1,579 research outputs found
Gamma Ray Spectroscopy with Scintillation Light in Liquid Xenon
Scintillation light from gamma ray irradiation in liquid xenon is detected by
two Hamamatsu R9288 photomultiplier tubes (PMTs) immersed in the liquid. UV
light reflector material, PTFE, is used to optimize the light collection
efficiency. The detector gives a high light yield of 6 photoelectron per keV
(pe/keV), which allows efficient detection of the 122 keV gamma-ray line from
Co-57, with a measured energy resolution of (8.8+/-0.6)% (sigma). The best
achievable energy resolution, by removing the instrumental fluctuations, from
liquid xenon scintillation light is estimated to be around 6-8% (sigma) for
gamma-ray with energy between 662 keV and 122 keV
Design and Performance of the XENON10 Dark Matter Experiment
XENON10 is the first two-phase xenon time projection chamber (TPC) developed
within the XENON dark matter search program. The TPC, with an active liquid
xenon (LXe) mass of about 14 kg, was installed at the Gran Sasso underground
laboratory (LNGS) in Italy, and operated for more than one year, with excellent
stability and performance. Results from a dark matter search with XENON10 have
been published elsewhere. In this paper, we summarize the design and
performance of the detector and its subsystems, based on calibration data using
sources of gamma-rays and neutrons as well as background and Monte Carlo
simulations data. The results on the detector's energy threshold, energy and
position resolution, and overall efficiency show a performance that exceeds
design specifications, in view of the very low energy threshold achieved (<10
keVr) and the excellent energy resolution achieved by combining the ionization
and scintillation signals, detected simultaneously
Compton scattering sequence reconstruction algorithm for the liquid xenon gamma-ray imaging telescope (LXeGRIT)
The Liquid Xenon Gamma-Ray Imaging Telescope (LXeGRIT) is a balloon born
experiment sensitive to \g -rays in the energy band of 0.2-20 MeV. The main
detector is a time projection chamber filled with high purity liquid xenon
(LXeTPC), in which the three-dimensional location and energy deposit of
individual \g -ray interactions are accurately measured in one homogeneous
volume. To determine the \g -ray initial direction (Compton imaging), as well
as to reject background, the correct sequence of interactions has to be
determined. Here we report the development and optimization of an algorithm to
reconstruct the Compton scattering sequence and show its performance on Monte
Carlo events and LXeGRIT data.Comment: To appear in: Hard X-Ray, Gamma-Ray, and Neutron Detector Physics II,
2000; Proc. SPIE, vol. 4141; R.B. James & R.C. Schirato, ed
Can WIMP Dark Matter overcome the Nightmare Scenario?
Even if new physics beyond the Standard Model (SM) indeed exists, the energy
scale of new physics might be beyond the reach at the Large Hadron Collider
(LHC) and the LHC could find only the Higgs boson but nothing else. This is the
so-called "nightmare scenario". On the other hand, the existence of the dark
matter has been established from various observations. One of the promising
candidates for thermal relic dark matter is a stable and electric
charge-neutral Weakly Interacting Massive Particle (WIMP) with the mass below
the TeV scale. In the nightmare scenario, we introduce a WIMP dark matter
singlet under the SM gauge group, which only couples to the Higgs doublet at
the lowest order, and investigate a possibility that such WIMP dark matter can
be a clue to overcome the nightmare scenario via various phenomenological tests
such as the dark matter relic abundance, the direct detection experiments for
the dark matter particle, and the production of the dark matter particle at the
LHC.Comment: 14 pages, 10 figure
Constraints on Scalar Phantoms
We update the constraints on the minimal model of dark matter, where a stable
real scalar field is added to the standard model Lagrangian with a
renormalizable coupling to the Higgs field. Once we fix the dark matter
abundance, there are only two relevant model parameters, the mass of the scalar
field and that of the Higgs boson. The recent data from the CDMS II experiment
have excluded a parameter region where the scalar field is light such as less
than about 50 GeV. In a large parameter region, the consistency of the model
can be tested by the combination of future direct detection experiments and the
LHC experiments.Comment: 7 pages, 1 figur
Exotic fermion multiplets as a solution to baryon asymmetry, dark matter and neutrino masses
We propose an extension to the standard model where three exotic fermion
5-plets and one scalar 6-plet are added to the particle content. By demanding
that all interactions are renormalizable and standard model gauge invariant, we
show that the lightest exotic particle in this model can be a dark matter
candidate as long as the new 6-plet scalar does not develop a nonzero vacuum
expectation value. Furthermore, light neutrino masses are generated radiatively
at one-loop while the baryon asymmetry is produced by the CP-violating decays
of the second lightest exotic particle. We have demonstrated using concrete
examples that there is a parameter space where a consistent solution to the
problems of baryon asymmetry, dark matter and neutrino masses can be obtained.Comment: 17 pages, 2 figures (REVTeX4.1), v2: some refs added, v3: typos
corrected, Sec.VI.B, C modified, this version to appear in PR
Gator: a low-background counting facility at the Gran Sasso Underground Laboratory
A low-background germanium spectrometer has been installed and is being
operated in an ultra-low background shield (the Gator facility) at the Gran
Sasso underground laboratory in Italy (LNGS). With an integrated rate of ~0.16
events/min in the energy range between 100-2700 keV, the background is
comparable to those of the world's most sensitive germanium detectors. After a
detailed description of the facility, its background sources as well as the
calibration and efficiency measurements are introduced. Two independent
analysis methods are described and compared using examples from selected sample
measurements. The Gator facility is used to screen materials for XENON, GERDA,
and in the context of next-generation astroparticle physics facilities such as
DARWIN.Comment: 14 pages, 6 figures, published versio
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