arXiv subjects

S. Rozov

Publications and source records attributed to S. Rozov.

At least 19 recordsLinked to original sources

arXiv2026

First observation of single beta decay of $^{96}$Zr

The single beta decay of $^{96}$Zr has been detected for the first time using a 211 cm$^3$ low-background HPGe detector and an external source consisting of two samples of enriched zirconium (atomic fraction of $^{96}$Zr is 88.28%, total mass is 140.65 g). During the search for the $\beta$ decay of $^{96}$Zr, the $\beta$ decay of the daughter nucleus $^{96}$Nb to the excited states of $^{96}$Mo has been observed. The $\gamma$-ray cascade produced by the $^{96}$Mo nucleus while de-exciting to the ground state has been detected with the HPGe detector. The experiment has been carried out at the Baksan Neutrino Observatory. It has produced 12625.34 h of data. The half-life of the single beta decay of $^{96}$Zr is measured to be $T_{1/2} = [2.27^{+0.53}_{-0.36}(stat) \pm 0.27(syst)]\times10^{20}$ yr.

nucl-ex↗

arXiv2026

First investigation of $^{96}$Zr samples enriched by the gas-centrifuge method for the use in rare-decay studies

For the first time, the isotope $^{96}$Zr has been produced by the gas-centrifuge method (enrichment is 88.28% and full mass of $^{96}$Zr is 179.816 g). The level of radionuclide impurities of the samples and thus their suitability for rare-event search have been investigated using three low-background HPGe detectors. The most stringent limit, obtained at sea level, on the half-life of the double beta decay of $^{96}$Zr to the $0^+_1$ excited state (1148 keV) of $^{96}$Mo has been set $T_{1/2}(0\nu+2\nu)>3.9 \times 10^{19}$ yr (90% C.L.).

nucl-ex↗

arXiv2026

Application of a high-precision distributed uranium source for determining the effective mass and volume of a HPGe detector

A distributed uranium source with the accurately certified activity of 238U has been used to verify the effective mass of the HPGe detector intended for the {\nu}GeN neutrino experiment. The source, dissolved in nitric acid, provides homogeneous irradiation of the detector crystal allowing the study of its mass and volume. The experimental spectra obtained with the distributed source have been compared to the detailed Geant4 Monte Carlo simulations. The measured counting rates of several gamma-lines agree with the simulated efficiencies, confirming that the detector mass and volume coincide with the manufacturer specifications. The results demonstrate the applicability of such sources for mass calibration of HPGe detectors.

physics.ins-det↗

arXiv2025

New constraints on coherent elastic neutrino-nucleus scattering by the nuGeN experiment

The nuGeN experiment searches for coherent elastic neutrino-nucleus scattering (CEvNS) at the Kalinin Nuclear Power Plant. A 1.41-kg high-purity low-threshold germanium detector surrounded by active and passive shielding is deployed at the minimal distance of 11.1 m allowed by the lifting mechanism from the center of reactor core, utilizing one of the highest antineutrino fluxes among the competing experiments. The direct comparison of the count rates obtained during reactor-ON and reactor-OFF periods with the energy threshold of 0.29~keV$_{ee}$ shows no statistically significant difference. New upper limits on the number of CEvNS events are evaluated on the basis of the residual ON$-$OFF count rate spectrum.

hep-ex↗

arXiv2024

Searching for Beyond the Standard Model physics using the improved description of $^{100}$Mo $2\nu\beta\beta$ decay spectral shape with CUPID-Mo

The current experiments searching for neutrinoless double-$\beta$ ($0\nu\beta\beta$) decay also collect large statistics of Standard Model allowed two-neutrino double-$\beta$ ($2\nu\beta\beta$) decay events. These can be used to search for Beyond Standard Model (BSM) physics via $2\nu\beta\beta$ decay spectral distortions. $^{100}$Mo has a natural advantage due to its relatively short half-life, allowing higher $2\nu\beta\beta$ decay statistics at equal exposures compared to the other isotopes. We demonstrate the potential of the dual read-out bolometric technique exploiting a $^{100}$Mo exposure of 1.47 kg $\times$ y, acquired in the CUPID-Mo experiment at the Modane underground laboratory (France). We set limits on $0\nu\beta\beta$ decays with the emission of one or more Majorons, on $2\nu\beta\beta$ decay with Lorentz violation, and $2\nu\beta\beta$ decay with a sterile neutrino emission. In this analysis, we investigate the systematic uncertainty induced by modeling the $2\nu\beta\beta$ decay spectral shape parameterized through an improved model, an effect never considered before. This work motivates searches for BSM processes in the upcoming CUPID experiment, which will collect the largest amount of $2\nu\beta\beta$ decay events among the next-generation experiments.

nucl-ex↗

arXiv2024

Results from a Prototype TES Detector for the Ricochet Experiment

Coherent elastic neutrino-nucleus scattering (CE$ν$NS) offers valuable sensitivity to physics beyond the Standard Model. The Ricochet experiment will use cryogenic solid-state detectors to perform a precision measurement of the CE$ν$NS spectrum induced by the high neutrino flux from the Institut Laue-Langevin nuclear reactor. The experiment will employ an array of detectors, each with a mass of $\sim$30 g and a targeted energy threshold of 50 eV. Nine of these detectors (the "Q-Array") will be based on a novel Transition-Edge Sensor (TES) readout style, in which the TES devices are thermally coupled to the absorber using a gold wire bond. We present initial characterization of a Q-Array-style detector using a 1 gram silicon absorber, obtaining a baseline root-mean-square resolution of less than 40 eV.

physics.ins-det↗

arXiv2023

Measurement of the $2νββ$ decay rate and spectral shape of $^{100}$Mo from the CUPID-Mo experiment

Neutrinoless double beta decay ($0νββ$) is a yet unobserved nuclear process which would demonstrate Lepton Number violation, a clear evidence of beyond Standard Model physics. The process two neutrino double beta decay ($2νββ)$ is allowed by the Standard Model and has been measured in numerous experiments. In this letter, we report a measurement of $2νββ$ decay half-life of $^{100}$Mo to the ground state of $^{100}$Ru of $(7.07~\pm~0.02~\text{(stat.)}~\pm~0.11~\text{(syst.)})~\times~10^{18}$~yr by the CUPID-Mo experiment. With a relative precision of $\pm~1.6$ \% this is the most precise measurement to date of a $2νββ$ decay rate in $^{100}$Mo. In addition, we constrain higher-order corrections to the spectral shape which provides complementary nuclear structure information. We report a novel measurement of the shape factor $ξ_{3,1}=0.45~\pm 0.03~\text{(stat.)} \ \pm 0.05 \ \text{(syst.)}$, which is compared to theoretical predictions for different nuclear models. We also extract the first value for the effective axial vector coupling constant obtained from a spectral shape study of $2νββ$ decay.

nucl-ex↗

arXiv2023

First demonstration of 30 eVee ionization energy resolution with Ricochet germanium cryogenic bolometers

The future Ricochet experiment aims to search for new physics in the electroweak sector by measuring the Coherent Elastic Neutrino-Nucleus Scattering process from reactor antineutrinos with high precision down to the sub-100 eV nuclear recoil energy range. While the Ricochet collaboration is currently building the experimental setup at the reactor site, it is also finalizing the cryogenic detector arrays that will be integrated into the cryostat at the Institut Laue Langevin in early 2024. In this paper, we report on recent progress from the Ge cryogenic detector technology, called the CryoCube. More specifically, we present the first demonstration of a 30~eVee (electron equivalent) baseline ionization resolution (RMS) achieved with an early design of the detector assembly and its dedicated High Electron Mobility Transistor (HEMT) based front-end electronics. This represents an order of magnitude improvement over the best ionization resolutions obtained on similar heat-and-ionization germanium cryogenic detectors from the EDELWEISS and SuperCDMS dark matter experiments, and a factor of three improvement compared to the first fully-cryogenic HEMT-based preamplifier coupled to a CDMS-II germanium detector. Additionally, we discuss the implications of these results in the context of the future Ricochet experiment and its expected background mitigation performance.

astro-ph.IM↗

arXiv2023

The background model of the CUPID-Mo $0νββ$ experiment

CUPID-Mo, located in the Laboratoire Souterrain de Modane (France), was a demonstrator for the next generation $0νββ$ decay experiment, CUPID. It consisted of an array of 20 enriched Li$_{2}$$ ^{100}$MoO$_4$ bolometers and 20 Ge light detectors and has demonstrated that the technology of scintillating bolometers with particle identification capabilities is mature. Furthermore, CUPID-Mo can inform and validate the background prediction for CUPID. In this paper, we present a detailed model of the CUPID-Mo backgrounds. This model is able to describe well the features of the experimental data and enables studies of the $2νββ$ decay and other processes with high precision. We also measure the radio-purity of the Li$_{2}$$^{100}$MoO$_4$ crystals which are found to be sufficient for the CUPID goals. Finally, we also obtain a background index in the region of interest of 3.7$^{+0.9}_{-0.8}$(stat)$^{+1.5}_{-0.7}$(syst)$\times10^{-3}$counts/$Δ$E$_{FWHM}$/mol$_{iso}$/yr, the lowest in a bolometric $0νββ$ decay experiment.

hep-ex↗

arXiv2023

Tagging and localisation of ionizing events using NbSi transition edge phonon sensors for Dark Matter searches

In the context of direct searches of sub-GeV Dark Matter particles with germanium detectors, the EDELWEISS collaboration has tested a new technique to tag ionizing events using NbSi transition edge athermal phonon sensors. The emission of the athermal phonons generated by the Neganov-Trofimov-Luke effect associated with the drift of electrons and holes through the detectors is used to tag ionization events generated in specific parts of the detector localized in front of the NbSi sensor and to reject by more than a factor 5 (at 90% C.L.) the background from heat-only events that dominates the spectrum above 3 keV. This method is able to improve by a factor 2.8 the previous limit on spin-independent interactions of 1 GeV/c2 WIMPs obtained with the same detector and data set but without this tagging technique.

physics.ins-det↗

arXiv2022

Final results on the $0νββ$ decay half-life limit of $^{100}$Mo from the CUPID-Mo experiment

The CUPID-Mo experiment to search for 0$νββ$ decay in $^{100}$Mo has been recently completed after about 1.5 years of operation at Laboratoire Souterrain de Modane (France). It served as a demonstrator for CUPID, a next generation 0$νββ$ decay experiment. CUPID-Mo was comprised of 20 enriched Li$_2$$^{100}$MoO$_4$ scintillating calorimeters, each with a mass of $\sim$ 0.2 kg, operated at $\sim$20 mK. We present here the final analysis with the full exposure of CUPID-Mo ($^{100}$Mo exposure of 1.47 kg$\times$yr) used to search for lepton number violation via 0$νββ$ decay. We report on various analysis improvements since the previous result on a subset of data, reprocessing all data with these new techniques. We observe zero events in the region of interest and set a new limit on the $^{100}$Mo 0$νββ$ decay half-life of $T^{0ν}_{1/2} > 1.8 \times 10^{24}$ year (stat.+syst.) at 90% CI. Under the light Majorana neutrino exchange mechanism this corresponds to an effective Majorana neutrino mass of $\left < (0.28$--$0.49)$ eV, dependent upon the nuclear matrix element utilized.

nucl-ex↗

arXiv2022

Search for sub-GeV Dark Matter via Migdal effect with an EDELWEISS germanium detector with NbSi TES sensors

The EDELWEISS collaboration reports on the search for Dark Matter (DM) particle interactions via Migdal effect with masses between $32$ MeV$\cdot$c$^{-2}$ to $2$ GeV$\cdot$c$^{-2}$ using a $200$ g cryogenic Ge detector sensitive to simultaneously heat and ionization signals and operated underground at the Laboratoire Souterrain de Modane in France. The phonon signal was read out using a Transition Edge Sensor made of a NbSi thin film. The detector was biased at $66$ V in order to benefit from the Neganov-Trofimov-Luke amplification and resulting in a resolution on the energy of electron recoils of $4.46$ eV$_{ee}$ (RMS) and an analysis threshold of $30$ eV$_{ee}$. The sensitivity is limited by a dominant background not associated to charge creation in the detector. The search constrains a new region of parameter space for cross-sections down to $10^{-29}$ cm$^2$ and masses between $32$ and $100$ MeV$\cdot$c$^{-2}$. The achieved low threshold with the NbSi sensor shows the relevance of its use for athermal-phonon sensitive devices for low-mass DM searches.

astro-ph.GA↗

arXiv2022

Fast neutron background characterization of the future Ricochet experiment at the ILL research nuclear reactor

The future Ricochet experiment aims at searching for new physics in the electroweak sector by providing a high precision measurement of the Coherent Elastic Neutrino-Nucleus Scattering (CENNS) process down to the sub-100 eV nuclear recoil energy range. The experiment will deploy a kg-scale low-energy-threshold detector array combining Ge and Zn target crystals 8.8 meters away from the 58 MW research nuclear reactor core of the Institut Laue Langevin (ILL) in Grenoble, France. Currently, the Ricochet collaboration is characterizing the backgrounds at its future experimental site in order to optimize the experiment's shielding design. The most threatening background component, which cannot be actively rejected by particle identification, consists of keV-scale neutron-induced nuclear recoils. These initial fast neutrons are generated by the reactor core and surrounding experiments (reactogenics), and by the cosmic rays producing primary neutrons and muon-induced neutrons in the surrounding materials. In this paper, we present the Ricochet neutron background characterization using $^3$He proportional counters which exhibit a high sensitivity to thermal, epithermal and fast neutrons. We compare these measurements to the Ricochet Geant4 simulations to validate our reactogenic and cosmogenic neutron background estimations. Eventually, we present our estimated neutron background for the future Ricochet experiment and the resulting CENNS detection significance.

astro-ph.IM↗

arXiv2022

New measurement of double beta decays of $^{100}$Mo to excited states of $^{100}$Ru with the CUPID-Mo experiment

The CUPID-Mo experiment, located at Laboratoire Souterrain de Modane (France), was a demonstrator experiment for CUPID. It consisted of an array of 20 Li$_2^{100}$MoO$_4$ (LMO) calorimeters each equipped with a Ge light detector (LD) for particle identification. In this work, we present the result of a search for two-neutrino and neutrinoless double beta decays of $^{100}$Mo to the first 0$^+$ and $2^+$ excited states of $^{100}$Ru using the full CUPID-Mo exposure (2.71 kg$\times$yr of LMO). We measure the half-life of $2νββ$ decay to the $0^{+}_1$ state as $T_{1/2}^{2ν\rightarrow 0_1^+}=7.5\pm 0.8 \ \text{(stat.)} \ ^{+ 0.4}_{-0.3} \ \text{(syst.)} )\times 10^{20} \ \mathrm{yr}$. The bolometric technique enables measurement of the electron energies as well as the gamma rays from nuclear de-excitation and this allows us to set new limits on the two-neutrino decay to the $2_1^+$ state of $T^{2ν\rightarrow 2_1^+}_{1/2}>4.4\times 10^{21} \ \mathrm{yr} \ \text{(90 % c.i.)}$ and on the neutrinoless modes of $T_{1/2}^{0ν\rightarrow 2_1^+}>2.1\times10^{23} \ \mathrm{yr}\ \text{(90 % c.i.)}$, $T_{1/2}^{0ν\rightarrow 0_1^+}>1.2\times10^{23} \ \mathrm{yr}\ \text{(90 % c.i.)}$. Information on the electrons spectral shape is obtained which allows us to make the first comparison of the single state (SSD) and higher state (HSD) $2νββ$ decay models for the $0_1^+$ excited state of $^{100}$Ru.

nucl-ex↗

arXiv2022

First results of the nuGeN experiment on coherent elastic neutrino-nucleus scattering

The nuGeN experiment is aimed to investigate neutrino properties using antineutrinos from the reactor of the Kalinin Nuclear Power Plant. The experimental setup is located at about 11 meters from the center of the 3.1 GWth reactor core. Scattering of the antineutrinos from the reactor is detected with low energy threshold high purity germanium detector. Passive and active shieldings are used to suppress all kinds of backgrounds coming from surrounding materials and cosmic radiation. The description of the experimental setup together with the first results is presented. The data taken in regimes with reactor ON (94.50 days) and reactor OFF (47.09 days) have been compared. No significant difference between spectra of two data sets is observed, i.e. no positive signals for coherent elastic neutrino-nucleus scattering are detected. Under Standard Model assumptions about coherent neutrino scattering an upper limit on a quenching parameter k < 0.26 (90 \% C.L.) in germanium has been set.

nucl-ex↗

arXiv2022

Low-mass Dark Matter searches with EDELWEISS

The EDELWEISS collaboration searches for light Dark Matter (DM) particles using germanium detectors equipped with a charge and phonon signal readout. Using the Neganov-Trofimov-Luke effect, an rms resolution of 0.53 electron-hole pair was obtained on a massive (33.4 g) Ge detector operated underground at the Laboratoire Souterrain de Modane. This record sensitivity made possible a search for Dark Photon DM down to 1 eV/c2 and to DM-electron interactions below 1 MeV/c2. This demonstrates for the first time the high relevance of cryogenic Ge detectors in searches at low thresholds and is an important step of the development of Ge detectors with improved performance in the context of the EDELWEISS-SubGeV program.

physics.ins-det↗

arXiv2022

First germanium-based constraints on sub-MeV Dark Matter with the EDELWEISS experiment

The EDELWEISS collaboration has performed a search for Dark Matter (DM) particles interacting with electrons using a 33.4 g Ge cryogenic detector operated underground at the LSM. A charge resolution of 0.53 electron-hole pairs (RMS) has been achieved using the Neganov-Trofimov-Luke amplification with a bias of 78 V. We set the first Ge-based constraints on sub-MeV/c$^{2}$ DM particles interacting with electrons, as well as on dark photons down to 1 eV/c$^2$. These are competitive with other searches. In particular, new limits are set on the kinetic mixing of dark photon DM in a so far unconstrained parameter space region in the 6 to 9 eV/c$^2$ mass range. These results demonstrate the high relevance of cryogenic Ge detectors for the search of DM interactions producing eV-scale electron signals.

astro-ph.GA↗

arXiv2022

High impedance TES bolometers for EDELWEISS

The EDELWEISS collaboration aims for direct detection of light dark matter using germanium cryogenic detectors with low threshold phonon sensor technologies and efficient charge readout designs. We describe here the development of Ge bolometers equipped with high impedance thermistors based on a NbxSi1-x TES alloy. High aspect ratio spiral designs allow the TES impedance to match with JFET or HEMT front-end amplifiers. We detail the behavior of the superconducting transition properties of these sensors and the detector optimization in terms of sensitivity to out-of-equilibrium phonons. We report preliminary results of a 200 g Ge detector that was calibrated using 71Ge activation by neutrons at the LSM underground laboratory.

physics.ins-det↗