15358736
Search for neutrino-induced cascades with the AMANDA detector
J. Ahrens, X. Bai, G. Barouch, S.W. Barwick, R.C. Bay, T. Becka, K.-H. Becker, D. Bertrand, F. Binon, A. Biron, S. Böser, J. Booth, O. Botner, A. Bouchta, a O. Bouhali, M.M. Boyce, T. Burgess, S. Carius, A. Chen, D. Chirkin, J. Conrad, J. Cooley, C.G.S. Costa, D.F. Cowen, A. Davour, C. De Clercq, T. DeYoung, b P. Desiati, J.-P. Dewulf, P. Doksus, P. Ekström, T. Feser, J.-M. Frère, T.K. Gaisser, M. Gaug, A. Goldschmidt, A. Hallgren, F. Halzen, K. Hanson, R. Hardtke, T. Hauschildt, M. Hellwig, G.C. Hill, P.O. Hulth, K. Hultqvist, S. Hundertmark, J. Jacobsen, A. Karle, J. Kim, B. Koci, L. Köpke, M. Kowalski, J.I. Lamoureux, H. Leich, M. Leuthold, P. Lindahl, I. Liubarsky, D.M. Lowder, c J. Madsen, P. Marciniewski, H.S. Matis, C.P. McParland, T.C. Miller, d Y. Minaeva, P. Miočinović, P.C. Mock, e R. Morse, T. Neunhöffer, P. Niessen, D.R. Nygren, H. Ogelman, Ph. Olbrechts, C. Pérez de los Heros, A.C. Pohl, R. Porrata, f P.B. Price, G.T. Przybylski, K. Rawlins, C. Reed, g E. Resconi, W. Rhode, M. Ribordy, S. Richter, J. Rodŕıguez Martino, P. Romenesko, D. Ross, H.-G. Sander, T. Schmidt, D. Schneider, R. Schwarz, A. Silvestri, M. Solarz, G.M. Spiczak, C. Spiering, N. Starinsky, h D. Steele, P. Steffen, R.G. Stokstad, K.-H. Sulanke, I. Taboada, i L. Thollander, S. Tilav, M. Vander Donckt, C. Walck, C. Weinheimer, C.H. Wiebusch, a C. Widemann, R. Wischnewski, H. Wissing, K. Woschnagg, W. Wu, G. Yodh, and S. Young
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.
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.
118516643
Anisotropies in the diffuse gamma-ray background from dark matter with Fermi LAT: a closer look
This thesis addresses the isotropic diffuse gamma-ray background, as measured by the Fermi gamma ray space telescope, and its implications for indirect detection of dark matter. We describe the measurement of the isotropic background, including also an alternative analysis method besides the one published by the Fermi-LAT collaboration. The measured isotropic diffuse background is compatible with a power law differential energy spectrum with a spectral index of -2.41 ± 0.05 and -2.39 ± 0.08, for the two analysis methods respectively. This is a softer spectrum than previously reported by the EGRET experiment. This rules out any dominant contribution with a significantly different shape, e.g. from dark matter, in the energy range 20 MeV to 102.4 GeV. Instead we present upper limits on a signal originating from annihilating dark matter of extragalactic origin. The uncertainty in the dark matter signal is primarily dependent on the cosmological evolution of the dark matter distribution. We use recent N-body simulations of structure formation, as well as a semi-analytical calculation, to assess this uncertainty. We investigate three main annihilation channels and find that in some, but not in all, of our scenarios we can start to probe, and sometimes rule out, interesting parameter spaces of particle physics models beyond the standard model.We also investigate the possibility to use the angular anisotropies of the annihilation signal to separate it from a background originating from conventional sources, e.g. from active galactic nuclei. By carefully modelling the performance of the Fermi gamma-ray space telescope and galactic foregrounds we find that this method could be as sensitive as using information from the energy spectrum only.
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
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.
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.
54840036
Demonstration of a Lightguide Detector for Liquid Argon TPCs
We report demonstration of light detection in liquid argon using an acrylic lightguide detector system. This opens the opportunity for development of an inexpensive, large-area light collection system for large liquid argon time projection chambers. The guides are constructed of acrylic, with TPB embedded in a surface coating with a matching index of refraction. We study the response to early scintillation light produced by a 5.3 MeV . We measure coating responses from 7 to 8 PE on average, compared to an ideal expectation of 10 PE on average. We estimate the attenuation length of light along the lightguide bar to be greater than 0.5 m. The coating response and the attenuation length can be improved; we show, however, that these results are already sucient for triggering in a large detector.
118381753
A Study of the Fluorescence Response of Tetraphenyl-butadiene
Tetraphenyl-butadiene (TPB) is a widely used fluorescent wavelength-shifter. A common application is in liquid-argon-based particle detectors, where scintillation light is produced in the UV at 128 nm. In liquid argon experiments, TPB is often employed to shift the scintillation light to the visible range in order to allow detection via standard photomultiplier tubes. This paper presents studies on the stability of TPB with time under exposure to light. We also examine batch-to-batch variations. We compare scintillation-grade TPB to 99% pure TPB response. In the 99% pure samples, we report a yellowing effect, and full degradation of the TPB emission-peak, upon extended exposure to light.
119757503
A review of experimental results on neutrino oscillations
122729879
Bringing the SciBar detector to the booster neutrino beam
This document presents the physics case for bringing SciBar, the fully active, finely segmented tracking detector at KEK, to the FNAL Booster Neutrino Beam (BNB) line. This unique opportunity arose with the termination of K2K beam operations in 2005. At that time, the SciBar detector became available for use in other neutrino beam lines, including the BNB, which has been providing neutrinos to the MiniBooNE experiment since late 2002. The physics that can be done with SciBar/BNB can be put into three categories, each involving several measurements. First are neutrino cross section measurements which are interesting in their own right, including analyses of multi-particle final states, with unprecedented statistics. Second are measurements of processes that represent the signal and primary background channels for the upcoming T2K experiment. Third are measurements which improve existing or planned MiniBooNE analyses and the understanding of the BNB, both in neutrino and antineutrino mode. For each of these proposed measurements, the SciBar/BNB combination presents a unique opportunity or will significantly improve upon current or near-future experiments for several reasons. First, the fine granularity of SciBar allows detailed reconstruction of final states not possible with the MiniBooNE detector. Additionally, the BNB neutrino energy spectrum is amore » close match to the expected T2K energy spectrum in a region where cross sections are expected to vary dramatically with energy. As a result, the SciBar/BNB combination will provide cross-section measurements in an energy range complementary to MINERvA and complete the knowledge of neutrino cross sections over the entire energy range of interest to the upcoming off-axis experiments.« less