Measurement of two-neutrino double electron capture half-life of ¹²⁴Xe with PandaX-4T

2024/11/21 by PandaX Collaboration, Zihao Bo, Wei Chen +197 · 1 citation
Physics and Astronomy · #Neutrino Physics Research #Dark Matter and Cosmic Phenomena #Astrophysics and Cosmic Phenomena

paper · pdf · doi:10.48550/arxiv.2411.14355

Abstract

Detailed studies of two-neutrino double electron capture (2νDEC) is a crucial step towards searching for the neutrino-less mode to explore the Majorana nature of neutrinos. We have measured precisely the half-life of the 2νDEC process in ¹²⁴Xe, utilizing a total exposure of 1.73 tonne⋅year from the commissioning run and the first science run of the PandaX-4T experiment. A time-dependent background model in the O(10 keV) energy is constructed for the first time in PandaX-4T data. With an unbinned maximum likelihood fit, we determine the half-life of the 2νDEC process to be (1.03±0.15_{\rm stat}±0.08_{\rm sys})× 10²² yr. Furthermore, we have evaluated the branching ratio for both electrons captured from the K shell (KK) to be (65±5)%, which aligns with the ¹²⁴Xe nuclear model calculations within 1.8 σ.

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