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 \( Zb\overline{b} \) 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.
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Acknowledgments
We would like to thank Pier Monni for collaborating in the early stages of this project. We also thank Ayres Freitas, Christophe Grojean, Ulrich Haisch, Jasper Roosmale Nepveu, Emmanuel Stamou, and Doreen Wackeroth for useful discussions, Olivier Mattelaer for his help fixing an issue related to using the systematics module of MadGraph_aMC@NLO in gridpack runs, and Ulrich Haisch and Christophe Grojean for their helpful comments on the manuscript. Z.Q. would like to thank Zongguo Si and the group at Shandong university for helpful discussion and support during the work. The work of Z.Q. was supported by the Helmholtz-OCPC fellowship program in the beginning, and later by the starting research fund of Hangzhou normal university. The Monte Carlo simulations were made possible thanks to the theoc cluster which is managed by the theory-group computing team at DESY. The work of F.B. was partially supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under grant 491245950 and under Germany’s Excellence Strategy — EXC 2121 “Quantum Universe” – 390833306. This work was performed in part at the Aspen Center for Physics, which is supported by National Science Foundation grant PHY-1607611. This research was supported by the Munich Institute for Astro-, Particle and BioPhysics (MIAPbP) which is funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy – EXC-2094 – 390783311.
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Bishara, F., Qian, Z. Complementary constraints on \( Zb\overline{b} \) couplings at the LHC. J. High Energ. Phys. 2023, 88 (2023). https://doi.org/10.1007/JHEP10(2023)088
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DOI: https://doi.org/10.1007/JHEP10(2023)088