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

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 $B_s^0$, $B^0$ and $\hat{I}{\cdot }_b$ 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 $\mathcal{B}(B_s^0\to {\hat{I}}^3{\hat{I}}^3)<2.7\times 10^{-5}$, $\mathcal{B}(B^0\to {\hat{I}}^3{\hat{I}}^3)<0.83\times 10^{-5}$, and $\ddot{I}ƒ(pp\to \hat{I}{\cdot }_{b}X)\times \mathcal{B}(\hat{I}{\cdot }_b\to {\hat{I}}^3{\hat{I}}^3)<765\text{pb}$ at 95 % confidence level.

All figures and tables, along with machine-readable versions and any supplementary material and additional information, are available at https://lbfence.cern.ch/alcm/public/analysis/full-details/1619/ (LHCb public pages)