54222702
Implications for constrained supersymmetry of combined H.E.S.S. observations of dwarf galaxies, the Galactic halo and the Galactic Centre
In order to place limits on dark matter (DM) properties using gamma-ray observations, previous analyses have often assumed a very simple parametrisation of the gamma-ray annihilation yield; typical ...
117090989
Statistical analysis of detection of, and upper limits on, dark matter lines
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 for a 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 χ2 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.
118846253
Future dark matter searches with the GLAST-LAT
The Large Area Telescope, one of two instruments on the Gamma-ray Large Area Space Telescope mission, scheduled for launch by NASA in early 2008, is a high-energy gamma-ray telescope, sensitive to an energy range from approximately 20 MeV to more than 300 GeV and exceeding the sensitivity of its predecessor EGRET by nearly two orders of magnitude. Annihilation of Weakly Interacting Massive Particles (WIMP), predicted in many extensions of the Standard Model of Particle Physics, may give rise to a signal in gamma-ray spectra from many cosmic sources. In this contribution we give an overview of the searches for WIMP Dark Matter performed by the GLAST-LAT collaboration, in particular we discuss the sensitivity of GLAST to thermal WIMP dark matter in the galactic center and to high energy (50 -150 GeV) gamma-ray lines resulting from WIMP pair annihilation into two gamma-rays.
15402465
Coverage of Confidence Intervals for Poisson Statistics in Presence of Systematic Uncertainties
Coverage of Confidence Intervals for Poisson Statistics in Presence of Systematic Uncertainties
120082547
Fermi Gamma-ray Space Telescope sees first light
With exceptional resolution and sensitivity, the latest orbiting gamma-ray telescope based on detection techniques from particle physics is opening a new window on the high-energy universe.
18437847
Fluctuation studies and energy reconstruction in a segmented calorimeter
In order to better understand energy estimation of electromagnetic showers in segmented calorimeters, detailed Geant4 simulation studies of electromagnetic showers in the energy range 1-100 GeV in CsI have been performed. When sampled in layers of 1.99 cm thickness, corresponding to 1.08 radiation lengths, the energy fluctuations in the samples show distributions that vary significantly with depth. The energy distributions are similar for incident electrons and photons and were found to change systematically along the shower, varying little with the initial energy. Three probability distributions have been fitted to the data: negative binomial, log-normal and Gaussian distributions, none of which gives a good fit over the full shower length. The obtained parameterizations might be useful in the use of the maximum likelihood method for estimating the energy. Two methods for estimating the energy have also been studied. One method is based on fitting individual longitudinal shower profiles with a Gamma-function, the other one corrects the measured energy for leakage by utilizing the energy deposited in the last layer. Our simulations indicate that the last-layer correction method applied to photons and electrons of 1 and 10 GeV gives about a factor of 2 improvement in the energy resolution.
15447302
A measurement of the absorption of liquid argon scintillation light by dissolved nitrogen at the part-per-million level
We correct a mistake in the calculation of the molecular absorption cross section of nitrogen, and a minor plot labelling mistake, which were found after publication of this paper.
2261610
Atmospheric tau neutrinos in a multikiloton liquid argon detector
An ultralarge liquid argon time projection chamber based neutrino detector will have the uncommon ability to detect atmospheric {nu}{sub {tau}}/{nu}{tau} events. This paper discusses the most promising modes for identifying charged current {nu}{sub {tau}}/{nu}{tau}, and shows that, with simple kinematic cuts, {approx}30 {nu}{sub {tau}}+{nu}{tau} interactions can be isolated in a 100 kt{center_dot}yr exposure, with greater than 4{sigma} significance. This sample is sufficient to perform flux-averaged total cross-section and cross-section shape parametrization measurements--the first steps toward using {nu}{sub {tau}}/{nu}{tau} to search for physics beyond the standard model.
118385577
Measurements of the rates of forward jet production in deep inelastic muon scattering
20950520
Photodegradation mechanisms of tetraphenyl butadiene coatings for liquid argon detectors
We report on studies of degradation mechanisms of tetraphenyl butadiene (TPB) coatings of the type used in neutrino and dark matter liquid argon experiments. Using gas chromatography coupled to mass spectrometry we have detected the ultraviolet-blocking impurity benzophenone. We monitored the drop in performance and increase of benzophenone concentration in TPB plates with exposure to ultraviolet (UV) light, and demonstrate the correlation between these two variables. Based on the presence and initially exponential increase in the concentration of benzophenone observed, we propose that TPB degradation is a free radical-mediated photooxidation reaction, which is subsequently confirmed by displaying delayed degradation using a free radical inhibitor. Finally we show that the performance of wavelength-shifting coatings of the type envisioned for the LBNE experiment can be improved by 10-20%, with significantly delayed UV degradation, by using a 20% admixture of 4-tert-Butylcatechol.
16058464
Testing of cryogenic photomultiplier tubes for the MicroBooNE experiment
The MicroBooNE detector, to be located on axis in the Booster Neutrino Beamline (BNB) at the Fermi National Accelerator Laboratory (Fermilab), consists of two main components: a large liquid argon time projection chamber (LArTPC), and a light collection system. Thirty-two 8-inch diameter Hamamatsu R5912-02mod cryogenic photomultiplier tubes (PMTs) will detect the scintillation light generated in the liquid argon (LAr). This article first describes the MicroBooNE PMT performance test procedures, including how the light collection system functions in the detector, and the design of the PMT base. The design of the cryogenic test stand is then discussed, and finally the results of the cryogenic tests are reported.