The ratio of branching fractions of the radiative $B$ decays $B^0\to K^{*0}\gamma$ and $B^{0}s\to \varphi \gamma$ has been measured using $0.37{\mathrm{fb}}^{-1}$ of $pp$ collisions at a center of mass energy of $\sqrt{s}=7\mathrm{TeV}$, collected by the LHCb experiment. The value obtained is $\frac{\mathcal{B}(B^0\to K^{*0}\gamma )}{\mathcal{B}(B^{0}s\to \varphi \gamma )}=1.12\pm {0.08}_{-0.04-0.08}^{+0.06+0.09}$, where the first uncertainty is statistical, the second systematic, and the third is associated with the ratio of fragmentation fractions $f_s/f_d$. Using the world average for $\mathcal{B}(B^0\to K^{*0}\gamma )=(4.33\pm 0.15)\times {10}^{-5}$, the branching fraction $\mathcal{B}(B^{0}s\to \varphi \gamma )$ is measured to be $(3.9\pm 0.5)\times {10}^{-5}$, which is the most precise measurement to date.

• Received 1 March 2012

DOI:https://doi.org/10.1103/PhysRevD.85.112013

This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.

© 2012 CERN, for the LHCb collaboration