CP violation in $\Sigma^+\to p\ell^+\ell^-$ within the standard model and beyond

TL;DR

This paper investigates the potential for observing $CP$ violation in the rare hyperon decay $\, ext{Sigma}^+ o p \, ext{leptons}^+ \, ext{leptons}^-$, highlighting the possibility of large asymmetries detectable by LHCb.

Contribution

It analyzes $CP$ violation in hyperon decays within and beyond the standard model, emphasizing the role of long-distance effects and potential new physics contributions.

Findings

Decay rate asymmetry could be as high as tens of percent.

Large $CP$ violation effects are possible due to interference with new physics.

LHCb can potentially observe these asymmetries in upcoming measurements.

Abstract

The LHCb collaboration has recently observed the rare hyperon decay $\Sigma^+\to p\mu^+\mu^-$. It can also measure the corresponding antihyperon channel with comparable precision and is thus in a position to extract information on $CP$ violation in this mode. Interestingly, the long-distance contributions that dominate it within the standard model provide large absorptive phases that could drive substantial $CP$ violation through interference with potential new-physics contributions. Here we explore this possibility, finding that the decay rate asymmetry is currently allowed to be as high as tens of percent, which can be probed by LHCb in the near future. We additionally consider the same with regard to the dielectron mode $\Sigma^+\to pe^+e^-$ as well as the related radiative one $\Sigma^+\to p\gamma$.