Probing Resonant Leptogenesis at the LHC

TL;DR

This paper investigates how the Large Hadron Collider (LHC) can directly test resonant leptogenesis models that explain the matter-antimatter asymmetry of the universe through specific collider signatures involving a new Z' gauge boson and right-handed neutrinos.

Contribution

It proposes a method to probe resonant leptogenesis at the LHC by analyzing like-sign dilepton events from Z' decays, linking collider signals to the matter-antimatter asymmetry.

Findings

LHC can test CP asymmetry  \u2248 0.22 with 300 fb^{-1} data.

An excess of antileptons is predicted if leptogenesis is responsible for baryon asymmetry.

Identifies parameter space where direct collider tests are feasible.

Abstract

We explore direct collider probes of the resonant leptogenesis mechanism for the origin of matter. We work in the context of theories where the Standard Model is extended to include an additional gauged U(1) symmetry broken at the TeV scale, and where the light neutrinos obtain mass through a Type I seesaw at this scale. The CP asymmetry that generates the observed matter-antimatter asymmetry manifests itself in a difference between the number of positive and negative like-sign dileptons N(\ell^+\ell^+)-N(\ell^-\ell^-) that arise in the decay of the new Z' gauge boson to two right-handed neutrinos N, and their subsequent decay to leptons. The relatively low efficiency of resonant leptogenesis in this class of models implies that the CP asymmetry, \epsilon, is required to be sizable, i.e. of order one. In particular, from the sign of the baryon asymmetry of the Universe, \emph{an excess of antileptons is predicted}. We identify the domains in M_{Z'}--M_N space where such a direct test is possible and find that with 300~fb^{-1} of data and no excess found, the LHC can set the $2\sigma$ exclusion limit \epsilon \lesssim 0.22.