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.
Diamond operated as a cryogenic calorimeter is an excellent target for direct
detection of low-mass dark matter candidates. Following the realization of the
first low-threshold cryogenic detector ...that uses diamond as absorber for
astroparticle physics applications, we now present the resulting exclusion
limits on the elastic spin-independent interaction cross-section of dark matter
with diamond. We measured two 0.175 g CVD (Chemical Vapor Deposition) diamond
samples, each instrumented with a W-TES. Thanks to the energy threshold of just
16.8 eV of one of the two detectors, we set exclusion limits on the elastic
spin-independent interaction of dark matter particles with carbon nuclei down
to dark matter masses as low as 0.122 GeV/c2. This work shows the scientific
potential of cryogenic detectors made from diamond and lays the foundation for
the use of this material as target for direct detection dark matter
experiments.
The response to angiotensin-converting enzyme inhibitors (ACEIs) can be of considerable help in the diagnosis of human renovascular hypertension (RVH) in three settings. First, a particularly ...dramatic antihypertensive response or a decline in glomerular filtration rate (GFR), as indexed by a rise in serum creatinine or blood urea nitrogen concentrations, are useful clues to the presence of renovascular hypertension. Second, an exaggerated rise in plasma renin activity (PRA) after short-term captopril administration is a very promising screening test for this condition. Third, ACEI-induced changes in single-kidney hemodynamics (assessed by renography) may be helpful in confirming the diagnosis and offers the prospect of localizing the ischemic kidney.
209Bi alpha decay to the ground and to the first excited state have been recently observed for the first time with a large BGO scintillating bolometer. The half-life of 209Bi is determined to be ...τ(1/2)=(2.01±0.08)×10(19) yr while the branching ratio for the ground-state to ground-state transition is (98.8±0.3)%.
After an introduction on the various experimental techniques to be adopted in searches for double beta decay, the new approach based on the use of cryogenic low temperature detectors is described. ...The present results are reported on the limit for neutrinoless double beta decay of
130Te obtained with the large bolometric detector CUORICINO. This setup consists of 44 cubic crystals of natural TeO
2 with 5 cm sides and 18 crystals of 3×3×6 cm
3. Four of these latter crystals are made with isotopically enriched materials: two in
128Te and two others in
130Te. With a sensitive mass of 40.7 kg, this array is by far the most massive running cryogenic detector. The array is operated at a temperature of ∼10 mK in a dilution refrigerator under a heavy shield in the Gran Sasso Underground Laboratory at a depth of about 3500 m.w.e. The counting rate in the region of neutrinoless double beta decay is 0.18±0.02 counts keV
−1 kg
−1 y
−1, among the lowest in this type of experiment. No evidence for neutrinoless double beta decay is found. The corresponding lower limit for the lifetime of this process is 2×10
24 years at 90% C.L. The resultant upper limit on the effective neutrino mass ranges between 0.2 and 1.0 eV, depending on the theoretically calculated nuclear matrix elements. This constraint is the most restrictive one, except for those obtained with Ge diodes, and is comparable to them. The second part of this report is devoted to the present status of the construction of the larger experiment CUORE (Cryogenic Underground Observatory for Rare Events) formed from 988 bolometers with a cubic TeO
2 absorber of size 5×5×5 cm
3, with a total mass of ∼750 kg. We present technical details of the CUORE setup as well as of its location and our efforts to reduce radioactive backgrounds.
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 \(^{182}\)W with subsequent de-excitation via single \(\gamma\)-emission leading to a nuclear recoil peak at 112 eV was proposed. The CRESST-III dark matter search operated several CaWO\(_{4}\)-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.
Using CaWO\(_4\) 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.
Rab proteins are small molecular mass GTP-ases involved in the regulation of vescicular transport. The ability of rab proteins to carry out their role in intracellular membrane traffic requires the ...post-translational attachment to their C-terminus of a geranylgeranyl group, an isoprenoid lipid moiety derived from mevalonate. Here we report that depletion of intracellular mevalonate by lovastatin in FRTL-5 thyroid cells specifically resulted in a four-fold increase of Rab5 and Rab7 protein levels. This increase was reversed within 4 h upon addition of mevalonate. Similarly lovastatin also induced, at same extent, mRNA levels. Lovastatin effect was not common to other prenylated proteins. Moreover incubation with cycloheximide abolished the observed increase in lovastatin treated cells, suggesting that the effect is mediated by newly synthesized protein. These findings demonstrate that Rab5 and Rab7 expression are regulated by the isoprenoid pathway.
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 \((1.36\pm 0.05)\) eV\(_{\text{nr}}\), currently the lowest reported for macroscopic particle detectors, and a corresponding energy threshold of \((10.0\pm 0.2)\) eV\(_{\text{nr}}\) have been achieved, improving the sensitivity to light dark matter particles with masses below 160 MeV/c\(^2\) 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.
PDF
