Search for resonances decaying to photon pairs with masses between 4.9 and 19.4 GeV

TL;DR

This paper searches for axion-like particles and meson decays into photon pairs within a specific mass range using LHCb data, setting upper limits on their production and decay rates due to no observed excess.

Contribution

It provides the first search for ALPs decaying to photon pairs in the 4.9 to 19.4 GeV mass range with LHCb data, establishing new upper limits.

Findings

No significant excess observed.

Upper limits set on ALP production cross-section.

Branching fraction limits for meson decays.

Abstract

A search is presented for axion-like particles (ALPs) with masses between 4.9 and 19.4 GeV decaying to a pair of photons, using proton-proton collisions collected with the LHCb detector during 2018 at a centre-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 2.1 fb$^{-1}$. The same strategy and sample is used to search for the decays of the $B^0_s$, $B^0$ and $\eta_b$ mesons into photon pairs. No significant excess is found. Upper limits on the photon-pair branching fraction times the cross-section of ALP production are determined as a function of the ALP mass. Limits on the branching fractions of the beauty states are determined to be $\mathcal{B}(B^0_s\to\gamma\gamma)<2.7\times10^{-5}$, $\mathcal{B}(B^0\to\gamma\gamma)<0.83\times10^{-5}$, and $ \sigma(pp\to\eta_b X)\times\mathcal{B}(\eta_b\to\gamma\gamma)<765\,\text{pb}$ at 95 % confidence level.