Exploring beta decay with light boson emission in the KATRIN experiment

The Karlsruhe Tritium Neutrino (KATRIN) experiment is designed to measure the effective electron antineutrino mass with a sensitivity better than mνc2=0.3 eV (90% C.L.) in a kinematic approach by applying precision electron spectroscopy to the beta decay of molecular tritium. The measurement focuses on the spectral endpoint (E0) region, extending up to tens of eV below E0 ≈ 18.6 keV.

Light neutral pseudoscalars and vector bosons are predicted in many theories beyond the Standard Model (BSM). Constraints on the couplings of such particles to neutrinos or electrons can be derived from cosmological, astrophysical and laboratory observations. With high-statistics beta spectroscopy, KATRIN complements these approaches, as the emission of an additional light state in tritium beta decay introduces characteristic modifications to the observed electron spectrum. We present the computation of these spectra, based on JHEP 01 (2019) 206. Preliminary analysis of the second KATRIN measurement campaign explores the parameter space of boson couplings, offering perspectives for BSM physics.