Nucleon EDM and rare decays of eta mesons

TL;DR

This paper links rare CP-violating eta meson decays to nucleon EDM constraints, deriving stringent upper limits on decay rates based on neutron EDM experimental bounds.

Contribution

It establishes a direct relationship between eta meson decay rates and nucleon EDM, providing new, tighter constraints on decay branching ratios from neutron EDM data.

Findings

Derived upper bounds on eta decay branching ratios: 3.5×10^{-14} and 1.8×10^{-17}.

Connected CP-violating decay processes to nucleon EDM constraints.

Provided a method to translate neutron EDM limits into bounds on rare meson decays.

Abstract

I consider rare CP-violating decay modes $\eta(\eta')\to\pi\pi$ and note that an interaction that leads to such decays would necessarily induce a nucleon electric dipole moment (EDM). The experimental limits for the corresponding branching ratios are quite soft. I relate these decay branching ratios to the value of the induced nucleon EDM and translate the experimental limits on the neutron EDM into much more stringent constraints on these decay rates: $\frac{\Gamma_{\eta\to\pi\pi}}{\Gamma_\eta}\lesssim3.5\times10^{-14}$ and $\frac{\Gamma_{\eta'\to\pi\pi}}{\Gamma_\eta'}\lesssim1.8\times10^{-17}$.