44 research outputs found
Dark-Photon Search using Data from CRESST-II Phase 2
Identifying the nature and origin of dark matter is one of the major
challenges for modern astro and particle physics. Direct dark-matter searches
aim at an observation of dark-matter particles interacting within detectors.
The focus of several such searches is on interactions with nuclei as provided
e.g. by Weakly Interacting Massive Particles. However, there is a variety of
dark-matter candidates favoring interactions with electrons rather than with
nuclei. One example are dark photons, i.e., long-lived vector particles with a
kinetic mixing to standard-model photons. In this work we present constraints
on this kinetic mixing based on data from CRESST-II Phase 2 corresponding to an
exposure before cuts of 52\,kg-days. These constraints improve the existing
ones for dark-photon masses between 0.3 and 0.7\,keV/c.Comment: submitted EPJ
Results on MeV-scale dark matter from a gram-scale cryogenic calorimeter operated above ground
Models for light dark matter particles with masses below 1 GeV/c are a
natural and well-motivated alternative to so-far unobserved weakly interacting
massive particles. Gram-scale cryogenic calorimeters provide the required
detector performance to detect these particles and extend the direct dark
matter search program of CRESST. A prototype 0.5 g sapphire detector developed
for the -cleus experiment has achieved an energy threshold of
eV, which is one order of magnitude lower than previous
results and independent of the type of particle interaction. The result
presented here is obtained in a setup above ground without significant
shielding against ambient and cosmogenic radiation. Although operated in a
high-background environment, the detector probes a new range of light-mass dark
matter particles previously not accessible by direct searches. We report the
first limit on the spin-independent dark matter particle-nucleon cross section
for masses between 140 MeV/c and 500 MeV/c.Comment: 6 pages, 6 figures, v3: ancillary files added, v4: high energy
spectrum (0.6-12keV) added to ancillary file
Results on light dark matter particles with a low-threshold CRESST-II detector
The CRESST-II experiment uses cryogenic detectors to search for nuclear
recoil events induced by the elastic scattering of dark matter particles in
CaWO crystals. Given the low energy threshold of our detectors in
combination with light target nuclei, low mass dark matter particles can be
probed with high sensitivity. In this letter we present the results from data
of a single detector module corresponding to 52 kg live days. A blind analysis
is carried out. With an energy threshold for nuclear recoils of 307 eV we
substantially enhance the sensitivity for light dark matter. Thereby, we extend
the reach of direct dark matter experiments to the sub-region and demonstrate
that the energy threshold is the key parameter in the search for low mass dark
matter particles.Comment: 8 pages, 8 figure
Results from 730 kg days of the CRESST-II Dark Matter Search
The CRESST-II cryogenic Dark Matter search, aiming at detection of WIMPs via
elastic scattering off nuclei in CaWO crystals, completed 730 kg days of
data taking in 2011. We present the data collected with eight detector modules,
each with a two-channel readout; one for a phonon signal and the other for
coincidently produced scintillation light. The former provides a precise
measure of the energy deposited by an interaction, and the ratio of
scintillation light to deposited energy can be used to discriminate different
types of interacting particles and thus to distinguish possible signal events
from the dominant backgrounds. Sixty-seven events are found in the acceptance
region where a WIMP signal in the form of low energy nuclear recoils would be
expected. We estimate background contributions to this observation from four
sources: 1) "leakage" from the e/\gamma-band 2) "leakage" from the
\alpha-particle band 3) neutrons and 4) Pb-206 recoils from Po-210 decay. Using
a maximum likelihood analysis, we find, at a high statistical significance,
that these sources alone are not sufficient to explain the data. The addition
of a signal due to scattering of relatively light WIMPs could account for this
discrepancy, and we determine the associated WIMP parameters.Comment: 17 pages, 13 figure
Radiopurity of CaWO4 crystals for direct dark matter search with CRESST and EURECA
The direct dark matter search experiment CRESST uses scintillating CaWO4 single crystals as targets for possible WIMP scatterings. An intrinsic radioactive contami- nation of the crystals as low as possible is crucial for the sensitivity of the detectors. In the past CaWO4 crystals operated in CRESST were produced by institutes in Russia and the Ukraine. Since 2011 CaWO4 crystals have also been grown at the crystal laboratory of the Technische Universit ¨at Mu ¨nchen (TUM) to better meet the requirements of CRESST and of the future tonne-scale multi-material experiment EURECA. The radiopurity of the raw mate- rials and of first TUM-grown crystals was measured by ultra-low background ¿-spectrometry. Two TUM-grown crystals were also operated as low-temperature detectors at a test setup in the Gran Sasso underground laboratory. These measurements were used to determine the crystals’ intrinsic a-activities which were compared to those of crystals produced at other institutes. The total a-activities of TUM-grown crystals as low as 1.23 ± 0.06 mBq/kg were found to be significantly smaller than the activities of crystals grown at other institutes typically ranging between ~ 15 mBq/kg and ~ 35 mBq/kg