Research program towards observation of neutrino-nucleus coherent scattering

Abstract

Abstract. The article describes the research program towards an experiment to observe coherent scattering between neutrinos and the nucleus at the power reactor. The motivations of studying this process are surveyed. In particular, a threshold of 100-200 eV has been achieved with an ultra-low-energy germanium detector prototype. This detection capability at low energy can also be adapted for searches of Cold Dark Matter in the low-mass region as well as to enhance the sensitivities in the study of neutrino magnetic moments. Neutrino coherent scattering with the nucleus[1]is a fundamental neutrino interaction which has never been experimentally observed. The Standard Model cross section for this process is given by:where m N , N and Z are the mass, neutron number and atomic number of the nuclei, respectively, E ν is the incident neutrino energy and T N is the measure-able recoil energy of the nucleus. This formula is applicable for E ν < 50 MeV where the momentum transfer (Q 2 ) is small such that Q 2 R 2 < 1, where R is the nuclear size. Although the cross-section is relatively large due to the ∼N 2 enhancement by coherence, the small kinetic energy from nuclear recoils poses severe experimental challenges both to the detector sensitivity and to background control. Various detector techniques have been considered[2] to meet these challenges. Measurement of the coherent scattering cross-section would provide a sensitive test to the Standard Model [3], probing the weak nuclear charge and radiative corrections due to possible new physics above the weak scale. The coherent interaction plays important role in astrophysical processes where the neutrino-electron scatterings are suppressed due to Fermi gas degeneracy.