118222129
Final Report of the Simulation Optimization Task Force
This is the final report of the ATLAS Simulation Optimization Task Force, establishedin June of 2007. This note justifies the selected Geant4 version, physics list, and range cuts to be used by the default ATLAS simulation for initial data taking and beyond. The current status of several projects, including detector description, simulation validation, studies of additional Geant4 parameters, and cavern background, are reported.
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Tagging of low-pt electrons from b decays with the ATLAS electromagnetic calorimeter
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Status of the ATLAS calorimetry simulation for the TP in DICE
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ATLAS status and highlights
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Impact of energy and luminosity upgrades at LHC on the physics programme of ATLAS
The impact of possible LHC upgrades on the physics capabilities of the ATLAS detector is discussed. As a benchmark, an increase in the luminosity by a factor of 10 is considered. For comparison, the doubling of the LHC energy is also explored. Both upgrades significantly enhance the physics capabilities of ATLAS. Measured in terms of the mass reach for new particles, the energy upgrade is more powerful. However, in cases where the effect of an upgrade is to increase the precision of measurements as a result of larger data samples, the luminosity upgrade can be at least as powerful. The pile-up of minimum bias events at higher luminosity could limit the physics performance of ATLAS in areas where tagging of forward jets is needed.
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Physics in ATLAS at a possible upgraded LHC
The impact on the physics capabilities of the ATLAS detector of possible LHC upgrades is discussed. A doubling of the LHC energy or an increase in the luminosity by a factor of ten are considered. Both upgrades significantly enhance the physics capabilities of ATLAS. In general, the energy upgrade is more powerful since the pile-up of minimum bias events at higher luminosity impacts the physics performance of ATLAS in some areas.
118532651
AGILE Observations of Terrestrial Gamma-Ray Flashes
The AGILE satellite, operating since mid 2007 and primarily devoted to high-energy astrophysics,is one of the only three currently operating space instruments capable of detecting TerrestrialGamma-Ray Flashes (TGFs), together with RHESSI and Fermi-GBM. Thanks to the AGILEMini-Calorimeter instrument energy range extended up to 100MeV and its ﬂexible trigger logic onsub-millisecond time scales, AGILE is detecting more than 10 TGFs/month, adding a wealth ofobservations which pose severe constrains on production models. The main AGILE discoveries inTGF science during two and a half years of observations are the following: 1) the TGF spectrumextends well above 40 MeV, 2) the high energy tail of the TGF spectrum is harder than expectedand cannot be easily explained by previous theoretical models, 3) TGFs can be localized from spaceusing high-energy photons detected by the AGILE gamma-ray imaging detector. In this presenta-tion we will describe the characteristics of the 2.5-years AGILE TGF sample, focusing on the recentresults concerning the TGF high-energy spectral characteristics.I. INTRODUCTION
119196535
Evaluating the maximum likelihood method for detecting short-term variability of AGILE γ-ray sources
Context. The AGILE space mission (whose instrument is sensitive to the energy ranges 18–60 keV, and 30 MeV–50 GeV) has been operating since 2007. Assessing the statistical significance of the time variability of γ-ray sources above 100 MeV is a primary task of the AGILE data analysis. In particular, it is important to verify the instrument sensitivity in terms of Poisson modeling of the data background, and to determine the post-trial confidence of detections. Aims. The goals of this work are: (i) to evaluate the distributions of the likelihood ratio test for both “empty” fields and regions of the Galactic plane, and (ii) to calculate the probability of false detections over multiple time intervals. Methods. We describe in detail the techniques used to search for short-term variability in the AGILE γ-ray source database. We describe the binned maximum likelihood method used for the analysis of AGILE data, and the numerical simulations that support the characterization of the statistical analysis. We apply our method to both Galactic and extragalactic transients, and provide a few examples. Results. After checking the reliability of the statistical description tested with the real AGILE data, we obtain the distribution of p-values for blind and specific source searches. We apply our results to the determination of the post-trial statistical significance of detections of transient γ-ray sources in terms of pre-trial values. Conclusions. The results of our analysis allow a precise determination of the post-trial significance of γ-ray sources detected by AGILE.
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The mini-calorimeter for the AGILE satellite
AGILE is a small space mission of the Italian Space Agency (ASI) devoted to observations for astrophysics in the gamma-ray energy range 30 MeV-50 GeV with a simultaneous window in the X-ray band 10 keV-40 keV. AGILE payload is made of a tungsten-silicon tracker, a CsI mini-calorimeter for the high energy band and a silicon based X-ray detector (SuperAgile); an anticoincidence system carries out background rejection. In the gamma-ray's band the satellite will have a field of view of about 1/5 of the sky, with angular resolution of a few arc-minutes and good timing resolution. For the high energy AGILE detection principle is based on the pair production process that arises from the interaction between photons and the tungsten layers above the silicon tracker. The silicon tracker is designed to determine the direction of the incoming radiation, while the mini-calorimeter evaluates the energy of the interacting photons and particles. For the detection of transients and gamma-ray burst events, the mini-calorimeter will also work as a stand-alone gamma-ray detector, with no imaging capabilities, covering the energy range 250 keV-250 MeV. The mini-calorimeter is made of an array of position sensitive CsI(Tl) scintillator bars with photodiode read-out. The characteristics of its detector elements and the front end electronics signal processing allow a moderate position reconstruction of the detected event. In this paper a description of the mini-calorimeter is reported as well as a summary of performances reached with the pre-flight instrument models already built and tested.
121426765
The mini-calorimeter detector for the AGILE mission
AGILE is an ASI space mission for high energy astrophysics in the gamma ray energy range 30MeV-50GeV, and in the X-ray band (10keV-40keV). AGILE is composed of three detecting systems: a Tungsten-Silicon Tracker, a Csl Mini-Calorimeter and a Silicon based X-ray detector (Super-Agile), plus an anticoincidence system for background rejection. The satellite will have good imaging performances (with angular resolution of a few arc-minutes in the gamma ray band), good timing resolution and a large field of view (about 1/5 of the sky). AGILE high energy detector is composed of a Silicon Tracker, a Mini-Calorimeter, the Anticoincidence and the Data Handling system The Mini-Calorimeter can also work as a stand-alone gamma ray detector in the energy range 250keV-250MeV, with no imaging capabilities, for the detection of transients and gamma ray burst events and for the evaluation of gamma ray background fluctuations. The Mini-Calorimeter is made of 30 independent elements of 37.5 × 2.3 × 1.5  cm stacked in two layers. Each detector scintillator signal is read out via two photodiodes glued on the small surfaces of the bar. The characteristics of the engineering model detectors has been deeply investigated and will be reported.
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Test campaign of the mini-calorimeter for the AGILE satellite
The AGILE Mini-Calorimeter (MCAL, with total on-axis radiation length 1.5 X0) comprises 2 orthogonal planes each consisting of 16 CsI(Tl) bars. Its primary purpose is the energy determination of gamma-rays detected by the Gamma-Ray Imaging Detector (GRID) Tracker (energy range 30 MeV–50 GeV). In addition, the MCAL is capable of independently triggering and detecting gamma-ray bursts and other impulsive events in the energy range 0.25–250 MeV. A MCAL prototype, comprising 8 CsI(Tl) detector elements, was tested both with laboratory sources and with charged particles (p=1 GeV/c) during an AGILE Beam Test carried out in November 2000 at the CERN T11 beamline (East Hall, CERN PS). The test setup included a prototype of the electronic chain. A prototype of the digital data acquisition chain, which will be the baseline of the payload Electronic Ground Support Equipment, was also built and tested. We present the preliminary results of this test campaign dedicated to characterizing the detector unit and electronics.