6,227 research outputs found
Status Report of the CAST Experiment
The CAST Collaboration has recently published the best experimental limit on the axion-photon coupling dominating for masses up to 0.02 eV. This limit superseding for the first time the astrophysical limits. Preliminary results from the He-4 Phase are presented, extending to masses up to 0.39 eV. The collaboration has succesfully commissioned the He-3 gas system which is indispensable to reach masses up to 1.2 eV, covering the HDM limit. During 2007 the CCD detector and the X-ray telescope were refurbished and all the other magnet lines were equipped with better performing Micromegas detectors. The experiment has already started the He-3 run based on solid grounds for further exploring uncharted but promising regions of phase space
CAST results and Axion review
We present results from the CERN Axion Solar Telescope (CAST) and the Axion
Dark Matter eXperiment (ADMX), together with a brief review on prospects on
Axion searches with a variety of experimental techniques. CAST has explored
masses up to 0.64 eV setting the most stringent limit on the axion-photon
coupling, apart for the micro-eV region where ADMX is the most competitive
experiment. CAST is aiming at surpassing the 1eV WMAP upper limit and possibly
revisiting the operation in vacuum with extra sensitive X-ray detectors, while
ADMX, using improved extra sensitive SQUID amplifiers will explore the micro-eV
mass range.Comment: 8 pages, 4 figures, XLIVth Rencontres de Moriond EW 2009 proceeding
Performance of the Micromegas detector in the CAST experiment
The gaseous Micromegas detector designed for the CERN Axion search experiment
CAST, operated smoothly during Phase-I, which included the 2003 and 2004
running periods. It exhibited linear response in the energy range of interest
(1-10keV), good spatial sensitivity and energy resolution (15-19% FWHM at
5.9keV)as well as remarkable stability. The detector's upgrade for the 2004
run, supported by the development of advanced offline analysis tools, improved
the background rejection capability, leading to an average rate 5x10^-5
counts/sec/cm^2/keV with 94% cut efficiency. Also, the origin of the detected
background was studied with a Monte Carlo simulation, using the GEANT4 package.Comment: Prepared for PSD7: The Seventh International Conference on Position
Sensitive Detectors, Liverpool, United Kingdom, 12-16 Sep. 200
Seen and unseen tidal caustics in the Andromeda galaxy
Indirect detection of high-energy particles from dark matter interactions is
a promising avenue for learning more about dark matter, but is hampered by the
frequent coincidence of high-energy astrophysical sources of such particles
with putative high-density regions of dark matter. We calculate the boost
factor and gamma-ray flux from dark matter associated with two shell-like
caustics of luminous tidal debris recently discovered around the Andromeda
galaxy, under the assumption that dark matter is its own supersymmetric
antiparticle. These shell features could be a good candidate for indirect
detection of dark matter via gamma rays because they are located far from the
primary confusion sources at the galaxy's center, and because the shapes of the
shells indicate that most of the mass has piled up near apocenter. Using a
numerical estimator specifically calibrated to estimate densities in N-body
representations with sharp features and a previously determined N-body model of
the shells, we find that the largest boost factors do occur in the shells but
are only a few percent. We also find that the gamma-ray flux is an order of
magnitude too low to be detected with Fermi for likely dark matter parameters,
and about 2 orders of magnitude less than the signal that would have come from
the dwarf galaxy that produces the shells in the N-body model. We further show
that the radial density profiles and relative radial spacing of the shells, in
either dark or luminous matter, is relatively insensitive to the details of the
potential of the host galaxy but depends in a predictable way on the velocity
dispersion of the progenitor galaxy.Comment: ApJ accepte
The Micromegas detector of the CAST experiment
A low background Micromegas detector has been operating in the CAST
experiment at CERN for the search of solar axions during the first phase of the
experiment (2002-2004). The detector, made out of low radioactivity materials,
operated efficiently and achieved a very low level of background rejection (5 x
10^-5 counts/keV/cm^2/s) without shielding.Comment: 13 pages, 12 figures and images, submitted to New Journal o
Performances of Anode-resistive Micromegas for HL-LHC
Micromegas technology is a promising candidate to replace Atlas forward muon
chambers -tracking and trigger- for future HL-LHC upgrade of the experiment.
The increase on background and pile-up event probability requires detector
performances which are currently under studies in intensive RD activities.
We studied performances of four different resistive Micromegas detectors with
different read-out strip pitches. These chambers were tested using \sim120 GeV
momentum pions, at H6 CERN-SPS beam line in autumn 2010. For a strip pitch 500
micrometers we measure a resolution of \sim90 micrometers and a efficiency of
~98%. The track angle effect on the efficiency was also studied. Our results
show that resistive techniques induce no degradation on the efficiency or
resolution, with respect to the standard Micromegas. In some configuration the
resistive coating is able to reduce the discharge currents at least by a factor
of 100.Micromegas technology is a promising candidate to replace Atlas forward
muon chambers -tracking and trigger- for future HL-LHC upgrade of the
experiment. The increase on background and pile-up event probability requires
detector performances which are currently under studies in intensive RD
activities. We studied performances of four different resistive Micromegas
detectors with different read-out strip pitches. These chambers were tested
using \sim120 GeV momentum pions, at H6 CERN-SPS beam line in autumn 2010. For
a strip pitch 500 micrometers we measure a resolution of \sim90 micrometers and
a efficiency of \sim98%. The track angle effect on the efficiency was also
studied. Our results show that resistive techniques induce no degradation on
the efficiency or resolution, with respect to the standard Micromegas. In some
configuration the resistive coating is able to reduce the discharge currents at
least by a factor of 100.Comment: "Presented at the 2011 Hadron Collider Physics symposium (HCP-2011),
Paris, France, November 14-18 2011, 3 pages, 6 figures.
CAST microbulk micromegas in the Canfranc Underground Laboratory
During the last taking data campaigns of the CAST experiment, the micromegas
detectors have achieved background levels of keVcms between 2 and 9 keV. This performance has
been possible thanks to the introduction of the microbulk technology, the
implementation of a shielding and the development of discrimination algorithms.
It has motivated new studies towards a deeper understanding of CAST detectors
background. One of the working lines includes the construction of a replica of
the set-up used in CAST by micromegas detectors and its installation in the
Canfranc Underground Laboratory. Thanks to the comparison between the
performance of the detectors underground and at surface, shielding upgrades,
etc, different contributions to the detectors background have been evaluated.
In particular, an upper limit keVcms
for the intrinsic background of the detector has been obtained. This work means
a first evaluation of the potential of the newest micromegas technology in an
underground laboratory, the most suitable environment for Rare Event Searches.Comment: 6 pages, 8 figures. To appear in the proceedings of the 2nd
International Conference on Technology and Instrumentation for Particle
Physics (TIPP 2011
A low background Micromegas detector for the CAST experiment
A low background Micromegas detector has been operating on the CAST
experiment at CERN for the search of solar axions during the first phase of the
experiment (2002-2004). The detector operated efficiently and achieved a very
low level of background rejection ( counts
keVcms) thanks to its good spatial and energy resolution
as well as the low radioactivity materials used in the construction of the
detector. For the second phase of the experiment (2005-2007), the detector will
be upgraded by adding a shielding and including focusing optics. These
improvements should allow for a background rejection better than two orders of
magnitude.Comment: 6 pages, 3 figures To appear on the proceedings of the 9th ICATPP
Conference on AStroparticle, Particle, Space Physics, Detectors and Medical
Physics Application
Progress on a spherical TPC for low energy neutrino detection
The new concept of the spherical TPC aims at relatively large target masses
with low threshold and background, keeping an extremely simple and robust
operation. Such a device would open the way to detect the neutrino-nucleus
interaction, which, although a standard process, remains undetected due to the
low energy of the neutrino-induced nuclear recoils. The progress in the
development of the fist 1 m prototype at Saclay is presented. Other physics
goals of such a device could include supernova detection, low energy neutrino
oscillations and study of non-standard properties of the neutrino, among
others.Comment: 3 pages, talk given at the 9th Workshop on Topics in Astroparticle
and Underground Physics, Zaragoza, September 10-1
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