The detectors are made from germanium with the fraction of the 76Ge isotope enriched from 7.8% to about 87%. Since the source and the detector of Ovßß decay are identical in this calorimetric ...approach, the detection efficiency is high. A rock overburden of about 3,500 m water equivalent removes the hadronic components of cosmic ray showers and reduces the muon flux at the experiment by six orders of magnitude, to 1.2 muons m-2 h-1.
Neutrinoless double electron capture is a process that, if detected, would give evidence of lepton number violation and the Majorana nature of neutrinos. A search for neutrinoless double electron ...capture of
36
Ar has been performed with germanium detectors installed in liquid argon using data from Phase I of the GERmanium Detector Array (
Gerda
) experiment at the Gran Sasso Laboratory of INFN, Italy. No signal was observed and an experimental lower limit on the half-life of the radiative neutrinoless double electron capture of
36
Ar was established:
T
1
/
2
>
3.6
×
10
21
years at 90% CI.
The GERDA experiment searches for the lepton-number-violating neutrinoless double-β decay of ^{76}Ge (^{76}Ge→^{76}Se+2e^{-}) operating bare Ge diodes with an enriched ^{76}Ge fraction in liquid ...argon. The exposure for broad-energy germanium type (BEGe) detectors is increased threefold with respect to our previous data release. The BEGe detectors feature an excellent background suppression from the analysis of the time profile of the detector signals. In the analysis window a background level of 1.0_{-0.4}^{+0.6}×10^{-3} counts/(keV kg yr) has been achieved; if normalized to the energy resolution this is the lowest ever achieved in any 0νββ experiment. No signal is observed and a new 90% C.L. lower limit for the half-life of 8.0×10^{25} yr is placed when combining with our previous data. The expected median sensitivity assuming no signal is 5.8×10^{25} yr.
The CONUS experiment studies coherent elastic neutrino nucleus scattering in four 1 kg germanium spectrometers. Low ionization energy thresholds of 210 eV were achieved. The detectors were operated ...inside an optimized shield at the Brokdorf nuclear power plant which provided a reactor antineutrino flux of up to \(2.3\cdot10^{13}\) cm\(^{-2}\)s\(^{-1}\). In the final phase of data collection at this site, the constraints on the neutrino interaction rate were improved by an order of magnitude as compared to the previous CONUS analysis. The new limit of less than 0.34 signal events kg\(^{-1}\)d\(^{-1}\) is within a factor 2 of the rate predicted by the Standard Model.
We report first constraints on neutrino electromagnetic properties from neutrino-electron scattering using data obtained from the CONUS germanium detectors, i.e. an upper limit on the effective ...neutrino magnetic moment and an upper limit on the effective neutrino millicharge. The electron antineutrinos are emitted from the 3.9 GW\(_\mathrm{th}\) reactor core of the Brokdorf nuclear power plant in Germany. The CONUS low background detectors are positioned at 17.1 m distance from the reactor core center. The analyzed data set includes 689.1 kg\(\cdot\)d collected during reactor ON periods and 131.0 kg\(\cdot\)d collected during reactor OFF periods in the energy range of 2 to 8 keV\(_{ee}\). With the current statistics, we are able to determine an upper limit on the effective neutrino magnetic moment \(\mu_\nu < 7.5\cdot10^{-11}\,\mu_B\) at 90% confidence level. From this first magnetic moment limit we can derive an upper bound on the neutrino millicharge of \(\vert q_{\nu}\vert < 3.3\cdot10^{-12}\,e_0\).
This article reports the measurement of the ionization quenching factor in germanium for nuclear recoil energies between 0.4 and 6.3 keV\(_{nr}\). Precise knowledge of this factor in this energy ...range is relevant for coherent elastic neutrino-nucleus scattering and low mass dark matter searches with germanium-based detectors. Nuclear recoils were produced in a thin high-purity germanium target with a very low energy threshold via irradiation with monoenergetic neutron beams. The energy dependence of the ionization quenching factor was directly measured via kinematically constrained coincidences with surrounding liquid scintillator based neutron detectors. The systematic uncertainties of the measurements are discussed in detail. With measured quenching factors between 0.16 and 0.23 in the 0.4, 6.3 keV\(_{nr}\) energy range, the data are compatible with the Lindhard theory with a parameter \(k\) of 0.162 \(\pm\) 0.004 (stat+sys).
The measurements of coherent elastic neutrino-nucleus scattering (CE\(\nu\)NS) experiments have opened up the possibility to constrain neutrino physics beyond the standard model of elementary ...particle physics. Furthermore, by considering neutrino-electron scattering in the keV-energy region, it is possible to set additional limits on new physics processes. Here, we present constraints that are derived from CONUS germanium data on beyond the standard model (BSM) processes like tensor and vector non-standard interactions (NSIs) in the neutrino-quark sector, as well as light vector and scalar mediators. Thanks to the realized low background levels in the CONUS experiment at ionization energies below 1 keV, we are able to set the world's best limits on tensor NSIs from CE\(\nu\)NS and constrain the scale of corresponding new physics to lie above 360 GeV. For vector NSIs, the derived limits strongly depend on the assumed ionization quenching factor within the detector material, since small quenching factors largely suppress potential signals for both, the expected standard model CE\(\nu\)NS process and the vector NSIs. Furthermore, competitive limits on scalar and vector mediators are obtained from the CE\(\nu\)NS channel at reactor-site which allow to probe coupling constants as low as \(5\cdot10^{-5}\) of low mediator masses, assuming the currently favored quenching factor regime. The consideration of neutrino-electron scatterings allows to set even stronger constraints for mediator masses below \(\sim1\) MeV and \(\sim 10\) MeV for scalar and vector mediators, respectively.
The CONUS experiment is searching for coherent elastic neutrino nucleus scattering of reactor anti-neutrinos with four low energy threshold point-contact high-purity germanium spectrometers. An ...excellent background suppression within the region of interest below 1keV (ionization energy) is absolutely necessary to enable a signal detection. The collected data also make it possible to set limits on various models regarding beyond the standard model physics. These analyses benefit as well from the low background level of ~10d\(^{-1}\)kg\(^{-1}\)below 1keV and at higher energies. The low background level is achieved by employing a compact shell-like shield, that was adapted to the most relevant background sources at the shallow depth location of the experiment: environmental gamma-radiation and muon-induced secondaries. Overall, the compact CONUS shield including the active anti-coincidence muon-veto reduces the background by more than four orders of magnitude. The remaining background is described with validated Monte Carlo simulations which include the detector response. It is the first time that a full background decomposition in germanium operated at reactor-site has been achieved. Next to remaining muon-induced background, \(^{210}\)Pb within the shield and cryostat end caps, cosmogenic activation and air-borne radon are the most relevant background sources. The reactor-correlated background is negligible within the shield. The validated background model together with the parameterization of the noise are used as input to the likelihood analyses of the various physics cases.
We report the best limit on coherent elastic scattering of electron antineutrinos emitted from a nuclear reactor off germanium nuclei. The measurement was performed with the CONUS detectors ...positioned at 17.1m from the 3.9GWth reactor core of the nuclear power plant in Brokdorf, Germany. The antineutrino energies of less than 10 MeV assure interactions in the fully coherent regime. The analyzed dataset includes 248.7 kgd with the reactor turned on and background data of 58.8 kgd with the reactor off. With a quenching parameter of k = 0.18 for germanium, we determined an upper limit on the number of neutrino events of 85 in the region of interest at 90% confidence level. This new CONUS dataset disfavors quenching parameters above k = 0.27, under the assumption of standard-model-like coherent scattering of the reactor antineutrinos.
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