# 17th International Conference on Topics in Astroparticle and Underground Physics (TAUP 2021)

26 August 2021 to 3 September 2021

## Low Threshold Germanium Detectors for Neutrino-Nucleus Elastic Scattering and the Studies of its Quantum-Mechanical Coherency Effects

30 Aug 2021, 18:00
1h 30m
Poster Neutrino physics and astrophysics

### Speaker

Vivek Sharma (Institute of Physics, Academia Sinica, Taipei, Taiwan)

### Description

Neutrino Nucleus Elastic Scattering ($\nu A_{el}$) offers a unique laboratory to study Quantum Mechanical superpositions in electroweak interactions, towards which several experimental programs are being actively pursued. In the TEXONO experiment, we are currently focused to measure the $\nu A_{el}$ cross-section for the reactor neutrinos (E$_\nu$ <10 MeV) at Kuo-Sheng Reactor Neutrino Laboratory (KSNL) ${[1]}$. We are using the state-of-art point contact Germanium detector technology with the advance pulse-tube electro-cool mechanism to probe this small nuclear recoil process. We will report our status and plan for achieving low threshold & background with Germanium detectors at KSNL. We also identified a new parameter ($\alpha$) to describe the degree of coherency in $\nu A_{el}$, which depends on incoming neutrino energy, detector threshold, and target nucleus $[2]$. The description of $\nu A_{el}$ process in terms of $\alpha$ is complementary to the conventional descriptions with nuclear form factors based on the many-body physics in the nucleon-nucleus interplay. We derive three possible formulations to measure $\alpha$, based on (a) Nuclear Physics (b) Quantum Mechanical description and (c) Data driven description $[3]$. We found that coherency is mostly complete ($\alpha$ >95%) for $\nu A_{el}$ with reactor and solar neutrinos for Xe/CsI, Ge and Ar targets, whereas coherency is only partial for DAR-$\pi$ and weak for atmospheric neutrinos. Accordingly, studies of $\nu A_{el}$ with different neutrino sources provide complementary information and cover the transitions from completely coherent to decoherent states. We also exclude the complete coherency and decoherency conditions for COHERENT (CsI) data and project the sensitivity for reactor $\nu A_{el}$ with Ge detector.

1. Research program towards observation of neutrino-nucleus coherent
scattering., H. T. Wong et al., J. Conf. Ser. 39, 266 (2006).
2. Coherency in neutrino-nucleus elastic scattering., S. Kerman et al., Phys. Rev. D93, 113006 (2016).
3. Studies of quantum-mechanical coherency effects in neutrino-nucleus elastic scattering. V. Sharma et al., Phys. Rev. D 103, 092002 (2021).
Reference to paper (DOI or arXiv) https://doi.org/10.1103/PHYSREVD.103.092002

### Primary authors

Vivek Sharma (Institute of Physics, Academia Sinica, Taipei, Taiwan) Prof. Henry Tsz-King Wong (Institute of Physics, Academia Sinica)

### Presentation Materials

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