Top quark forward-backward asymmetry andW′bosons

Abstract

The top quark forward-backward asymmetry measured at the Fermilab Tevatron collider deviates from the standard model prediction. A W ′ boson model is described, where the coupling W ′ -t-d is fixed by the tt forward-backward asymmetry and total cross section at the Tevatron. We show that such a W ′ boson would be produced in association with a top quark at the CERN Large Hadron Collider (LHC), thus inducing additional tt+j events. We use measurements of tt+n-jet production from the LHC to constrain the allowed W ′ -t-d couplings as a function of W ′ boson mass. We find that this W ′ model is constrained at the 95% C.L. using 0.7 fb −1 of data from the LHC, and could be fully excluded with 5 fb −1 of data.

ChargedZ′to conciliate the apparent disagreement betweentt¯Tevatron forward-backward asymmetry and LHC charge asymmetry

“…[43] as a rough estimation of the t " tj production at the LHC in our model. We repeated the simulations for values of the Z 0 width increased by three different factors and searched again for the allowed parameter space in these cases.…”

Interpretations and implications of the top quark rapidity asymmetriesAFBtandAFBℓ

“…The minimal version of the Z ′ model implies a large rate for same-sign top quark pair production at the LHC, not supported by data [7,85,86]. The W ′ model is highly constrained by data on the tt plus jets final state at the LHC [34,35,84].…”

“…3. However, a complete analysis must take into account interference between tt + j in the SM and the W ′ model [35,37] and a large enhancement from NLO QCD corrections (K−factor ∼ 1.3 − 1.5 [36]) . We defer it for future study.…”

“…These models usually postulate the existence of new states, whether in the direct-channel coupling to tt, or exchanged in a cross-channel and coupling the top quark to first-and/or second-generation quarks. Examples include flavor-changing Z ′ , W ′ [25][26][27][28][29][30][31][32][33][34][35][36][37] and axigluon G ′ models, among others [37,.…”

What the top asymmetries tell us about single top production and Higgs decays

“…If confirmed, this discrepancy might suggest the presence of NP affecting the top quark pair production, and several models have been proposed. These models fall into two main categories; s-channel exchange of vector mediators with axial couplings [17] or t-channel exchange of flavor-violating mediators, either scalars [18] or vectors [19]. In this paper we focus on the possibility to explain and relate both these experimental anomalies with the help of an extra scalar doublet in addition to the SM.…”