Leptogenesis via the 750 GeV pseudoscalar

TL;DR

This paper explores how a 750 GeV pseudoscalar boson, suggested by collider excesses, could influence early universe cosmology and potentially explain the matter-antimatter asymmetry through induced lepton number violation.

Contribution

It investigates the cosmological implications of the 750 GeV pseudoscalar, linking collider signals to baryogenesis via quantum fluctuations and induced chemical potentials.

Findings

The S field can develop a large vacuum expectation value during inflation.

Operators coupling S to gauge fields induce a chemical potential for baryon and lepton number.

Interactions with right-handed neutrinos can generate a lepton asymmetry.

Abstract

Recently the ATLAS and CMS collaborations have reported evidence of a diphoton excess which may be interpreted as a pseudoscalar boson S with a mass around 750 GeV. To explain the diphoton excess, such a boson is coupled to the Standard Model gauge fields via SFF-dual operators. In this work, we consider the implications of this state for early universe cosmology; in particular, the S field can acquire a large vacuum expectation value due to quantum fluctuations during inflation. During reheating, it then relaxes to its equilibrium value, during which time the same operators introduced to explain the diphoton excess induce a nonzero chemical potential for baryon and lepton number. Interactions such as those involving right-handed neutrinos allow the system to develop a non-zero lepton number, and therefore, this state may also be responsible for the observed cosmological matter-antimatter asymmetry.