# Search for the rare decays $B^{0}\to J/\psi \gamma$ and $B^{0}_{s} \to J/\psi \gamma$

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## Abstract

A search for the rare decay of a $B^{0}$ or $B^{0}_{s}$ meson into the final state $J/\psi\gamma$ is performed, using data collected by the LHCb experiment in $pp$ collisions at $\sqrt{s}=7$ and $8$ TeV, corresponding to an integrated luminosity of 3 fb$^{-1}$. The observed number of signal candidates is consistent with a background-only hypothesis. Branching fraction values larger than $1.7\times 10^{-6}$ for the $B^{0}\to J/\psi\gamma$ decay mode are excluded at 90% confidence level. For the $B^{0}_{s}\to J/\psi\gamma$ decay mode, branching fraction values larger than $7.4\times 10^{-6}$ are excluded at 90% confidence level, this is the first branching fraction limit for this decay.

## Figures and captions

 Feynman diagram of the leading contribution to the decay $B _{(s)}\rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \gamma$ in the Standard Model. Radiation of the photon from the other quarks is suppressed by a factor of $\Lambda_{\rm{QCD}}/m_{b}$ [1]. Bs2Jps[..].pdf [9 KiB] HiDef png [164 KiB] Thumbnail [97 KiB] *.C file Mass distribution of signal candidates with the fit result overlaid, allowing for a $B ^0_ s \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \gamma$ signal. data_fit.pdf [34 KiB] HiDef png [470 KiB] Thumbnail [341 KiB] *.C file Observed $\mathrm{CL}_{\mathrm{S}}$ (black points), expected $\mathrm{CL}_{\mathrm{S}}$ (continuous line) and expected 1 and 2 $\sigma$ uncertainty (shaded bands) value as a function of the hypothesized branching fraction for the $B ^0_ s \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \gamma$ decay (left) and $B ^0 \rightarrow { J \mskip -3mu/\mskip -2mu\psi \mskip 2mu} \gamma$ decay (right). The dashed line represents the branching fraction excluded at 90% C.L.. cls.pdf [15 KiB] HiDef png [249 KiB] Thumbnail [173 KiB] *.C file cls_bd.pdf [15 KiB] HiDef png [273 KiB] Thumbnail [189 KiB] *.C file Animated gif made out of all figures. PAPER-2015-044.gif Thumbnail

## Tables and captions

 Summary of systematic uncertainties. Each source is listed with the corresponding uncertainty on the branching fraction for the signal. Table_1.pdf [45 KiB] HiDef png [56 KiB] Thumbnail [27 KiB] tex code

## Supplementary Material [file]

 Supplementary material full pdf supple[..].pdf [209 KiB] Fig1-S.pdf [17 KiB] HiDef png [285 KiB] Thumbnail [204 KiB] *C file Fig2-S.pdf [49 KiB] HiDef png [476 KiB] Thumbnail [347 KiB] *C file Fig3a-S.pdf [34 KiB] HiDef png [476 KiB] Thumbnail [348 KiB] *C file Fig3b-S.pdf [33 KiB] HiDef png [486 KiB] Thumbnail [354 KiB] *C file

Created on 17 August 2019.Citation count from INSPIRE on 20 August 2019.