Probing the $H\gamma \gamma$ coupling via Higgs exclusive decay into quarkonia plus a photon at the HL-LHC

Abstract

It is well know that the precise measurement of $H\to \gamma \gamma$ can generate two degenerate parameter spaces of $H\gamma \gamma$ anomalous coupling. We propose to utilize the exclusive Higgs rare decays $H\to {\rm Y}(ns)+\gamma$ to break above mentioned degeneracy and further to constrain the $H\gamma \gamma$ anomalous coupling at the HL-LHC. We demonstrate that the branching ratios of $H\to {\rm Y}(ns)+\gamma$ can be significantly enhanced in the non-SM-like parameter space from $H\to \gamma \gamma$ measurement, due to the destructive interference between the direct and indirect production of ${\rm Y}(ns)$ in the SM. By applying the NRQCD factorization formalism, we calculate the partial decay widths of $H\to {\rm Y}(ns)+\gamma$ at the NLO accuracy of ${\alpha }_s$. We show that it is hopeful to break such degenerate parameter space at the HL-LHC if we can further highly suppress the background and enhance the signal efficiency compared to the ATLAS preliminary simulation.

Comments: 6 pages, 3 figures, published version