Search for the decays $B_{(s)}^0\to J\mathrm{/}\psi \gamma$ at LHCb

A search for the rare decays $B_{(s)}^0\to J\mathrm{/}\psi \gamma$ is performed with proton-proton collision data collected by the LHCb experiment, corresponding to integrated luminosities of $3{\mathrm{f}\mathrm{b}}^{-1}$ at centre-of-mass energies of 7 and 8 TeV, and $6{\mathrm{f}\mathrm{b}}^{-1}$ at 13 TeV. Assuming no contribution from $B^0\to J\mathrm{/}\psi \gamma$ decay, an upper limit is set on the branching fraction $\mathcal{B}(B_s^0\to J\mathrm{/}\psi \gamma )<2.9\times {10}^{-6}$ at the 90% confidence level. If instead no contribution from $B_s^0\to J\mathrm{/}\psi \gamma$ decay is assumed, the limit is $\mathcal{B}(B^0\to J\mathrm{/}\psi \gamma )<2.5\times {10}^{-6}$ at the 90% confidence level. These results supersede the previous LHCb results, with the limit for $B_s^0\to J\mathrm{/}\psi \gamma$ improved by a factor of 2.5.