Top quark forward-backward asymmetry in R-parity violating supersymmetry

TL;DR

This paper proposes that bottom squark-mediated top quark pair production within R-parity violating supersymmetry can explain the Tevatron's large top quark forward-backward asymmetry while remaining consistent with other experimental constraints.

Contribution

It introduces a supersymmetric model with bottom squark mediation as a novel explanation for the top quark asymmetry, addressing previous constraints and proposing mechanisms to weaken atomic parity violation limits.

Findings

Model fits top quark asymmetry data well

Proposed diagram weakens atomic parity violation constraints

Scenario avoids flavor-changing neutral current issues with third-generation sparticles

Abstract

The interaction of bottom squark-mediated top quark pair production, occurring in the R-parity violating minimal supersymmetric standard model (MSSM), is proposed as an explanation of the anomalously large $t\bar{t}$ forward-backward asymmetry (FBA) observed at the Tevatron. We find that this model can give a good fit to top quark data, both the inclusive and invariant mass-dependent asymmetries, while remaining consistent (at the 2-$\sigma$ level) with the total and differential production cross-sections. The scenario is challenged by strong constraints from atomic parity violation (APV), but we point out an extra diagram for the effective down quark-Z vertex, involving the same coupling constant as required for the FBA, which tends to weaken the APV constraint, and which can nullify it for reasonable values of the top squark masses and mixing angle. Large contributions to flavor-changing neutral currents can be avoided if only the third generation of sparticles is light.