Vector-like top/bottom-quark partners and Higgs physics at the LHC

摘要

Vector-like quarks (VLQ) that are partners of the heavy top and bottom quarks are predicted in many extensions of the standard model (SM). We explore the possibility that these states could explain not only the long-standing anomaly in the forward–backward asymmetry in b-quark production at LEP, (A_mathrm{FB}^b ), but also the more recent (sim )2(sigma ) deviation of the cross section for the associated Higgs production with top-quark pairs at the LHC, (sigma (pp ightarrow tar{t} H)). Introducing three illustrative models for VLQs with different representations under the SM gauge group, we show that the two anomalies can be resolved while satisfying all other theoretical and experimental constraints. In this case, the three different models predict VLQ states in the 1–2 TeV mass range that can be soon probed at the LHC. In a second step, we discuss the sensitivity on the VLQ masses and couplings that could be obtained by means of a percent level accuracy in the measurement of ratios of partial Higgs decay widths, in particular (Gamma (H ightarrow gamma gamma )/Gamma (H ightarrow ZZ^*)) and (Gamma (H ightarrow bar{b})/Gamma (H ightarrow WW^*)). We show that top and bottom VL partners with masses up to (sim )5?TeV and exotic VLQs with masses in the 10?TeV range can be probed at the high-luminosity LHC.