86 research outputs found
Endpoint Structure in Decay from Coherent Weak-Interaction of the Neutrino
Recent tritium beta decay experiments yield unphysical negative best-fit values for the square of the neutrino mass. An unidentified bump-like excess of counts few eV below the endpoint in the electron energy spectrum has been tentatively recognized as the source of this anomaly. It is shown that the repulsive potential acting on the emitted antineutrino and originating in its coherent weak-interaction with the daughter atom may effectively account for this excess.Recent tritium beta decay experiments yield unphysical negative best-fit values for the square of the neutrino mass. An unidentified bump-like excess of counts few eV below the endpoint in the electron energy spectrum has been tentatively recognized as the source of this anomaly. It is shown that the repulsive potential acting on the emitted antineutrino and originating in its coherent weak-interaction with the daughter atom may effectively account for this excess
First Characterization of the Ultra-Shielded Chamber in the Low-noise Underground Laboratory (LSBB) of Rustrel Pays d'Apt
In compliance with international agreements on nuclear weapons limitation,
the French ground-based nuclear arsenal has been decommissioned in its
totality. One of its former underground missile control centers, located in
Rustrel, 60 km east of Avignon (Provence) has been converted into the
``Laboratoire Souterrain \`a Bas Bruit de Rustrel-Pays d'Apt'' (LSBB). The
deepest experimental hall (500 m of calcite rock overburden) includes a 100
m area of sturdy flooring suspended by and resting on shock absorbers,
entirely enclosed in a 28 m-long, 8 m-diameter, 1 cm-thick steel Faraday cage.
This results in an unparalleled combination of shielding against cosmic rays,
acoustic, seismic and electromagnetic noise, which can be exploited for rare
event searches using ultra low-temperature and superconducting detectors. The
first characterization measurements in this unique civilian site are reported.
For more info see http://home.cern.ch/collar/RUSTREL/rustrel.htmlComment: Homepage and quoted hyperlinks have been updated: see
http://home.cern.ch/collar/RUSTREL/rustrel.htm
Prospects For Identifying Dark Matter With CoGeNT
It has previously been shown that the excess of events reported by the CoGeNT
collaboration could be generated by elastically scattering dark matter
particles with a mass of approximately 5-15 GeV. This mass range is very
similar to that required to generate the annual modulation observed by
DAMA/LIBRA and the gamma rays from the region surrounding the Galactic Center
identified within the data of the Fermi Gamma Ray Space Telescope. To
confidently conclude that CoGeNT's excess is the result of dark matter,
however, further data will likely be needed. In this paper, we make projections
for the first full year of CoGeNT data, and for its planned upgrade. Not only
will this body of data more accurately constrain the spectrum of nuclear recoil
events, and corresponding dark matter parameter space, but will also make it
possible to identify seasonal variations in the rate. In particular, if the
CoGeNT excess is the product of dark matter, then one year of CoGeNT data will
likely reveal an annual modulation with a significance of 2-3. The
planned CoGeNT upgrade will not only detect such an annual modulation with high
significance, but will be capable of measuring the energy spectrum of the
modulation amplitude. These measurements will be essential to irrefutably
confirming a dark matter origin of these events.Comment: 6 pages, 6 figure
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New experimental constraints in a new landscape for composite dark matter
Certain strongly interacting dark matter candidates could have evaded detection, and much work has been done on constraining their parameter space. Recently, it was shown theoretically that the scattering cross section for pointlike dark matter with a nucleus cannot be significantly larger than the geometric cross section of the nucleus. This realization closes the parameter space for pointlike strongly interacting dark matter. However, strongly interacting dark matter is still theoretically possible for composite particles, with much parameter space open. We set new, wide-ranging limits based on data from a novel detector at the University of Chicago. Backgrounds are greatly suppressed by requiring coincidence detection between two spatially separated liquid-scintillator modules. For dark matter , the time of flight would be , whereas for cosmic rays, it would be . We outline ways to greatly increase sensitivity at modest costs
Design and Characterization of a Neutron Calibration Facility for the Study of sub-keV Nuclear Recoils
As part of an experimental effort to demonstrate sensitivity in a large-mass
detector to the ultra-low energy recoils expected from coherent
neutrino-nucleus elastic scattering, we have designed and built a highly
monochromatic 24 keV neutron beam at the Kansas State University Triga Mark-II
reactor. The beam characteristics were chosen so as to mimic the soft recoil
energies expected from reactor antineutrinos in a variety of targets, allowing
to understand the response of dedicated detector technologies in this yet
unexplored sub-keV recoil range. A full characterization of the beam properties
(intensity, monochromaticity, contaminations, beam profile) is presented,
together with first tests of the calibration setup using proton recoils in
organic scintillator.Comment: submitted to Nucl. Instr. Meth.
The kinetic dark-mixing in the light of CoGENT and XENON100
Several string or GUT constructions motivate the existence of a dark U(1)_D
gauge boson which interacts with the Standard Model only through its kinetic
mixing. We compute the dark matter abundance in such scenario and the
constraints in the light of the recent data from CoGENT, CDMSII and XENON100.
We show in particular that a region with relatively light WIMPS, M_{Z_D}< 40
GeV and a kinetic mixing 10^-4 < delta < 10^-3 is not yet excluded by the last
experimental data and seems to give promising signals in a near future. We also
compute the value of the kinetic mixing needed to explain the
DAMA/CoGENT/CRESST excesses and find that for M_{Z_D}< 30 GeV, delta ~ 10^-3 is
sufficient to fit with the data.Comment: 6 pages, 5figure
Beta Irradiation of a Geometrically Metastable Superconducting Strip Detector with a Magnetic Flux Penetration Read-Out
Geometrical metastability, observed in superconducting type I tin flat
strips, has been previously proposed as a principle for particle detection. The
energy deposition of an incoming beta-particle induces the rupture of the
metastability and consequently the penetration of multiquantum flux tubes into
a superconducting tin strip. We present here the first absorption spectra from
two beta sources, which demonstrate the linearity and energy-resolution of
these detectors (presented at the 6th International Workshop on Low Temperature
Detectors for Dark Matter and Neutrinos (LTD-6), Interlaken, Switzerland, Sept.
1995)Comment: Compressed PostScript (filename.ps.Z), 8 pages, 2 figure
Nuclear Tracks from Cold Dark Matter Interactions in Mineral Crystals: A Computational Study
Recoiling nuclei from Cold Dark Matter (CDM) elastic scattering interactions
with the constituent elements of some minerals may produce etchable damage
tracks in the crystal structure. Present calculations show that in muscovite
mica, CDM tracks from recoiling potassium atoms could be readily distinguished
from others due to alpha-decays in the uranium and thorium chains. Under
favorable conditions, this technique could greatly improve the existing limits
on Weakly Interacting Massive Particles as the constituents of the galactic
halo.Comment: PostScript, 15 pages, 3 figure
Low-background applications of MICROMEGAS detector technology
The MICROMEGAS detector concept, generally optimized for use in accelerator
experiments, displays a peculiar combination of features that can be
advantageous in several astroparticle and neutrino physics applications. Their
sub-keV ionization energy threshold, excellent energy and space resolution, and
a simplicity of design that allows the use of radioclean materials in their
construction are some of these characteristics. We envision tackling
experimental challenges such as the measurement of neutral-current
neutrino-nucleus coherent scattering or Weakly Interacting Massive Particle
(WIMP) detectors with directional sensitivity. The large physics potential of a
compact (total volume O(1)m), multi-purpose array of low-background
MICROMEGAS is made evident.Comment: 5 pg, presented at IMAGING-2000, Stockholm, June 2000. To appear in
Nucl. Instr. & Meth. Final version after referees' inpu
The ZZ' kinetic mixing in the light of the recent direct and indirect dark matter searches
Several constructions, of stringy origins or not, generate abelian gauge
extensions of the Standard Model (SM). Even if the particles of the SM are not
charged under this extra , one cannot avoid the presence of a kinetic
mixing between and the hypercharge . In this work, we
constraint drastically this kinetic mixing, taking into account the recent
experimental data from accelerator physics, direct detection and indirect
detection of dark matter. We show that the region respecting WMAP and
experimental constraints is now very narrowed along the pole line where
, being the gauge boson associated to the extra
.Comment: 9 pages, 3 figures, final version to appear in JCA
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