Searches for exclusive Higgs and Z boson decays into a vector quarkonium state and a photon using 139 fb - 1 of ATLAS √s=13 TeV proton–proton collision data

Barton, A.E. and Bertram, I.A. and Borissov, G. and Bouhova-Thacker, E.V. and Ferrando, J. and Fox, H. and Henderson, R.C.W. and Jones, R.W.L. and Kartvelishvili, V. and Love, P.A. and Meng, L. and Muenstermann, D. and Rybacki, K. and Smizanska, M. and Spinali, S. and Wharton, A.M. and Yexley, Melissa (2023) Searches for exclusive Higgs and Z boson decays into a vector quarkonium state and a photon using 139 fb - 1 of ATLAS √s=13 TeV proton–proton collision data. European Physical Journal C, 83 (9): 781.

Abstract

Searches for the exclusive decays of Higgs and Z bosons into a vector quarkonium state and a photon are performed in the μ+μ-γ final state with a proton–proton collision data sample corresponding to an integrated luminosity of 139 fb - 1 collected at s=13 TeV with the ATLAS detector at the CERN Large Hadron Collider. The observed data are compatible with the expected backgrounds. The 95% confidence-level upper limits on the branching fractions of the Higgs boson decays into J/ψγ , ψ(2S)γ , and Υ(1S,2S,3S)γ are found to be 2.0 × 10 - 4 , 10.5 × 10 - 4 , and (2.5 , 4.2 , 3.4) × 10 - 4 , respectively, assuming Standard Model production of the Higgs boson. The corresponding 95% CL upper limits on the branching fractions of the Z boson decays are 1.2 × 10 - 6 , 2.4 × 10 - 6 , and (1.1 , 1.3 , 2.4) × 10 - 6 . An observed 95% CL interval of (- 133 , 175) is obtained for the κ c/ κ γ ratio of Higgs boson coupling modifiers, and a 95% CL interval of (- 37 , 40) is obtained for κ b/ κ γ .