CP violation in associated production of a charged Higgs boson and a top quark at the LHC

TL;DR

This paper investigates CP violation effects in the production of charged Higgs bosons with top quarks at the LHC, finding asymmetries up to 20% in production and 13% when including decays, within the MSSM framework.

Contribution

It provides a detailed next-to-leading order calculation of CP asymmetries in charged Higgs production and decay at the LHC, highlighting the significance of box graph contributions.

Findings

Production asymmetry ~20% at NLO.

Decay asymmetry can add up to ~13%.

Self energy contributions cancel in certain decay channels.

Abstract

We study effects of CP violation in an associated production of a charged Higgs boson and a top quark at the LHC: $pp \to tH^\pm +X$. We calculate the CP violating asymmetry between the total cross section for $H^+$ and $H^-$ production at next-to-leading order in the MSSM, and perform a detailed numerical analysis. In the production only the asymmetry is of the order of 20%. The asymmetry in the production and any subsequent decay of an on-shell charged Higgs boson is to a good approximation the sum of the asymmetry in the production and the asymmetry in the decay. We consider subsequent decays of $H^\pm $ to $tb$, $\nu_\tau \tau^\pm$ and $Wh^0$. In the case of subsequent $H^\pm \to tb$ decay, the $W^\pm - H^\pm$ self energy contributions from the production and the decay cancel. However, the remaining effect, mainly due to CP violating box graphs with gluino can go up to $\sim 13$%.