15547042
Searches for Particle Dark Matter with the GLAST Large Area Telescope
The Large Area Telescope (LAT), one of two instruments on the Gamma-ray Large Area Space Telescope (GLAST) mission, scheduled for launch by NASA in 2007, is an imaging, wide field-of-view, high-energy gamma-ray telescope, covering the approximate energy range from 20 MeV to more than 300 GeV. 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.
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.
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.
15563733
Applying rule ensembles to the search for super-symmetry at the large hadron collider
In this note we give an example application of a recently presented predictive learning method called Rule Ensembles. The application we present is the search for super-symmetric particles at the Large Hadron Collider. In particular, we consider the problem of separating the background coming from top quark production from the signal of super-symmetric particles. The method is based on an expansion of base learners, each learner being a rule, i.e. a combination of cuts in the variable space describing signal and background. These rules are generated from an ensemble of decision trees. One of the results of the method is a set of rules (cuts) ordered according to their importance, which gives useful tools for diagnosis of the model. We also compare the method to a number of other multivariate methods, in particular Artificial Neural Networks, the likelihood method and the recently presented boosted decision tree method. We find better performance of Rule Ensembles in all cases. For example for a given significance the amount of data needed to claim SUSY discovery could be reduced by 15% using Rule Ensembles as compared to using a likelihood method.
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.
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.
118777630
A Study of the $Q^{2}$ Dependence of the QCD Coupling Constant from the Transverse Momentum of Jets in Deep Inelastic Muon Scattering
123338648
New Opportunities for Surprise
If history is any guide, then there is a good chance that our present description of neutrinos is wrong. Over the past 30 years, neutrino physics has again and again produced results which took us by surprise, and forced us to change our theoretical direction. In light of this, it is worth examining the experimental clues we now have to see if they lead to ideas outside our "New Standard Model." Our present paradigm says that there are only three neutrinos participating in the weak interaction. They are light, with masses less than 0.1 eV, and predicted to be Majorana neutrinos, that is, each is its own antiparticle. The light mass is motivated by the see-saw model, which postulates partners which are very massive (~hundreds of GeV). By contrast with this "conventional wisdom," this talk discusses five examples of experimental results which, if confirmed, would cause us to rethink our theory. It focuses only on oscillations, and on those questions which can be addressed at accelerators. Other ways neutrinos may be surprising, such as the anomalous measurement of sin2θW from NuTeV, are left for other talks. The ideas discussed here are best explored through accelerator-produced neutrino beams. So the reasons why beam-based experiments are becoming the venue-of-choice are then examined. Lastly, the first two of the five ideas are explored in detail.
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.
15349771
Brane tensions and coupling constants from within M theory
Abstract Reviewing the cancellation of local anomalies of M-theory on R 10 ×S 1 / Z 2 the Yang-Mills coupling constant on the boundaries is rederived. The result is λ 2 =2 1/3 (2 π )(4 πκ 2 ) 2/3 corresponding to η = λ 6 / κ 4 =256 π 5 in the “upstairs” units used by Hořava and Witten and differs from their calculation. It is shown that these values are compatible with the standard membrane and fivebrane tensions derived from the M-theory bulk action. In view of these results it is argued that the natural units for M-theory on R 10 ×S 1 / Z 2 are the “downstairs” units where the brane tensions take their standard form and the Yang-Mills coupling constant is λ 2 =4 π (4 πκ 2 ) 2/3 .
561638
Coherent neutrino scattering in dark matter detectors
Coherent elastic neutrino- and WIMP-nucleus interaction signatures are expected to be quite similar. This paper discusses how a next generation ton-scale dark matter detector could discover neutrino-nucleus coherent scattering, a precisely-predicted Standard Model process. A high intensity pion- and muon- decay-at-rest neutrino source recently proposed for oscillation physics at underground laboratories would provide the neutrinos for these measurements. In this paper, we calculate raw rates for various target materials commonly used in dark matter detectors and show that discovery of this interaction is possible with a 2 ton$\cdot$year GEODM exposure in an optimistic energy threshold and efficiency scenario. We also study the effects of the neutrino source on WIMP sensitivity and discuss the modulated neutrino signal as a sensitivity/consistency check between different dark matter experiments at DUSEL. Furthermore, we consider the possibility of coherent neutrino physics with a GEODM module placed within tens of meters of the neutrino source.