83 research outputs found
Modern Statistical Methods for GLAST Event Analysis
We describe a statistical reconstruction methodology for the GLAST LAT. The
methodology incorporates in detail the statistics of the interactions of
photons and charged particles with the tungsten layers in the LAT, and uses the
scattering distributions to compute the full probability distribution over the
energy and direction of the incident photons. It uses model selection methods
to estimate the probabilities of the possible geometrical configurations of the
particles produced in the detector, and numerical marginalization over the
energy loss and scattering angles at each layer. Preliminary results show that
it can improve on the tracker-only energy estimates for muons and electrons
incident on the LAT.Comment: To appear in the proceedings of the First GLAST Symposium (held at
Stanford University, 5-8 February 2007
WIMP searches with gamma rays in the Fermi era: challenges, methods and results
The launch of the gamma-ray telescope Fermi Large Area Telescope (Fermi-LAT)
started a pivotal period in indirect detection of dark matter. By outperforming
expectations, for the first time a robust and stringent test of the paradigm of
weakly interacting massive particles (WIMPs) is within reach. In this paper, we
discuss astrophysical targets for WIMP detection and the challenges they
present, review the analysis tools which have been employed to tackle these
challenges, and summarize the status of constraints on and the claimed
detections in the WIMP parameter space. Methods and results will be discussed
in comparison to Imaging Air Cherenkov Telescopes. We also provide an outlook
on short term and longer term developments.Comment: 72 pages, 7 figures, Invited review for Journal of Experimental and
Theoretical Physics,v3: added a few references, addressed referee comment
Studies of Cosmic Rays with GeV Gamma Rays
We describe the role of GeV gamma-ray observations with GLAST-LAT (Gamma-ray
Large Area Space Telescope - Large Area Telescope) in identifying interaction
sites of cosmic-ray proton (or hadrons) with interstellar medium (ISM). We
expect to detect gamma rays from neutral pion decays in high-density ISM
regions in the Galaxy, Large Magellanic Cloud, and other satellite galaxies.
These gamma-ray sources have been detected already with EGRET (Energetic Gamma
Ray Experiment Telescope) as extended sources (eg. LMC and Orion clouds) and
GLAST-LAT will detect many more with a higher spatial resolution and in a wider
spectral range. We have developed a novel image restoration technique based on
the Richardson-Lucy algorithm optimized for GLAST-LAT observation of extended
sources. Our algorithm calculates PSF (point spread function) for each event.
This step is very important for GLAST-LAT and EGRET image analysis since PSF
varies more than one order of magnitude from one gamma ray to another depending
on its energy as well as its impact point and angle in the instrument. The
GLAST-LAT and EGRET image analysis has to cope with Poisson fluctuation due to
low number of detected photons for most sources. Our technique incorporates
wavelet filtering to minimize effects due to the fluctuation. Preliminary
studies on some EGRET sources are presented, which shows potential of this
novel image restoration technique for the identification and characterisation
of extended gamma-ray sources.Comment: 9 pages, 6 figures, Invited Talk at International Workshop on
"Cosmic-Rays and High Energy Universe," Aoyama-Gakuin University, Shibuya,
Tokyo, Japan, March 5-6, 200
Studies of EGRET sources with a novel image restoration technique
We have developed an image restoration technique based on the Richardson-Lucy
algorithm optimized for GLAST-LAT image analysis. Our algorithm is original
since it utilizes the PSF (point spread function) that is calculated for each
event. This is critical for EGRET and GLAST-LAT image analysis since the PSF
depends on the energy and angle of incident gamma-rays and varies by more than
one order of magnitude. EGRET and GLAST-LAT image analysis also faces Poisson
noise due to low photon statistics. Our technique incorporates wavelet
filtering to minimize noise effects. We present studies of EGRET sources using
this novel image restoration technique for possible identification of extended
gamma-ray sources.Comment: 5 pages, 3 figures. Presented at First GLAST Symposium, Stanford
University, Stanford, CA, USA, February 5-8, 200
Utilisation des infrastructures de la Grille EGI pour les simulations de CTA
Utilisation des infrastructures de la Grille EGI pour les simulations de CT
Recommended from our members
A Parameterization Invariant Approach to the Statistical Estimation of the CKM Phase alpha
In contrast to previous analyses, we demonstrate a Bayesian approach to the estimation of the CKM phase {alpha} that is invariant to parameterization. We also show that in addition to computing the marginal posterior in a Bayesian manner, the distribution must also be interpreted from a subjective Bayesian viewpoint. Doing so gives a very natural interpretation to the distribution. We also comment on the effect of removing information about {beta}{sup 00}
DIRAC framework evaluation for the -LAT and CTA experiments
DIRAC (Distributed Infrastructure with Remote Agent Control) is a general
framework for the management of tasks over distributed heterogeneous computing
environments. It has been originally developed to support the production
activities of the LHCb (Large Hadron Collider Beauty) experiment and today is
extensively used by several particle physics and biology communities. Current
( Large Area Telescope -- LAT) and planned (Cherenkov Telescope Array --
CTA) new generation astrophysical/cosmological experiments, with very large
processing and storage needs, are currently investigating the usability of
DIRAC in this context. Each of these use cases has some peculiarities:
-LAT will interface DIRAC to its own workflow system to allow the access
to the grid resources, while CTA is using DIRAC as workflow management system
for Monte Carlo production and analysis on the grid. We describe the prototype
effort that we lead toward deploying a DIRAC solution for some aspects of
-LAT and CTA needs.Comment: proceedings to CHEP 2013 conference : http://www.chep2013.org
A Parameterization Invariant Approach to the Statistical Estimation of the CKM Phase
In contrast to previous analyses, we demonstrate a Bayesian approach to the
estimation of the CKM phase that is invariant to parameterization. We
also show that in addition to {\em computing} the marginal posterior in a
Bayesian manner, the distribution must also be {\em interpreted} from a
subjective Bayesian viewpoint. Doing so gives a very natural interpretation to
the distribution. We also comment on the effect of removing information about
.Comment: 14 pages, 3 figures, 1 table, minor revision; to appear in JHE
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