Complementary constraints on $$ Zb\overline{b} $$ couplings at the LHC

Abstract

We propose a new strategy to probe the Z boson couplings to bottom and charm quarks at the LHC. In this work we mainly focus on the case of bottom quarks. Here, the Z boson is produced in association with two b-jets and decays to electrons or muons. In this final state, tagging the charge of the b-jets allows us to measure the charge asymmetry and thus to directly probe the $$ Zb\overline{b} $$ Zb b ¯ couplings. The leptonic final state not only allows us to cleanly reconstruct the Z boson but also to mitigate the otherwise overwhelming backgrounds. Furthermore, while LEP could only scan a limited range of dilepton invariant masses, there is no such limitation at the LHC. Consequently, this allows us to make full use of the interference between the amplitudes mediated by a Z boson and a photon. Using the full high-luminosity LHC dataset of 3 ab−1 and with the current flavor and charge-tagging capabilities would allow us to reject the wrong-sign right-handed coupling solution by 4σ. Further improving the charge-tagging efficiency would disfavor it by 6σ.