Abstract
The NUCLEUS experiment aims for the detection of coherent elastic neutrino-nucleus scattering at a nuclear power reactor with gram-scale, ultra-low-threshold cryogenic detectors. This technology leads to a miniaturization of neutrino detectors and allows to probe physics beyond the Standard Model of particle physics. A 0.5 g NUCLEUS prototype detector, operated above ground in 2017, reached an energy threshold for nuclear recoils of below 20 eV. This sensitivity is achieved with tungsten transition edge sensors which are operating at temperatures of 15 mK and are mainly sensitive to non-thermal phonons. These small recoil energies become accessible for the first time with this technology, which allows collecting large-statistics neutrino event samples with a moderate detector mass. A first-phase cryogenic detector array with a total mass of 10 g enables a 5-sigma observation of coherent scattering within several weeks. We identified a suitable experimental site at the Chooz Nuclear Power Plant and performed muon and neutron background measurements there. The operation of a NUCLEUS cryogenic detector array at such a site requires highly efficient background suppression. NUCLEUS plans to use an innovative technique consisting of separate cryogenic anticoincidence detectors against surface backgrounds and penetrating (gamma, neutron) radiation. We present first results from prototypes of these veto detectors and their operation in coincidence with a NUCLEUS target detector.
Highlights
Since its proposal in 1974 [1], coherent elastic neutrino-nucleus scattering (CEνNS ) has attracted growing attention in particle physics
With a typical reactor neutrino energy of around 3 MeV, the interaction cross section and observable nuclear recoil energies are around two orders of magnitude lower compared to a stopped-pion source
The NUCLEUS target detectors are evolved from technology used in the CRESST direct dark matter search experiment [13,14]
Summary
Since its proposal in 1974 [1], coherent elastic neutrino-nucleus scattering (CEνNS ) has attracted growing attention in particle physics. It was first observed in 2017 by the COHERENT collaboration [2] using the neutrino emission of the Spallation Neutron Source (SNS) at the Oak Ridge National Laboratory. With a typical reactor neutrino energy of around 3 MeV, the interaction cross section and observable nuclear recoil energies (which both scale with Eν2) are around two orders of magnitude lower compared to a stopped-pion source. While the lower recoil energies have to be detected with a more sensitive apparatus, the available neutrino flux near a power reactor can more than overcompensate the lower cross section, allowing large-statistics experiments with a small target mass. Various scenarios of physics beyond the Standard Model can be probed in such an experiment (see [10,11,12] and references therein)
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