First Search for Lorentz and CPT Violation in Double Beta Decay with EXO-200

TL;DR

This paper reports the first experimental search for Lorentz and CPT violation effects in double beta decay using the EXO-200 detector, setting new limits on SME coefficients with no observed violations.

Contribution

It presents the first experimental constraints on Lorentz and CPT violation in double beta decay via the SME framework using the EXO-200 data.

Findings

No significant spectral modification detected.

Set a new limit on the SME coefficient $ar{a}_{ ext{of}}^{(3)}$.

Established constraints within 90% confidence level.

Abstract

This proceedings contribution reports the first experimental search for Lorentz- and CPT-violating signals specifically studying the effect of the Standard-Model Extension (SME) oscillation-free momentum-independent neutrino coupling operator in the double beta decay process. The search has been performed using an exposure of 100 kg yr of $^{136}$Xe with the EXO-200 detector. No significant evidence of the spectral modification due to isotropic Lorentz violation was found. A two-sided limit of $-2.65 \times 10^{-5}$ GeV $<$ $\mathring{a}_{\mathrm{of}}^{(3)}$ $< 7.60 \times 10^{-6}$ GeV (90% C.L.) is placed on the relevant coefficient within the SME.