Search for the B0s → μ + μ − γ decay

A search for the fully reconstructed → μ+μ−γ decay is performed at the LHCb experiment using proton-proton collisions at = 13 TeV corresponding to an integrated luminosity of 5.4 fb−1. No significant signal is found and upper limits on the branching fraction in intervals of the dimuon mass are set= 13 TeV corresponding to an integrated luminosity of 5.4 fb−1. No significant signal is found and upper limits on the branching fraction in intervals of the dimuon mass are set B(B0s → µ+µ−γ) < 4.2 × 10−8, m(µ+µ−) ∈ [2mµ, 1.70] GeV/c2 B(B0s → µ+µ−γ) < 7.7 × 10−8, m(µ+µ−) ∈ [1.70, 2.88] GeV/c2 B(B0s → µ+µ−γ) < 4.2 × 10−8, m(µ+µ−) ∈ [3.92, mB0s] GeV/c2 at 95% confidence level. Additionally, upper limits are set on the branching fraction in the [2mμ, 1.70] GeV/c2 dimuon mass region excluding the contribution from the intermediate ϕ(1020) meson, and in the region combining all dimuon-mass intervals.