195 research outputs found
First results from dark matter search experiment with LiF bolometer at Kamioka Underground Laboratory
Tokyo group has performed first underground dark matter search experiment in
2001 through 2002 at Kamioka Observatory(2700m.w.e). The detector is eight LiF
bolometers with total mass 168g aiming for the direct detection of WIMPs via
spin-dependent interaction. With a total exposure of 4.1 kg days, we derived
the limits in the a_p-a_n (WIMP-nucleon couplings) plane and excluded a large
part of the parameter space allowed by the UKDMC experiment.Comment: 15 pages, 5 figure
First Results from Dark Matter Search Experiment in the Nokogiriyama Underground Cell
An experiment to search for hypothetical particle dark matter using cryogenic
thermal detector, or bolometer is ongoing. The bolometer consists of eight
pieces of 21 g LiF absorbers and sensitive NTD germanium thermistors attached
to them and is installed in the Nokogiriyama underground cell which is a
shallow depth site ( m w.e.). We report on the results from the first
running for about ten days using this arrayed bolometer system together with
appropriate shieldings and muon veto counters. From the obtained energy spectra
the exclusion limits for the cross section of the elastic neutralino-proton
scattering are derived under commonly accepted astrophysical assumptions. The
sensitivity for the light neutralino with a mass below 5 GeV is improved by
this work.Comment: 8 pages, Revtex, 4 figure
Limits on the WIMP-Nucleon Coupling Coefficients from Dark Matter Search Experiment with NaF Bolometer
We have performed the underground dark matter search experiment with a sodium
fl uoride (NaF) bolometer array from 2002 through 2003 at Kamioka Observatory
(2700 m.w.e.). The bolometer array consists of eight NaF absorbers with a total
mass of 176 g, and sensitive NTD germanium thermistors glued to each of them.
This experiment aims for the direct detection of weakly interacting massive
part icles (WIMPs) via spin-dependent interaction. With an exposure of 3.38 kg
days, we derived the limits on the WIMP-n ucleon coupling coefficients, a_p and
a_n. These limits confirmed and tightened those derived from our previous
results wit h the lithium fluoride (LiF) bolometer. Our results excluded the
parameter space complementary to the results obtained b y NaI detectors of
UKDMC experiment.Comment: 10 pages, 4 figure
Design and test of an extremely high resolution Timing Counter for the MEG II experiment: preliminary results
The design and tests of Timing Counter elements for the upgrade of the MEG
experiment, MEG II,is presented. The detector is based on several small plates
of scintillator with a Silicon PhotoMultipliers dual-side readout. The
optimisation of the single counter elements (SiPMs, scintillators, geometry) is
described. Moreover, the results obtained with a first prototype tested at the
Beam Test Facility (BTF) of the INFN Laboratori Nazionali di Frascati (LNF) are
presented.Comment: 10 pages, 7 figures. Presented at the 13th Topical Seminar on
Innovative Particle and Radiation Detectors (IPRD13) 7-10 October 2013 Siena,
Ital
WIMP direct detection overview
This review on weakly interacting massive particle (WIMP) dark matter direct
detection focuses on experimental approaches and the corresponding physics
basics. The presentation is intended to provide a quick and concise
introduction for non-specialists to this fast evolving topic of astroparticle
physics.Comment: 13 pages, 6 figures, invited review for the Proc. XXth Int. Conf.
Neutrino Physics and Astrophysics, May 25-30, 2002, Munich, Germany; version
includes correction of typo in eqn.2; to appear in Nucl. Phys. B Proc. Supp
New constraint on the existence of the mu+-> e+ gamma decay
The analysis of a combined data set, totaling 3.6 \times 10^14 stopped muons
on target, in the search for the lepton flavour violating decay mu^+ -> e^+
gamma is presented. The data collected by the MEG experiment at the Paul
Scherrer Institut show no excess of events compared to background expectations
and yield a new upper limit on the branching ratio of this decay of 5.7 \times
10^-13 (90% confidence level). This represents a four times more stringent
limit than the previous world best limit set by MEG.Comment: 5 pages, 3 figures, a version accepted in Phys. Rev. Let
The MEG detector for decay search
The MEG (Mu to Electron Gamma) experiment has been running at the Paul
Scherrer Institut (PSI), Switzerland since 2008 to search for the decay \meg\
by using one of the most intense continuous beams in the world. This
paper presents the MEG components: the positron spectrometer, including a thin
target, a superconducting magnet, a set of drift chambers for measuring the
muon decay vertex and the positron momentum, a timing counter for measuring the
positron time, and a liquid xenon detector for measuring the photon energy,
position and time. The trigger system, the read-out electronics and the data
acquisition system are also presented in detail. The paper is completed with a
description of the equipment and techniques developed for the calibration in
time and energy and the simulation of the whole apparatus.Comment: 59 pages, 90 figure
Measurement of the radiative decay of polarized muons in the MEG experiment
We studied the radiative muon decay by
using for the first time an almost fully polarized muon source. We identified a
large sample (~13000) of these decays in a total sample of 1.8x10^14 positive
muon decays collected in the MEG experiment in the years 2009--2010 and
measured the branching ratio B() =
(6.03+-0.14(stat.)+-0.53(sys.))x10^-8 for E_e > 45 MeV and E_{\gamma} > 40 MeV,
consistent with the Standard Model prediction. The precise measurement of this
decay mode provides a basic tool for the timing calibration, a normalization
channel, and a strong quality check of the complete MEG experiment in the
search for process.Comment: 8 pages, 7 figures. Added an introduction to NLO calculation which
was recently calculated. Published versio
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