| 1. |
- Baldini, L., et al.
(författare)
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Preliminary results of the LAT Calibration Unit beam tests
- 2007
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Ingår i: First GLAST Symposium. - Melville : American Institute of Physics (AIP). - 9780735404311 ; , s. 190-204
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Konferensbidrag (refereegranskat)abstract
- The calibration strategy of the GLAST Large Area Telescope (LAT) combines analysis of cosmic ray data with accelerator particle beams measurements. An advanced Monte Carlo simulation of the LAT, based on the Geant4 package, was set up to reproduce the LAT response to such radiation and to benchmark the event reconstruction and the background rejection strategy before launch and during operation. To validate the LAT simulation, a massive campaign of beam tests was performed between July and November 2006, in parallel with the LAT integration and test, on the LAT Calibration Unit. This is a detector built with spare flight modules and flight-like readout electronics, which was exposed to a large variety of beams, representing the whole spectrum of the signal that will be detected by the LAT, using the CERN and the GSI accelerator facilities. Beams of photons (0 - 2.5 GeV), electrons (1-300 GeV), hadrons (π and p, a few GeV - 100 GeV) and ions (C, Xe, 1.5 GeV/n) were shot through the CU to measure the physical processes taking place in the detector and eventually fine-tune their description in the LAT Monte Carlo simulation. This paper describes the motivations and goals of the test runs, the many different experimental setups used, the measured detector performance and preliminary results of the LAT Monte Carlo validation.
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| 2. |
- Bergström, L., et al.
(författare)
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GLAST sensitivity to cosmological dark matter annihilations into γ-rays
- 2007
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Ingår i: First GLAST Symposium. - : American Institute of Physics (AIP). - 9780735404311 ; , s. 504-505
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Konferensbidrag (refereegranskat)abstract
- Pair annihilation of weakly interacting massive particle (WIMP) dark matter into high energy photons taking place in dark matter halos at all redshifts might contribute to the extragalactic diffuse gamma-ray radiation. The γ- annihilation channel would give rise to a distinct feature in the spectrum, a line which is distorted by the integration over all cosmological redshifts. We present a study of GLAST sensitivity to detect an extragalactic signal from a generic, thermal WIMP with a continuous spectrum part, modeled with annihilations into bb̄, and a γ-line, from the 2γ final state.
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| 3. |
- Carlson, Per, et al.
(författare)
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On detecting strange quark matter with GLAST-LAT
- 2007
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Ingår i: First GLAST Symposium. - : AIP. - 9780735404311 ; , s. 518-519
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Konferensbidrag (refereegranskat)abstract
- Strange Quark Matter is a proposed state of hadronic matter consisting of up, down and strange quarks. If this state is stable as proposed by various phenomenological models, there will most likely be an experimentally accessible component of strange quark matter particles (strangelets) in the cosmic ray flux. In GLAST the prime signature would be a A particle produced in hadronic interaction of the strangelet in the tracker, decaying into a proton and pion with relatively large opening angle, In this contribution we discuss the possibility for the GLAST-LAT to measure these events and separate them from background.
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| 4. |
- Conrad, Jan, et al.
(författare)
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Statistical analysis of detection of, and upper limits on, dark matter lines
- 2007
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Ingår i: First GLAST Symposium. - : AIP. - 9780735404311 ; , s. 586-587
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Konferensbidrag (refereegranskat)abstract
- In this note we present calculations of coverage and power for three different methods which could be used to calculate upper limits and/or claim discovery in a GLAST-LAT search fora dark matter line. The methods considered are Profile Likelihood, Bayesian factors and likelihood ratio confidence intervals and the calculations are done considering a simple benchmark model of two uncorrelated Poissonian measurements. Profile likelihood has the best coverage properties, the standard X-2 test the worst. For the power, the situation is vice-versa. In choosing a method one has to consider the false detection rate (1 - coverage) and counterweigh it to the possible achievable power.
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| 5. |
- Edmonds, Y., et al.
(författare)
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Estimate for GLAST LAT milky way Dark Matter WIMP line sensitivity
- 2007
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Ingår i: First GLAST Symposium. - : American Institute of Physics (AIP). - 9780735404311 ; , s. 514-515
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Konferensbidrag (refereegranskat)abstract
- The LAT Dark Matter and New Physics Working group has been developing approaches for the indirect astrophy sical detection of annihilation of dark matter. Our work has assumed that a significant component of dark matter is a new type of Weakly Interacting Massive Particle (WIMP). The annihilation of two WIMPs usually results in the production of many high energy gamma rays (>1 GeV) that can be well measured in the GLAST LAT if present. There is also the possibility to observe γ lines from annihilation into γγ and or γZ final states. In popular SUSY theories these line decays occur at the 10-4 to 10-2 branching fraction level. Estimates of LAT sensitivity (at 5σ above background) and upper limits (upper limit at the 95% confidence level) to these WIMP lines will be presented. These sensitivities are given in photons/cm2/sec/sr and so do not depend on the WIMP models. However, they do depend on the diffuse background model. The latter is derived from GALPROP [1] based on EGRET and other data in the EGRET energy range. We use extrapolations, provided by the GALPROP team to the higher energy range of 150 GeV explored in the preliminary line sensitivity study presented here. Comparison with theory depends upon the WIMP model (e.g., line energy and 1 or 2 lines), the DM halo model, and other astrophysics backgrounds. Thus estimates of the ability of the LAT to actually observe WIMP lines can vary over orders of magnitude depending upon which models are chosen.
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| 6. |
- Karlsson, Niklas, et al.
(författare)
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Simulation of gamma rays from proton interaction in local galaxies
- 2007
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Ingår i: First GLAST Symposium. - : American Institute of Physics (AIP). - 9780735404311 ; , s. 486-487
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Konferensbidrag (refereegranskat)abstract
- The GLAST Large Area Telescope will provide unprecedented opportunities to detect cosmic GeV gamma rays, thanks to its large effective area, field of view and angular resolution compared with earlier telescopes. We present here the possibility of detecting GeV gamma rays produced by interactions of accelerated protons (or hadrons) with surrounding ambient material. Sources where such detection could be made include local galaxies, such as the Large Magellanic Cloud (LMC), molecular clouds and other extended sources. We have calculated the expected gamma-ray spectrum for an isotropic distribution of protons in the LMC and simulated a one-year GLAST-LAT observation.
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