Update of the Standard-Model prediction for $\bar{B}\to X_s\gamma$

Abstract

We report on two recent calculations on the inclusive radiative decay $\bar{B}\to X_s\gamma$, notably multi-parton contributions at NLO and the $Q_{1,2}-Q_7$ interference at NNLO for the physical value of the charm-quark mass. The former calculation formally completes $\bar{B}\to X_s\gamma$ at NLO in QCD at leading power, the latter removes a long-standing $\pm 3\%$ uncertainty arising from interpolation in $m_c$. The updated Standard-Model prediction for the CP- and isospin-averaged branching ratio reads ${\mathcal{B}}_{s\gamma }^{\mathrm{SM}}=(3.54\pm 0.14)\times 10^{-4}$ for photon energies $E_{\gamma }>1.6\mathrm{GeV}$ in the $B$-meson rest frame. This value is in good agreement with the current experimental average ${\mathcal{B}}_{s\gamma }^{\exp }=(3.49\pm 0.19)\times 10^{-4}$.

Comments: 13 pages, 6 figures, 1 table. Contribution to the proceedings of "Loops and Legs in Quantum Field Theory (LL2026), 12-17, April, 2026, Bayreuth, Germany"