216 research outputs found
Cryogenic light detectors with enhanced performance for rare events physics
We have developed and tested a new way of coupling bolometric light detectors
to scintillating crystal bolometers based upon simply resting the light
detector on the crystal surface, held in position only by gravity. This
straightforward mounting results in three important improvements: (1) it
decreases the amount of non-active materials needed to assemble the detector,
(2) it substantially increases the light collection efficiency by minimizing
the light losses induced by the mounting structure, and (3) it enhances the
thermal signal induced in the light detector thanks to the extremely weak
thermal link to the thermal bath. We tested this new technique with a 16 cm
Ge light detector with thermistor readout sitting on the surface of a large
TeO bolometer. The light collection efficiency was increased by greater
than 50\% compared to previously tested alternative mountings. We obtained a
baseline energy resolution on the light detector of 20~eV RMS that, together
with increased light collection, enabled us to obtain the best vs
discrimination ever obtained with massive TeO crystals. At
the same time we achieved rise and decay times of 0.8 and 1.6 ms, respectively.
This superb performance meets all of the requirements for the CUPID (CUORE
Upgrade with Particle IDentification) experiment, which is a 1-ton
scintillating bolometer follow up to CUORE.Comment: 6 pages, 4 figure
TeO bolometers with Cherenkov signal tagging: towards next-generation neutrinoless double beta decay experiments
CUORE, an array of 988 TeO bolometers, is about to be one of the most
sensitive experiments searching for neutrinoless double-beta decay. Its
sensitivity could be further improved by removing the background from
radioactivity. A few years ago it has been pointed out that the signal from
s can be tagged by detecting the emitted Cherenkov light, which is not
produced by s. In this paper we confirm this possibility. For the first
time we measured the Cherenkov light emitted by a CUORE crystal, and found it
to be 100 eV at the -value of the decay. To completely reject the
background, we compute that one needs light detectors with baseline noise below
20 eV RMS, a value which is 3-4 times smaller than the average noise of the
bolometric light detectors we are using. We point out that an improved light
detector technology must be developed to obtain TeO bolometric experiments
able to probe the inverted hierarchy of neutrino masses.Comment: 5 pages, 4 figures. Added referee correction
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
The CRESST II Dark Matter Search
Direct Dark Matter detection with cryodetectors is briefly discussed, with
particular mention of the possibility of the identification of the recoil
nucleus. Preliminary results from the CREEST II Dark Matter search, with 730
kg-days of data, are presented. Major backgrounds and methods of identifying
and dealing with them are indicated.Comment: Talk at DSU workshop, ITP Beijing, Oct. 2011. 9 figures, 2 table
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