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• 1551.
KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. Oskar Klein Centre for Cosmoparticle Physics, Sweden .
LPSC, UJF Grenoble 1, CNRS/IN2P3, INP de Grenoble, France. Department of Physics, Stockholm University. Oskar Klein Centre for Cosmoparticle Physics, Sweden.
Constraints on cosmic-ray propagation and acceleration models from recent data2011Inngår i: Proceedings of the 32nd International Cosmic Ray Conference, ICRC 2011, Institute of High Energy Physics , 2011, Vol. 6, s. 228-231Konferansepaper (Fagfellevurdert)

We are studying the constraints obtained on transport and acceleration mechanisms of galactic cosmic rays by using statistical tools in combination with the propagation package GALPROP and recent PAMELA data. Using only PAMELA data allows us to avoid inconsistencies between data sets from different experiments, minimise uncertainties on solar modulation parameters, and have a complementary and precise data set on (anti-)matter as well as primary and secondary nuclei over 3 orders of magnitude in energy. This allows us to simultaneously place strong constraints on cosmic-ray propagation and acceleration models. We describe our methodology and present some preliminary results in this paper.

• 1552. Wu, X.
KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
PANGU: A Wide Field Gamma-Ray Imager and Polarimeter2016Inngår i: SPACE TELESCOPES AND INSTRUMENTATION 2016: ULTRAVIOLET TO GAMMA RAY, SPIE - International Society for Optical Engineering, 2016, artikkel-id UNSP 99056EKonferansepaper (Fagfellevurdert)

PANGU (the PAir-productioN Gamma-ray Unit) is a gamma-ray telescope with a wide field of view optimized for spectro-imaging, timing and polarization studies. It will map the gamma-ray sky from 10 MeV to a few GeV with unprecedented spatial resolution. This window on the Universe is unique to detect photons produced directly by relativistic particles, via the decay of neutral pions, or the annihilation or decay light from anti-matter and the putative light dark matter candidates. A wealth of questions can be probed among the most important themes of modern physics and astrophysics. The PANGU instrument is a pair-conversion gamma-ray telescope based on an innovative design of a silicon strip tracker. It is light, compact and accurate. It consists of 100 layers of silicon micro-strip detectors of 80 x 80 cm(2) in area, stacked to height of about 90 cm, and covered by an anticoincidence detectors. PANGU relies on multiple scattering effects for energy measurement, reaching an energy resolution between 30-50% for 10 MeV - 1GeV. The novel tracker will allow the first polarization measurement and provide the best angular resolution ever obtained in the soft gamma ray and GeV band.

• 1553. Wuf, X.
KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
PANGU: A high resolution gamma-ray space telescope2015Inngår i: Proceedings of Science, Proceedings of Science (PoS) , 2015Konferansepaper (Fagfellevurdert)

PANGU (the PAir-productioN Gamma-ray Unit) is a small astrophysics mission with wide field of view optimized for spectro-imaging, timing and polarisation studies. It will map the gamma-ray sky from 10 MeV to a few GeV with unprecedented spatial resolution. This window on the Universe is unique to detect photons emitted directly by relativistic particles, via the decay of neutral pions, or the annihilation or decay light from anti-matter and the putative light dark matter candidates. A wealth of questions can be probed among the most important themes of modern physics and astrophysics. The PANGU instrument is a pair-conversion gamma-ray telescope based on an innovative design of a silicon strip tracker. It is light, compact and accurate. It consists of 100 layers of silicon micro-strip detector of 40 x 40 cm2 in area, stacked to height of about 90 cm, and covered by a top anticoincidence detector. PANGU relies on multiple scattering effects for energy measurement, reaching an energy resolution between 30-50% for 10 MeV - 1 GeV. The novel tracker will allow the first polarisation measurement and provide the best angular resolution ever obtained in the soft gamma ray and GeV band. PANGU has been proposed to the recent ESA-CAS Call for Joint Small Science Mission. In this contribution, the key science objectives, the payload concept and the expected performance will be presented.

• 1554.
KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. AlbaNova Univ Ctr, Oskar Klein Ctr Cosmoparticle Phys, S-10691 Stockholm, Sweden..
KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. AlbaNova Univ Ctr, Oskar Klein Ctr Cosmoparticle Phys, S-10691 Stockholm, Sweden.
A Study of Background Conditions for Sphinx-The Satellite-Borne Gamma-Ray Burst Polarimeter2018Inngår i: Galaxies, E-ISSN 2075-4434, Vol. 6, nr 2, artikkel-id 50Artikkel i tidsskrift (Fagfellevurdert)

SPHiNX is a proposed satellite-borne gamma-ray burst polarimeter operating in the energy range 50-500 keV. The mission aims to probe the fundamental mechanism responsible for gamma-ray burst prompt emission through polarisation measurements. Optimising the signal-to-background ratio for SPHiNX is an important task during the design phase. The Geant4 Monte Carlo toolkit is used in this work. From the simulation, the total background outside the South Atlantic Anomaly (SAA) is about 323 counts/s, which is dominated by the cosmic X-ray background and albedo gamma rays, which contribute similar to 60% and similar to 35% of the total background, respectively. The background from albedo neutrons and primary and secondary cosmic rays is negligible. The delayed background induced by the SAA-trapped protons is about 190 counts/s when SPHiNX operates in orbit for one year. The resulting total background level of similar to 513 counts/s allows the polarisation of similar to 50 GRBs with minimum detectable polarisation less than 30% to be determined during the two-year mission lifetime.

• 1555.
KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik. KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik. KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
Multistep shell model description of spin-aligned neutron-proton pair coupling2012Inngår i: Nuclear Physics A, ISSN 0375-9474, E-ISSN 1873-1554, Vol. 877, s. 51-58Artikkel i tidsskrift (Fagfellevurdert)

The recently proposed spin-aligned neutron-proton pair coupling scheme is studied within a non-orthogonal basis in term of the multistep shell model. This allows us to identify simultaneously the roles played by other configurations such as the normal pairing term. The model is applied to four-, six- and eight-hole N = Z nuclei below the core Sn-100.

• 1556.
KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik. KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
Multistep shell model in the complex energy plane2012Inngår i: Advanced Many-Body And Statistical Methods In Mesoscopic Systems, Institute of Physics Publishing (IOPP), 2012, s. 012029-Konferansepaper (Fagfellevurdert)

We have adopted the multistep shell model in the complex energy plane to study nuclear excitations occurring in the continuum part of the spectrum. In this method one proceeds by solving the shell model equations in a successive manner. That is, in each step one constructs the building blocks to be used in future steps. We applied this formalism to analyze the unbound nuclei Li-12,Li-13 starting from the one - particle states in Li-10 and two - particle states in Li-11. In the former case the excitations correspond to the motion of three particles partitioned as the product of a one - particle and two - particle systems. The ground state of Li-12 is thus calculated to be an antibound (virtual) state. In the four - particle system Li-13 the states can be constructed as the coupling of two correlated pairs. We found that there is no bound or antibound state in Li-13.

• 1557.
KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik. GANIL, France. GANIL, France. GANIL, France. KTH, Skolan för teknikvetenskap (SCI), Fysik, Kärnfysik.
Analysis of the unbound spectrum of 12Li.2011Inngår i: Nuclear Physics A, ISSN 0375-9474, E-ISSN 1873-1554, Vol. 850, s. 53-68Artikkel i tidsskrift (Fagfellevurdert)

The unbound nucleus 12Li is evaluated by studying three-neutron one-proton excitations within the multistepshell model in the complex energy plane. It is found that the ground state of this system consists of anantibound 2− state. A number of narrow states at low energy are found which ensue from the coupling ofresonances in 11Li to continuum states close to threshold.

• 1558.
Tokyo Metropolitan Univ, Dept Phys, 1-1 Minami Osawa, Hachioji, Tokyo 1920397, Japan..
KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. Tokyo Metropolitan Univ, Dept Phys, 1-1 Minami Osawa, Hachioji, Tokyo 1920397, Japan.. Tokyo Metropolitan Univ, Dept Phys, 1-1 Minami Osawa, Hachioji, Tokyo 1920397, Japan.. Tokyo Metropolitan Univ, Dept Phys, 1-1 Minami Osawa, Hachioji, Tokyo 1920397, Japan.. Tokyo Metropolitan Univ, Dept Phys, 1-1 Minami Osawa, Hachioji, Tokyo 1920397, Japan.. NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.;Lawrence Livermore Natl Lab, 7000 East Ave, Livermore, CA 94550 USA.. NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.;Lawrence Livermore Natl Lab, 7000 East Ave, Livermore, CA 94550 USA.. NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.;Lawrence Livermore Natl Lab, 7000 East Ave, Livermore, CA 94550 USA.. NASA, Goddard Space Flight Ctr, 8800 Greenbelt Rd, Greenbelt, MD 20771 USA.;Lawrence Livermore Natl Lab, 7000 East Ave, Livermore, CA 94550 USA.. Yale Univ, Dept Phys, POB 208120, New Haven, CT 06520 USA.. Yale Univ, Dept Phys, POB 208120, New Haven, CT 06520 USA..
Poisson vs. Gaussian statistics for sparse X-ray data: Application to the soft X-ray spectrometer2019Inngår i: Publications of the Astronomical Society of Japan, ISSN 0004-6264, E-ISSN 2053-051X, Vol. 71, nr 4, artikkel-id 75Artikkel i tidsskrift (Fagfellevurdert)

Reliable results when fitting X-ray data require proper consideration of the statistics involved. We probe the impact of Gaussian versus Poisson statistics at low count levels using both the standard chi(2) method and maximum likelihood based on Poisson studied and quantified through simulated spectra with known properties. We then test the results through analysis of Mn K alpha calibration data taken with the flight spare microcalorimeter for the Hitomi soft X-ray spectrometer. Through comparison with simulations, our results show that the chi(2) method tends to give overly optimistic estimates of the detector energy resolution, in particular when there are few counts. Given an energy resolution of similar to 5eV and a line with about 100 photons, the line width becomes similar to 10% lower in the chi(2) method than in Poisson statistics. This is a consequence of the uncertainties being dominated by counting statistics, and therefore highlights the need to choose the appropriate fit statistic.

• 1559.
KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
Annihilation Lines from Dark Matter with the Fermi-LAT2010Inngår i: Invisible Universe International Conference, 2010, s. 463-467Konferansepaper (Fagfellevurdert)

Dark matter is today one of the most intriguing but so far unresolved issues in physics. Many extensions of the Standard Model of particle physics predict a stable Weakly Interacting Massive Particle (WIMP) that may annihilate directly into two gamma-rays. If the WIMPs are non-relativistic, the gamma-rays from this channel will have an energy equal to the mass of the WIMP. The signature caused by this annihilation is a spectral line, smeared out only by the energy resolution of the detector. The signal would be a "smoking gun" for dark matter, since no other astrophysical source should be able to produce it. We present here the preliminary results from the search for a dark matter line on a limited data set from the Fermi Large Area Telescope (LAT), the main instrument onboard the Fermi Gamma-ray Space Telescope, which was successfully launched on June 11, 2008. The Fermi-LAT is a pair-conversion detector for gamma-rays with an energy range from 20 MeV to 300 GeV and has an unprecedented resolution and sensitivity.

• 1560.
KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
Search for Gamma-ray Lines from Dark Matter with the Fermi Large Area Telescope2010Doktoravhandling, monografi (Annet vitenskapelig)

Dark matter (DM) constitutes one of the most intriguing but so far unresolved issues in physics. In many extensions of the Standard Model of particle physics, the existence of a stable Weakly Interacting Massive Particle (WIMP) is predicted. The WIMP is an excellent DM particle candidate. One of the most interesting scenarios is the creation of monochromatic gamma-rays from the annihilation or decay of these particles. This type of signal would represent a “smoking gun” for DM, since no other known astrophysical process should be able to produce it.

In this thesis, the search for spectral lines with the Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope (Fermi) is presented. The satellite was successfully launched from Cape Canaveral in Florida, USA, on 11 June, 2008. The energy resolution and performance of the detector are both key factors in the search and are investigated here using beam test data, taken at CERN in 2006 with a scaled-down version of the Fermi-LAT instrument. A variety of statistical methods, based on both hypothesis tests and confidence interval calculations, are then reviewed and tested in terms of their statistical power and coverage.

A selection of the statistical methods are further developed into peak finding algorithms and applied to a simulated data set called obssim2, which corresponds to one year of observations with the Fermi-LAT instrument, and to almost one year of Fermi-LAT data in the energy range 20–300 GeV. The analysis on Fermi-LAT data yielded no detection of spectral lines, so limits are placed on the velocity-averaged cross-section, $<\sigma v>_{\gamma X}$, and the decay lifetime, $\tau_{\gamma X}$, and theoretical implications are discussed.

• 1561.
KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
Towards detecting lines from dark matter annihilations with GLAST2008Licentiatavhandling, monografi (Annet vitenskapelig)

Dark matter (DM) constitutes one of the most intriguing but so far unresolved issues in physics. In many extensions of the Standard Model of particle physics, the existence of a stable Weakly Interacting Massive Particle (WIMP) is predicted. The WIMP is an excellent DM particle candidate and one of the most interesting scenarios include an annihilation of two WIMPs into two gamma-rays. If the WIMPs are assumed to be non-relativistic, the resulting photons will both have an energy equal to the mass of the WIMP and will manifest themselves as a monochromatic spectral line in the energy spectrum. This type of signal would represent a “smoking gun” for DM, since no other known astrophysical process should be able to produce it. When searching for a line, the energy resolution and performance of the calorimeter are key factors. In this thesis, these are investigated using beam test data, taken at CERN in 2006. Four statistical methods that can be used to search for DM spectral lines are, then, studied in terms of their power and coverage. The methods are based on both hypothesis tests and confidence interval calculations. Two peak finding methods are also tested on a simulated data set representing one year of realistic data, obtained with the Large Area Telescope (LAT) on-board the Gamma-ray Large Area Space Telescope (GLAST). The data set is called Service Challenge 2 (SC2) and contains a variety of gamma-ray sources, including different DM components. Finally, an upper limit on < σν > γγ, based on SC2, is calculated.

• 1562. Yu, Hoi-Fung
KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
Synchrotron cooling in energetic gamma-ray bursts observed by the Fermi Gamma-Ray Burst Monitor2015Inngår i: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 573, artikkel-id A81Artikkel i tidsskrift (Fagfellevurdert)

Context. We study the time-resolved spectral properties of energetic gamma-ray bursts (GRBs) with good high-energy photon statistics observed by the Gamma-Ray Burst Monitor ((IBM) onboard the Fermi Gamma-Ray Space Telescope. Aims. We aim to constrain in detail the spectral properties of GRB prompt emission on a time-resolved basis and to discuss the theoretical implications of the fitting results in the context of various prompt emission models. Methods. Our sample comprises eight GRBs observed by the Fermi (IBM in its first five years of mission, with 1 keV-1 MeV fluence f > 1.0 x 10(-4) erg cm(-2) and a signal-to-noise ratio level of S/N >= 10.0 above 900 keV. We performed a time-resolved spectral analysis using a variable temporal binning technique according to optimal S/N criteria, resulting in a total of 299 time-resolved spectra. We performed Band function fits to all spectra and obtained the distributions for the low-energy power-lay index alpha, the high-energy power-law index beta, the peak energy in the observed nu F-nu, spectrum E-p, and the difference between the low- and high-energy power-law indices Delta s = alpha-beta. We also applied a physically motivated synchrotron model, which is a triple power-law with constrained power-law indices and a blackbody component, to test the prompt emission for consistency with a synchrotron origin and obtain the distributions for the two break energies E-b,E-1 and E-b,E-2 the middle segment power-law index beta, and the Planck function temperature kT. Results. The Band function parameter distributions are alpha = -0.73(-0.21)(+0.16), beta = -2.13(-0.56)(+0.28), E-p = 374.47(-187.7)(+307.3) keV (log(10) E-p = 2.577(-0.30)(+0.26)), and Delta s = 1.38(-0.31)(+0.54), with average errors sigma(alpha) similar to 0.1, sigma(beta) similar to 0.2, and sigma(Ep) similar to 0.1E(p). Using the distributions of Delta s and beta, the electron population index p is found to be consistent with the "moderately fast" scenario, in which fast- and slow-cooling scenarios cannot be distinguished. The physically motivated synchrotron-fitting function parameter distributions are E-b,E-1 = 129.6(-32.4)(+132.2) keV, E-b,E-2 = 631.4(-309.6)(+582) keV, beta = 1.721(-0.25)(+0.48), and kT = 10.4(-3.7)(+4.9) keV, with average errors sigma(beta) similar to 0.2, sigma E-b,E-1 similar to 0.1E(b,1), sigma E-b,E-2 similar to 0.4E(b,2,) and sigma(kT) similar to 0.1kT. This synchrotron function requires the synchrotron injection and cooling break (i.e., E-min and E-cool) to be close to each other within a factor of ten, often in addition to a Planck function. Conclusions. A synchrotron model is found that is consistent with most of the time-resolved spectra for eight energetic Fermi (IBM bursts with good high-energy photon statistics as long as both the cooling and injection break are included and the leftmost spectral slope is lifted either by including a thermal component or when an evolving magnetic field is accounted for.

• 1563. Yurkin, Yu.T.
KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Energi- och ugnsteknik.
Trapped antiprotons in the Earth inner radiation belt in PAMELA experiment2011Inngår i: Bulletin of the Russian Academy of Sciences: Physics, ISSN 1062-8738, Vol. 75, nr 6, s. 854-856Artikkel i tidsskrift (Fagfellevurdert)

The existence of trapped antiprotons in the Earth's inner radiation belt has been theoretically predicted, but not observed. We present a procedure for antiproton selection and the observation results from the PAMELA space experiment measurements. The PAMELA magnetic spectrometer ensures reliable identification of particles and charge signs, value determination, and energy measurement, thus enabling us to experimentally establish the existence of antiprotons trapped in the Earth's inner radiation belt.

• 1564. Zaconte, V.
KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
ALTEA: flight model calibration at GSI2006Inngår i: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 37, nr 9, s. 1704-1709Artikkel i tidsskrift (Fagfellevurdert)

The ALTEA project, an international and multi-disciplinary collaboration scheduled to fly in the International Space Station (ISS) after July 2006, is aimed at studying particle radiation in space environment and its effects on astronauts, in particular the anomalous perception of 'light flashes'. In this paper, we present experimental results obtained by testing the Flight Model of the ALTEA particle detector in two measurement sessions performed at the heavy ion accelerator of GSI laboratory in Darmstadt, Germany. Instrument response was compared with Monte-carlo simulations to study its linearity and calculate amplification.

• 1565. Zane, Silvia
KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
The on-board calibration system of the X-ray Imaging Polarimetry Explorer (XIPE)2016Inngår i: SPACE TELESCOPES AND INSTRUMENTATION 2016: ULTRAVIOLET TO GAMMA RAY, SPIE - International Society for Optical Engineering, 2016, artikkel-id UNSP 99054HKonferansepaper (Fagfellevurdert)

The calibration system for XIPE is aimed at providing a way to check and correct possible variations of performance of the Gas Pixel Detector during the three years of operation in orbit (plus two years of possible extended operation), while facilitating the observation of the celestial sources. This will be performed by using a filter wheel with a large heritage having a set of positions for the calibration and the observation systems. In particular, it will allow for correcting possible gain variation, for measuring the modulation factor using a polarized source, for removing non interesting bright sources in the field of view and for observing very bright celestial sources. The on-board calibration system is composed of three filter wheels, one for each detector and it is expected to operate for a small number of times during the year. Moreover, since it operates once at a time, within the observation mode, it allows for simultaneous calibration and acquisition from celestial sources on different detectors. In this paper we present the scope and the requirements of the on-board calibration system, its design, and a description of its possible use in space.

• 1566. Zhang, S. -N
KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
Introduction to the high energy cosmic-radiation detection (HERD) facility onboard China's future space station2017Inngår i: Proceedings of Science, Sissa Medialab Srl , 2017Konferansepaper (Fagfellevurdert)

The High Energy cosmic-Radiation Detection (HERD) facility is one of several space astronomy payloads onboard China's Space Station, which is planned for operation starting around 2025 for about 10 years. The main scientific objectives of HERD are searching for signals of dark matter annihilation products, precise cosmic electron (plus positron) spectrum and anisotropy measurements up to 10 TeV, precise cosmic ray spectrum and composition measurements up to the knee energy, and high energy gamma-ray monitoring and survey. HERD is composed of a 3-D cubic calorimeter (CALO) surrounded by microstrip silicon trackers (STKs) from five sides except the bottom. CALO is made of about 7,500 cubes of LYSO crystals, corresponding to about 55 radiation lengths and 3 nuclear interaction lengths, respectively. The top STK microstrips of six X-Y layers are sandwiched with tungsten converters to make precise directional measurements of incoming electrons and gamma-rays. In the baseline design, each of the four side STKs is made of only three layers microstrips. All STKs will also be used for measuring the charge and incoming directions of cosmic rays, as well as identifying back scattered tracks. With this design, HERD can achieve the following performance: energy resolution of 1% for electrons and gamma-rays beyond 100 GeV and 20% for protons from 100 GeV to 1 PeV; electron/proton separation power better than 10-5; effective geometrical factors of &gt;3 m2sr for electron and diffuse gamma-rays, &gt;2 m2sr for cosmic ray nuclei. R&amp;D is under way for reading out the LYSO signals with optical fiber coupled to image intensified IsCMOS and CALO prototype of 250 LYSO crystals.

• 1567. Zhang, S. N.
KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
The high energy cosmic-radiation detection (HERD) facility onboard China's Space Station2014Inngår i: Proceedings of SPIE - The International Society for Optical Engineering, 2014Konferansepaper (Fagfellevurdert)

The High Energy cosmic-Radiation Detection (HERD) facility is one of several space astronomy payloads of the cosmic lighthouse program onboard China's Space Station, which is planned for operation starting around 2020 for about 10 years. The main scientific objectives of HERD are indirect dark matter search, precise cosmic ray spectrum and composition measurements up to the knee energy, and high energy gamma-ray monitoring and survey. HERD is composed of a 3-D cubic calorimeter (CALO) surrounded by microstrip silicon trackers (STKs) from five sides except the bottom. CALO is made of about 104 cubes of LYSO crystals, corresponding to about 55 radiation lengths and 3 nuclear interaction lengths, respectively. The top STK microstrips of seven X-Y layers are sandwiched with tungsten converters to make precise directional measurements of incoming electrons and gamma-rays. In the baseline design, each of the four side SKTs is made of only three layers microstrips. All STKs will also be used for measuring the charge and incoming directions of cosmic rays, as well as identifying back scattered tracks. With this design, HERD can achieve the following performance: energy resolution of 1% for electrons and gamma-rays beyond 100 GeV, 20% for protons from 100 GeV to 1 PeV; electron/proton separation power better than 10-5; effective geometrical factors of &gt;3 m2sr for electron and diffuse gamma-rays, &gt;2 m2sr for cosmic ray nuclei. R and D is under way for reading out the LYSO signals with optical fiber coupled to image intensified CCD and the prototype of one layer of CALO. © 2014 SPIE.

• 1568.
SUNY Stony Brook, Dept Chem, Stony Brook, NY 11794 USA..
KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik. CERN, Geneva, Switzerland..
Flow fluctuations in Pb plus Pb collisions at root s(NN)=5.02 TeV with the ATLAS detector2019Inngår i: Nuclear Physics A, ISSN 0375-9474, E-ISSN 1873-1554, Vol. 982, s. 323-326Artikkel i tidsskrift (Fagfellevurdert)

Measurements of four-particle cumulants c(n){4} for n = 1, 2, 3, 4 are presented using 470 mu b(-1) of Pb+Pb collisions at root s(NN) = 5.02 TeV with the ATLAS detector at the LHC. These cumulants provide information on the event-by-event fluctuations of single harmonics p(v(n)). For the first time, a negative c(1){4} is observed. The c(4){4} is found to be negative in central collisions but changes sign around 20-25% centrality. This behavior is consistent with a nonlinear contribution to v(4) that is proportional to v(2)(2). c(2){4} and c(3){4} are calculated using two reference event classes in order to investigate the influence of volume fluctuations. Over most of the centrality range, c(2){4} and c(3){4} are found to be negative, while in the ultra-central collisions, c(2){4} changes sign and becomes positive, suggesting a deviation from Gaussian behavior in the event-by-event fluctuation of v(2). The magnitudes of the sign change are also found to be dependent of the event class definition .

• 1569. Řípa, J.
KTH, Skolan för teknikvetenskap (SCI), Fysik, Partikel- och astropartikelfysik.
Cosmological effects on the observed flux and fluence distributions of gamma-ray bursts2011Konferansepaper (Fagfellevurdert)

Several claims have been put forward that an essential fraction of long-duration BATSE gamma-ray bursts should lie at redshifts larger than 5. This point-of-view follows from the natural assumption that fainter objects should, on average, lie at larger redshifts. However, redshifts larger than 5 are rare for bursts observed by Swift. The purpose of this article is to show that the most distant bursts in general need not be the faintest ones. We derive the cosmological relationships between the observed and emitted quantities, and arrive at a prediction that is tested on the ensembles of BATSE, Swift and Fermi bursts. This analysis is independent on the assumed cosmology, on the observational biases, as well as on any gamma-ray burst model. We arrive to the conclusion that apparently fainter bursts need not, in general, lie at large redshifts. Such a behaviour is possible, when the luminosities (or emitted energies) in a sample of bursts increase more than the dimming of the observed values with redshift. In such a case dP(z)/dz > 0 can hold, where P(z) is either the peak-flux or the fluence. This also means that the hundreds of faint, long-duration BATSE bursts need not lie at high redshifts, and that the observed redshift distribution of long Swift bursts might actually represent the actual distribution.

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