arXiv subjects

A. Münster

Publications and source records attributed to A. Münster.

25 records · Page 2Linked to original sources

arXiv2015

Low-Temperature Scintillation Properties of CaWO4 Crystals for Rare-Event Searches

In prospect of its application in cryogenic rare-event searches, we have investigated the low-temperature scintillation properties of CaWO4 crystals down to 3.4 K under α and γ excitation. Concerning the scintillation decay times, we observe a long component in the ms range which significantly contributes to the light yield below 40K. For the first time we have measured the temperature dependence of the α/γ- ratio of the light yield. This parameter which can be used to discriminate α and γ events in scintillating bolometers is found to be about 8-15% smaller at low temperatures compared to room temperature.

physics.ins-det↗

arXiv2015

The CRESST Dark Matter Search - Status and Perspectives

In the past years the spotlight of the search for dark matter particles widened to the low mass region, both from theoretical and experimental side. We discuss results from data obtained in 2013 with a single detector TUM40. This detector is equipped with a new upgraded holding scheme to efficiently veto backgrounds induced by surface alpha decays. This veto, the low threshold of 0.6keV and an unprecedented background level for CaWO$_4$ target crystals render TUM40 the detector with the best overall performance of CRESST-II phase 2 (July 2013 - August 2015). A low-threshold analysis allowed to investigate light dark matter particles (<3GeV/c$^2$), previously not accessible for other direct detection experiments.

physics.ins-det↗

arXiv2015

Probing low WIMP masses with the next generation of CRESST detector

The purpose of this document is to describe the upgrade of the CRESST dark matter search at LNGS. The proposed strategy will allow to explore a region of the parameter space for spin-independent WIMP-nucleon elastic scattering corresponding to WIMP masses below 10GeV/c$^\text{2}$, that has not been covered by other experiments. These results can be achieved only with outstanding detector performances in terms of threshold and background. This proposal shows how CRESST can match these performance requirements, adding a unique piece of information to the dark matter puzzle. The results of this program will fix a new state-of-the-art in the low mass WIMP exploration, opening new perspectives of understanding the dark matter scenario.

astro-ph.IM↗

arXiv2015

Impact of Coherent Neutrino Nucleus Scattering on Direct Dark Matter Searches based on CaWO$_4$ Crystals

Atmospheric and solar neutrinos scattering coherently off target nuclei will be an important background source for the next generation of direct dark matter searches. In this work we focus on calcium tungstate as target material. For comparison with existing works we calculate the neutrino floor indicating which sensitivities can be reached before the neutrino background appears. In addition, we investigate the sensitivities of future direct dark matter searches using CRESST-II like detectors. Extending previous works we take into account achievable energy resolutions and thresholds as well as beta and gamma backgrounds for this investigation. We show that an exploration of WIMP-nucleon cross sections below the neutrino floor is possible for exposures of $\gtrsim10$ kg-years or higher. In the third part we show that a first detection of coherent neutrino nucleus scattering of atmospheric and solar neutrinos using the same detectors and the backgrounds is feasible for exposures of $\gtrsim50$ kg-years.

hep-ph↗

arXiv2015

Results on low mass WIMPs using an upgraded CRESST-II detector

The CRESST-II cryogenic dark matter search aims for the detection of WIMPs via elastic scattering off nuclei in CaWO$_4$ crystals. We present results from a low-threshold analysis of a single upgraded detector module. This module efficiently vetoes low energy backgrounds induced by $α$-decays on inner surfaces of the detector. With an exposure of \unit[29.35]{kg live days} collected in 2013 we set a limit on spin-independent WIMP-nucleon scattering which probes a new region of parameter space for WIMP masses below \unit[3]{GeV/c$^2$}, previously not covered in direct detection searches. A possible excess over background discussed for the previous CRESST-II phase 1 (from 2009 to 2011) is not confirmed.

astro-ph.CO↗

arXiv2014

Neganov-Luke amplified cryogenic light detectors for the background discrimination in neutrinoless double beta decay search with TeO$_{2}$ bolometers

We demonstrate that Neganov-Luke amplified cryogenic light detectors with Transition Edge Sensor read-out can be applied for the background suppression in cryogenic experiments searching for the neutrinoless double beta decay of $^{130}\text{Te}$ with TeO$_{2}$ based bolometers. Electron and gamma induced events can be discriminated from $α$ events by detecting the Cherenkov light produced by the $β$ particles emitted in the decay. We use the Cherenkov light produced by events in the full energy peak of $^{208}\text{Tl}$ and by events from a $^{147}\text{Sm}$ source to show that at the Q-value of the neutrinoless double beta decay of $^{130}\text{Te}$ ($Q_{ββ} = 2.53 \,\text{MeV}$), a separation of $e^{-}/γ$ events from $α$ events can be achieved on an event-by-event basis with practically no reduction in signal acceptance.

physics.ins-det↗

arXiv2014

Radiopurity of CaWO$_4$ Crystals for Direct Dark Matter Search with CRESST and EURECA

The direct dark matter search experiment CRESST uses scintillating CaWO$_4$ single crystals as targets for possible WIMP scatterings. An intrinsic radioactive contamination of the crystals as low as possible is crucial for the sensitivity of the detectors. In the past CaWO$_4$ crystals operated in CRESST were produced by institutes in Russia and the Ukraine. Since 2011 CaWO$_4$ crystals have also been grown at the crystal laboratory of the Technische Universität München (TUM) to better meet the requirements of CRESST and of the future tonne-scale multi-material experiment EURECA. The radiopurity of the raw materials and of first TUM-grown crystals was measured by ultra-low background $γ$-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 $α$-activities which were compared to those of crystals produced at other institutes. The total $α$-activities of TUM-grown crystals as low as 1.23 $\pm$ 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.

astro-ph.IM↗