Top quark physics in the Vector Color-Octet Model

TL;DR

This paper investigates the vector color-octet model's ability to explain the top quark forward-backward asymmetry observed at Tevatron, while satisfying constraints from LHC data and other collider searches.

Contribution

It provides a comprehensive analysis of the parameter space of the vector color-octet model, including FC and FV couplings, and predicts collider signatures consistent with observed data.

Findings

The model can explain the afbt anomaly without conflicting with collider constraints.

Single top production is more sensitive to model couplings than top-pair production.

Exclusion contours are established for FV couplings based on recent collider data.

Abstract

We study and constrain the parameter space of the vector color-octet model from observed data at Tevatron by studying top quark pair production and associated observables afbt and spin-correlation. In particular we study invariant mass and rapidity dependence of afbt at Tevatron. In addition to FC couplings we extend our study to include FV coupling involving first & third generation quarks for both these processes. In order to ensure that we remain within the constraints imposed by LHC data, we analyze the charge asymmetry, p_T spectrum & invariant mass in t\bar t production data at LHC. The constraints from dijet resonance searches performed by LHC are also considered. We also explore the contribution of this model to single top quark production mediated by charged & neutral color-octet vector bosons. FV couplings introduced then induce same-sign top-pair production process which is analyzed for both hadron colliders. We have incorporated effect of finite decay width of color octets on these processes. We find that it is possible to explain the observed afbt anomaly in color-octet vector model without transgressing production cross sections of all these processes both through FC and FV couplings at Tevatron. We predict best point sets in model parameter space for specific choices of color-octet masses corresponding to chi^2_min evaluated using mttb and dyy spectrum of afbt from observed data set at Tevatron (8.7 fb-1). We find that single top quark production is more sensitive to FC and FV couplings in comparison to top-pair production. We provide 95% exclusion contours on the plane of FV chiral couplings from recent data at Tevatron, CMS and ATLAS corresponding to nonobservability of large same-sign dilepton events. The four observed point sets are consistent with the cross section, charge asymmetry and spin-correlation measurements for t\bar t production & dijet searches at LHC.