Exploring invisible neutrino decay at ESSnuSB

TL;DR

This paper investigates the potential of the ESSnuSB experiment to detect and constrain invisible neutrino decay, comparing two baselines and analyzing impacts on CP violation measurements.

Contribution

It provides the first detailed analysis of ESSnuSB's sensitivity to invisible neutrino decay and compares baseline options for decay detection and measurement.

Findings

ESSnuSB can bound the decay parameter at $3\sigma$ for both baselines.

The 360 km baseline yields a slightly better bound than DUNE.

The 540 km baseline has higher potential for discovering decay and precise measurement.

Abstract

We explore invisible neutrino decay in which a heavy active neutrino state decays into a light sterile neutrino state and present a comparative analysis of two baseline options, $540~$km and $360~$km, for the ESSnuSB experimental setup. Our analysis shows that ESSnuSB can put a bound on the decay parameter $\tau_3/m_3 = 2.64~(1.68) \times 10^{-11}~$s/eV for the baseline option of $360~(540)~$km at $3 \sigma$. The expected bound obtained for $360~$km is slightly better than the corresponding one of DUNE for a charged current (CC) analysis. Furthermore, we show that the capability of ESSnuSB to discover decay, and to measure the decay parameter precisely, is better for the baseline option of $540~$km than that of $360~$km. Regarding effects of decay in $\delta_{\rm CP}$ measurements, we find that in general the CP violation discovery potential is better in the presence of decay. The change in CP precision is significant if one assumes decay in data but no decay in theory.