New-physics searches in $C\!P$-violating $\eta$ muonic decays

TL;DR

This paper explores the potential to detect $C ext{-}P$ violation in $ ext{eta}$ meson decays involving muons at the REDTOP experiment, using SMEFT to identify a specific operator capable of revealing new physics.

Contribution

It identifies a unique SMEFT operator that could enable observation of $C ext{-}P$ violation in $ ext{eta} o ext{mu}^+ ext{mu}^-$ decays at REDTOP without conflicting with existing bounds.

Findings

A specific SMEFT operator allows $C ext{-}P$ violation detection in $ ext{eta}$ decays.

Detection is feasible at REDTOP with current experimental sensitivity.

The operator evades constraints from neutron EDM and $D^- o ext{mu}ar{ u}$ bounds.

Abstract

In this work we investigate the possibility to observe $C\!P$-violation in $\eta$ decays containing muons at the proposed REDTOP experiment. Employing the SMEFT to parametrize the new-physics $C\!P$-violating effects, we find that a single operator exists for which is possible to observe $C\!P$-violation at REDTOP in $\eta\to\mu^+\mu^-$ decays, while evading bounds from the neutron electric dipole moment and $D^-\to\mu\bar{\nu}$