Journal Article

Towards B¯→Xsγ at the NNLO in QCD without interpolation in mc

Rehman, Abdur, Steinhauser, Matthias, Misiak, Miko-laj

2020

Overview

A bstract Strengthening constraints on new physics from the B ¯ → X s γ branching ratio requires improving accuracy in the measurements and the Standard Model predictions. To match the expected Belle-II accuracy, Next-to-Next-to-Leading Order (NNLO) QCD corrections must be calculated without the so-far employed interpolation in the charm- quark mass m c . In the process of evaluating such corrections at the physical value of mc , we have finalized the part coming from diagrams with closed fermion loops on the gluon lines that contribute to the interference of the current-current and photonic dipole operators. We confirm several published results for corrections of this type, and supplement them with a previously uncalculated piece. Taking into account the recently improved estimates of non-perturbative contributions, we find ℬ sγ = (3 . 40 ± 0 . 17) × 10 − 4 and R γ ≡ ℬ s + d γ / ℬ c ℓ v ¯ = (3 . 35 ± 0 . 16) × 10 − 3 for E γ > 1 . 6 GeV in the decaying meson rest frame.

• Publisher: Springer Berlin Heidelberg,Springer Nature B.V
• Subject: Accuracy / Charm (particle physics) / Classical and Quantum Gravitation / Dipoles / Elementary Particles / Fermions / Gluons / High energy physics / Interpolation / Physics / Physics and Astronomy / Quantum chromodynamics / Quantum Field Theories / Quantum Field Theory / Quantum Physics / Quarks / Regular Article - Theoretical Physics / Relativity Theory / Standard model (particle physics) / String Theory