2,078 research outputs found
Exothermic isospin-violating dark matter after SuperCDMS and CDEX
We show that exothermic isospin-violating dark matter (IVDM) can make the
results of the latest CDMS-Si experiment consistent with recent null
experiments, such as XENON10, XENON100, LUX, CDEX, and SuperCDMS, whereas for
the CoGeNT experiment, a strong tension still persists. For CDMS-Si, separate
exothermic dark matter or isospin-violating dark matter cannot fully ameliorate
the tensions among these experiments; the tension disappears only if exothermic
scattering is combined with an isospin-violating effect of f_n/f_p=-0.7. For
such exothermic IVDM to exist, at least a new vector gauge boson (dark photon
or dark Z') that connects SM quarks to Majorana-type DM particles is required.Comment: 12 pages, 6 figure
Atomic ionization by sterile-to-active neutrino conversion and constraints on dark matter sterile neutrinos with germanium detectors
The transition magnetic moment of a sterile-to-active neutrino conversion
gives rise to not only radiative decay of a sterile neutrino, but also its
non-standard interaction (NSI) with matter. For sterile neutrinos of keV-mass
as dark matter candidates, their decay signals are actively searched for in
cosmic X-ray spectra. In this work, we consider the NSI that leads to atomic
ionization, which can be detected by direct dark matter experiments. It is
found that this inelastic scattering process for a nonrelativistic sterile
neutrino has a pronounced enhancement in the differential cross section at
energy transfer about half of its mass, manifesting experimentally as peaks in
the measurable energy spectra. The enhancement effects gradually smear out as
the sterile neutrino becomes relativistic. Using data taken with germanium
detectors that have fine energy resolution in keV and sub-keV regimes,
constraints on sterile neutrino mass and its transition magnetic moment are
derived and compared with those from astrophysical observations
Derivations of Atomic Ionization Effects Induced by Neutrino Magnetic Moments
A recent paper [M.B. Voloshin, Phys. Rev. Lett. 105, 201801 (2010)] pointed
out that our earlier derivations of atomic ionization cross-section due to
neutrino magnetic moments (arXiv:1001.2074v2) involved unjustified assumptions.
We confirm and elaborate on this comment with these notes. We caution that the
results of the sum-rule approach in this paper contradict the expected
behaviour in atomic transitions.Comment: V3 3 pages ; confirm and elaborate on unjustified assumptions in V1 &
V
Direct measurement of neutrons induced in lead by cosmic muons at a shallow underground site
Neutron production in lead by cosmic muons has been studied with a Gadolinium
doped liquid scintillator detector. The detector was installed next to the
Muon-Induced Neutron Indirect Detection EXperiment (MINIDEX), permanently
located in the T\"ubingen shallow underground laboratory where the mean muon
energy is approximately 7 GeV. The MINIDEX plastic scintillators were used to
tag muons; the neutrons were detected through neutron capture and
neutron-induced nuclear recoil signals in the liquid scintillator detector.
Results on the rates of observed neutron captures and nuclear recoils are
presented and compared to predictions from GEANT4-9.6 and GEANT4-10.3. The
predicted rates are significantly too low for both versions of GEANT4. For
neutron capture events, the observation exceeds the predictions by factors of and for GEANT4-9.6
and GEANT4-10.3, respectively. For neutron nuclear recoil events, which require
neutron energies above approximately 5 MeV, the factors are even larger, and , respectively.
Also presented is the first statistically significant measurement of the
spectrum of neutrons induced by cosmic muons in lead between 5 and 40 MeV. It
was obtained by unfolding the nuclear recoil spectrum. The observed neutron
spectrum is harder than predicted by GEANT4. An investigation of the
distribution of the time difference between muon tags and nuclear recoil
signals confirms the validity of the unfolding procedure and shows that GEANT4
cannot properly describe the time distribution of nuclear recoil events. In
general, the description of the data is worse for GEANT4-10.3 than for
GEANT4-9.6.Comment: 29 pages, 22 figures, 4 table
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