The CRESST experiment is a direct dark matter search which aims to measure interactions of potential dark matter particles in an Earth-bound detector. With the current stage, CRESST-III, we focus on ...a low energy threshold for increased sensitivity towards light dark matter particles. In this paper we describe the analysis of one detector operated in the first run of CRESST-III (05/2016–02/2018) achieving a nuclear recoil threshold of 30.1 eV. This result was obtained with a 23.6 g CaWO4 crystal operated as a cryogenic scintillating calorimeter in the CRESST setup at the Laboratori Nazionali del Gran Sasso (LNGS). Both the primary phonon (heat) signal and the simultaneously emitted scintillation light, which is absorbed in a separate silicon-on-sapphire light absorber, are measured with highly sensitive transition edge sensors operated at ∼15 mK. The unique combination of these sensors with the light element oxygen present in our target yields sensitivity to dark matter particle masses as low as 160 MeV/c2.
The CRESST experiment (Cryogenic Rare Even Search with Superconducting Thermometers), located at Laboratori Nazionali del Gran Sasso in Italy, searches for dark matter particles via their elastic ...scattering off nuclei in a target material. The CRESST target consists of scintillating CaWO4 crystals, which are operated as cryogenic calorimeters at millikelvin temperatures. Each interaction in the CaWO4 target crystal produces a phonon signal and a light signal that is measured by a second cryogenic calorimeter. Since the CRESST-II result in 2015, the experiment is leading the field of direct dark matter search for dark matter masses below 1.7 GeV/c2, extending the reach of direct searches to the sub-GeV/c2 mass region. For CRESST-III, whose Phase 1 started in July 2016, detectors have been optimized to reach the performance required to further probe the low-mass region with unprecedented sensitivity. In this contribution the achievements of the CRESST-III detectors will be discussed together with preliminary results and perspectives of Phase 1.
Models for light dark matter particles with masses below 1 GeV/c Formula omitted 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 Formula omitted-cleus experiment has achieved an energy threshold of Formula omitted eV. This is one order of magnitude lower than for previous devices 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 and 500 MeV/c Formula omitted.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In this work, we want to highlight the potential of lithium as a target for spin-dependent dark matter search in cryogenic experiments, with a special focus on the low-mass region of the parameter ...space. We operated a prototype detector module based on a Formula omitted target crystal in an above-ground laboratory. Despite the high background environment, the detector sets a competitive limit on spin-dependent interactions of dark matter particles with protons and neutrons for masses between Formula omitted and Formula omitted.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Abstract
The development of low-threshold detectors for the study of
coherent elastic neutrino-nucleus scattering and for the search for
light dark matter necessitates methods of low-energy ...calibration. We
suggest this can be provided by the nuclear recoils resulting from
the γ emission following thermal neutron capture. In
particular, several MeV-scale single-γ transitions induce
well-defined nuclear recoil peaks in the 100 eV range. Using the
FIFRELIN code, complete schemes of γ-cascades for various
isotopes can be predicted with high accuracy to determine the
continuous background of nuclear recoils below the calibration
peaks. We present a comprehensive experimental concept for the
calibration of CaWO
4
and Ge cryogenic detectors at a research
reactor. For CaWO
4
the simulations show that two nuclear recoil
peaks at 112.5 eV and 160.3 eV should be visible above background
simply in the spectrum of the cryogenic detector. Then we discuss
how the additional tagging for the associated γ increases the
sensitivity of the method and extends its application to a wider
energy range and to Ge cryogenic detectors.
Recently low-mass dark matter direct searches have been hindered by a low-energy background, drastically reducing the physics reach of the experiments. In the CRESST-III experiment, this signal is ...characterised by a significant increase of events below 200 eV. As the origin of this background is still unknown, it became necessary to develop new detector designs to reach a better understanding of the observations. Within the CRESST collaboration, three new different detector layouts have been developed, and they are presented in this contribution.
CRESST is a leading direct detection sub-GeVc−2 dark matter experiment. During its second phase, cryogenic bolometers were used to detect nuclear recoils off the CaWO4 target crystal nuclei. The ...previously established electromagnetic background model relies on Secular Equilibrium (SE) assumptions. In this work, a validation of SE is attempted by comparing two likelihood-based normalisation results using a recently developed spectral template normalisation method based on Bayesian likelihood. Albeit we find deviations from SE in some cases we conclude that these deviations are artefacts of the fit and that the assumptions of SE is physically meaningful.
•Novel assessment of secular equilibrium assumptions in a CaWO4 cryogenic crystal.•Bayesian likelihood normalisation method of spectral templates.•Comparison between fits with and without secular equilibrium assumptions.•Deviations found -> effects of the fit; SE assumptions validated.
Cryogenic Rare Event Search with Superconducting Thermometers (CRESST) is a long-standing direct dark matter detection experiment with cryogenic detectors located at the underground facility ...Laboratori Nazionali del Gran Sasso in Italy. CRESST-III, the third generation of CRESST, was specifically designed to have a world-leading sensitivity for low-mass dark matter (DM) (less than 2 GeV/
c
2
) to probe the spin-independent DM-nucleus cross section. At present, a large part of the parameter space for spin-independent scattering off nuclei remains untested for dark matter particles with masses below few GeV/
c
2
although many motivated theoretical models having been proposed. The CRESST-III experiment employs scintillating
CaWO
4
crystals of
∼
25 g as target material for dark matter interactions operated as cryogenic scintillating calorimeters at
∼
10 mK. CRESST-III first data taking was successfully completed in 2018, achieving an unprecedented energy threshold for nuclear recoils. This result extended the present sensitivity to DM particles as light as
∼
160 MeV/
c
2
. In this paper, an overview of the CRESST-III detectors and results will be presented.
The Cryogenic Rare Event Search with Superconducting Thermometers (CRESST) experiment aims at the direct detection of dark matter particles via their elastic scattering off nuclei in a scintillating ...CaWO
4
target crystal. The CaWO
4
crystal is operated together with a light detector at mK temperature and read out by a Transition Edge Sensor. For many years, CaWO
4
crystals have successfully been produced in-house at Technical University of Munich (TUM) with a focus on high radiopurity which is crucial to reduce background originating from radioactive contamination. In order to further improve the CaWO
4
crystals, an extensive chemical purification of the raw materials and the synthesised CaWO
4
powder has been performed. In addition, a temperature gradient simulation of the growth process and subsequently an optimisation of the growth furnace with the goal to reduce the intrinsic stress was carried out. We present results on the intrinsic stress in the CaWO
4
crystals and on the CaWO
4
powder radiopurity. A crystal grown from the purified material was installed in the current CRESST set-up. The detector is equipped with an instrumented holder which is used to measure the alpha decay rate of the crystal. We present a preliminary analysis showing a significantly reduced intrinsic background from natural decay chains.
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