54 research outputs found
Bioconversion of lignocellulosic 'waste' to high-value food proteins: Recombinant production of bovine and human alpha(S1)-casein based on wheat straw lignocellulose
Deep-underground dark matter search with a COSINUS detector prototype
Sodium iodide (NaI) based cryogenic scintillating calorimeters using quantum
sensors for signal read out have shown promising first results towards a
model-independent test of the annually modulating signal detected by the
DAMA/LIBRA dark matter experiment. The COSINUS collaboration has previously
reported on the first above-ground measurements using a dual channel readout of
phonons and light based on transition edge sensors (TESs) that allows for
particle discrimination on an event-by-event basis. In this letter, we outline
the first underground measurement of a NaI cryogenic calorimeter read out via
the novel remoTES scheme. A 3.67 g NaI absorber with an improved silicon light
detector design was operated at the Laboratori Nazionali del Gran Sasso, Italy.
A significant improvement in the discrimination power of /-events
to nuclear recoils was observed with a five-fold improvement in the nuclear
recoil baseline resolution, achieving = 441 eV. Furthermore, we
present a limit on the spin-independent dark-matter nucleon elastic scattering
cross-section achieving a sensitivity of (pb) with an exposure of
only 11.6 g d.Comment: 11 pages, 14 figure
Towards an automated data cleaning with deep learning in CRESST
The CRESST experiment employs cryogenic calorimeters for the sensitive
measurement of nuclear recoils induced by dark matter particles. The recorded
signals need to undergo a careful cleaning process to avoid wrongly
reconstructed recoil energies caused by pile-up and read-out artefacts. We
frame this process as a time series classification task and propose to automate
it with neural networks. With a data set of over one million labeled records
from 68 detectors, recorded between 2013 and 2019 by CRESST, we test the
capability of four commonly used neural network architectures to learn the data
cleaning task. Our best performing model achieves a balanced accuracy of 0.932
on our test set. We show on an exemplary detector that about half of the
wrongly predicted events are in fact wrongly labeled events, and a large share
of the remaining ones have a context-dependent ground truth. We furthermore
evaluate the recall and selectivity of our classifiers with simulated data. The
results confirm that the trained classifiers are well suited for the data
cleaning task.Comment: 12 pages, 8 figures, 6 table
Particle discrimination in a NaI crystal using the COSINUS remote TES design
The COSINUS direct dark matter experiment situated at Laboratori Nazionali
del Gran Sasso in Italy is set to investigate the nature of the annually
modulating signal detected by the DAMA/LIBRA experiment. COSINUS has already
demonstrated that sodium iodide crystals can be operated at mK temperature as
cryogenic scintillating calorimeters using transition edge sensors, despite the
complication of handling a hygroscopic and low melting point material. With
results from a new COSINUS prototype, we show that particle discrimination on
an event-by-event basis in NaI is feasible using the dual-channel readout of
both phonons and scintillation light. The detector was mounted in the novel
remoTES design and operated in an above-ground facility for 9.06 gd of
exposure. With a 3.7 g NaI crystal, e/ events could be clearly
distinguished from nuclear recoils down to the nuclear recoil energy threshold
of 15 keV.Comment: 7 pages, 9 figure
Observation of a low energy nuclear recoil peak in the neutron calibration data of the CRESST-III Experiment
New-generation direct searches for low mass dark matter feature detection
thresholds at energies well below 100 eV, much lower than the energies of
commonly used X-ray calibration sources. This requires new calibration sources
with sub-keV energies. When searching for nuclear recoil signals, the
calibration source should ideally cause mono-energetic nuclear recoils in the
relevant energy range. Recently, a new calibration method based on the
radiative neutron capture on W with subsequent de-excitation via single
-emission leading to a nuclear recoil peak at 112 eV was proposed. The
CRESST-III dark matter search operated several CaWO-based detector
modules with detection thresholds below 100 eV in the past years. We report the
observation of a peak around the expected energy of 112 eV in the data of three
different detector modules recorded while irradiated with neutrons from
different AmBe calibration sources. We compare the properties of the observed
peaks with Geant-4 simulations and assess the prospects of using this for the
energy calibration of CRESST-III detectors.Comment: 8 pages, 4 figures; submitted to Phys. Rev.
Testing spin-dependent dark matter interactions with lithium aluminate targets in CRESST-III
In the past decades, numerous experiments have emerged to unveil the nature
of dark matter, one of the most discussed open questions in modern particle
physics. Among them, the CRESST experiment, located at the Laboratori Nazionali
del Gran Sasso, operates scintillating crystals as cryogenic phonon detectors.
In this work, we present first results from the operation of two detector
modules which both have 10.46 g LiAlO targets in CRESST-III. The lithium
contents in the crystal are Li, with an odd number of protons and neutrons,
and Li, with an odd number of protons. By considering both isotopes of
lithium and Al, we set the currently strongest cross section upper
limits on spin-dependent interaction of dark matter with protons and neutrons
for the mass region between 0.25 and 1.5 GeV/c.Comment: 9 pages, 8 figure
Latest observations on the low energy excess in CRESST-III
The CRESST experiment observes an unexplained excess of events at low
energies. In the current CRESST-III data-taking campaign we are operating
detector modules with different designs to narrow down the possible
explanations. In this work, we show first observations of the ongoing
measurement, focusing on the comparison of time, energy and temperature
dependence of the excess in several detectors. These exclude dark matter,
radioactive backgrounds and intrinsic sources related to the crystal bulk as a
major contribution.Comment: 10 pages, 5 figures; to be published in IDM2022 proceeding
High-Dimensional Bayesian Likelihood Normalisation for CRESST's Background Model
Using CaWO crystals as cryogenic calorimeters, the CRESST experiment
searches for nuclear recoils caused by the scattering of potential Dark Matter
particles. A reliable identification of a potential signal crucially depends on
an accurate background model. In this work we introduce an improved
normalisation method for CRESST's model of the electromagnetic backgrounds.
Spectral templates, based on Geant4 simulations, are normalised via a Bayesian
likelihood fit to experimental background data. Contrary to our previous work,
no assumption of partial secular equilibrium is required, which results in a
more robust and versatile applicability. Furthermore, considering the
correlation between all background components allows us to explain 82.7% of the
experimental background within [1 keV, 40 keV], an improvement of 18.6%
compared to our previous method.Comment: 24 pages, 14 figures, submitted to EPJ
Results on sub-GeV Dark Matter from a 10 eV Threshold CRESST-III Silicon Detector
We present limits on the spin-independent interaction cross section of dark
matter particles with silicon nuclei, derived from data taken with a cryogenic
calorimeter with 0.35 g target mass operated in the CRESST-III experiment. A
baseline nuclear recoil energy resolution of eV,
currently the lowest reported for macroscopic particle detectors, and a
corresponding energy threshold of eV have been
achieved, improving the sensitivity to light dark matter particles with masses
below 160 MeV/c by a factor of up to 20 compared to previous results. We
characterize the observed low energy excess, and we exclude noise triggers and
radioactive contaminations on the crystal surfaces as dominant contributions.Comment: 8 pages, 5 figures; precised the position of the calibration source
in Fig. 1; extended the discussion about the observed energy spectrum; added
the DM limit curve to ancillary files. Published in Phys. Rev.
Detector development for the CRESST experiment
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.Comment: 8 pages, 4 figure
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