Sigma to p mu+ mu-: Standard Model or New Particle?

TL;DR

This paper re-examines the Sigma to p mu+ mu- decay, showing it can be explained within the Standard Model or by a new light pseudoscalar Higgs boson in the NMSSM, addressing HyperCP's observations.

Contribution

It demonstrates that the decay mode can be explained by SM long-distance effects or a new light Higgs boson, providing a specific NMSSM example consistent with experimental constraints.

Findings

Decay rate consistent with HyperCP measurement within SM

Light pseudoscalar Higgs in NMSSM can explain the observations

Conditions for new particle interpretation are explicitly identified

Abstract

The HyperCP collaboration observed three events for the decay Sigma to p mu+ mu-. They suggested that new physics may be required to understand the implied decay rate and the observed dimuon invariant mass distribution. Motivated by this result, we re-examine this mode. First within the standard model, and then assuming there is a new particle. Within the SM we find that this mode is long-distance dominated and its rate falls within the range suggested by the HyperCP measurement. We then examine the conditions under which the observation is consistent with a light Higgs boson and find an explicit example that satisfies all the constraints: the light pseudoscalar Higgs boson in the next-to-minimal supersymmetric standard model (NMSSM).