CP violation in top quark decay via heavy Majorana neutrinos at the LHC

TL;DR

This paper explores the potential to observe CP violation in top quark decays caused by heavy Majorana neutrinos at the LHC, which could signal new physics beyond the standard model.

Contribution

It analyzes the CP asymmetry in top quark pair production and decay mediated by nearly-degenerate Majorana neutrinos within a low-scale seesaw framework.

Findings

CP asymmetry can be significant with nearly-degenerate Majorana neutrinos.

The CP asymmetry is independent of neutrino mass in the 10-80 GeV range.

Observation of CP violation would indicate physics beyond the standard model.

Abstract

The tiny neutrino masses can be explained naturally by extending the standard model with right-handed Majorana neutrinos in low-scale seesaw mechanism, and the CP violation effect induced by Majorana phase is interesting and worth studying at colliders. In this paper, we investigate the prospects for measuring CP violation in top quark pair production and rare decay via Majorana neutrinos at the LHC. The CP asymmetry stems from the significant interference of contributions from two different Majorana neutrinos and can be appreciable when the two neutrino masses are nearly-degenerate. It is found that in the Majorana neutrino mass range of 10 GeV < mn < 80 GeV, the CP asymmetry is independent of the Majorana neutrino mass at the LHC. Any possible new observation of CP violation will be the clear evidence of new physics beyond the standard model.