stars may in principle survive much longer through capture. We comment on the effect of relaxing our assumptions.

  • 143. Wildner, E.
    et al.
    Baussan, E.
    Blennow, Mattias
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Bogomilov, M.
    Burgman, A.
    Bouquerel, E.
    Carlile, C.
    Cederkall, J.
    Christiansen, P.
    Cupial, P.
    Danared, H.
    Dracos, M.
    Ekelof, T.
    Eshraqi, M.
    Hall-Wilton, R.
    Koutchouk, J. -P
    Lindroos, M.
    Martini, M.
    Matev, R.
    McGinnis, D.
    Miyamoto, R.
    Ohlsson, Tommy
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Ohman, H.
    Olvegard, M.
    Ruber, R.
    Schonauer, H.
    Tang, J. Y.
    Tsenov, R.
    Vankova-Kirilova, G.
    Vassilopoulos, N.
    The Opportunity Offered by the ESSnuSB Project to Exploit the Larger Leptonic CP Violation Signal at the Second Oscillation Maximum and the Requirements of This Project on the ESS Accelerator Complex2016In: Advances in High Energy Physics, ISSN 1687-7357, E-ISSN 1687-7365, article id 8640493Article in journal (Refereed)
    Abstract [en]

    The European Spallation Source (ESS), currently under construction in Lund, Sweden, is a research center that will provide, by 2023, the world's most powerful neutron source. The average power of the proton linac will be 5 MW. Pulsing this linac at higher frequency will make it possible to raise the average total beam power to 10 MW to produce, in parallel with the spallation neutron production, a very intense neutrino Super Beam of about 0.4 GeV mean neutrino energy. This will allow searching for leptonic CP violation at the second oscillation maximum where the sensitivity is about 3 times higher than at the first. The ESS neutrino Super Beam, ESSnuSB operated with a 2.0 GeV linac proton beam, together with a large undergroundWater Cherenkov detector located at 540 km from Lund, will make it possible to discover leptonic CP violation at 5 sigma. significance level in 56% (65% for an upgrade to 2.5 GeV beam energy) of the leptonic CP-violating phase range after 10 years of data taking, assuming a 5% systematic error in the neutrino flux and 10% in the neutrino cross section. The paper presents the outstanding physics reach possible for CP violation with ESSnuSB obtainable under these assumptions for the systematic errors. It also describes the upgrade of the ESS accelerator complex required for ESSnuSB.

  • 144. Zackrisson, Erik
    et al.
    Scott, Pat
    Rydberg, Claes-Erik
    Iocco, Fabio
    Edvardsson, Bengt
    Ostlin, Goran
    Sivertsson, Sofia
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Zitrin, Adi
    Broadhurst, Tom
    Gondolo, Paolo
    Finding high-redshift dark stars with the James Webb Space Telescope2010In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 717, no 1, p. 257-267Article in journal (Refereed)
    Abstract [en]

    The first stars in the history of the universe are likely to form in the dense central regions of similar to 10(5)-10(6) M-circle dot cold dark matter halos at z approximate to 10-50. The annihilation of dark matter particles in these environments may lead to the formation of so-called dark stars, which are predicted to be cooler, larger, more massive, and potentially more long-lived than conventional population III stars. Here, we investigate the prospects of detecting high-redshift dark stars with the upcoming James Webb Space Telescope (JWST). We find that all dark stars with masses up to 10(3) M-circle dot are intrinsically too faint to be detected by JWST at z > 6. However, by exploiting foreground galaxy clusters as gravitational telescopes do, certain varieties of cool (T-eff <= 30,000 K) dark stars should be within reach at redshifts up to z approximate to 10. If the lifetimes of dark stars are sufficiently long, many such objects may also congregate inside the first galaxies. We demonstrate that this could give rise to peculiar features in the integrated spectra of galaxies at high redshifts, provided that dark stars make up at least similar to 1% of the total stellar mass in such objects.

  • 145. Zackrisson, Erik
    et al.
    Scott, Pat
    Rydberg, Claes-Erik
    Iocco, Fabio
    Sivertsson, Sofia
    KTH, School of Engineering Sciences (SCI), Theoretical Physics, Theoretical Particle Physics.
    Östlin, Göran
    Mellema, Garrelt
    Iliev, Ilian T.
    Shapiro, Paul R.
    Observational constraints on supermassive dark stars2010In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 407, no 1, p. L74-L78Article in journal (Refereed)
    Abstract [en]

    Some of the first stars could be cooler and more massive than standard stellar models would suggest, due to the effects of dark matter annihilation in their cores. It has recently been argued that such objects may attain masses in the 10(4)-10(7) M-circle dot range and that such supermassive dark stars should be within reach of the upcoming James Webb Space Telescope. Notwithstanding theoretical difficulties with this proposal, we argue here that some of these objects should also be readily detectable with both the Hubble Space Telescope and ground-based 8-10 m class telescopes. Existing survey data already place strong constraints on 10(7) M-circle dot dark stars at z approximate to 10. We show that such objects must be exceedingly rare or short lived to have avoided detection.

123 101 - 145 of 145
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