北京工业大学高能组

Complete analysis on QED corrections to Bq → τ +τ −

by Prof. 周 四红

Asia/Shanghai
318 (数理楼)

318

数理楼

Description

Motivated by a dynamical enhancement of the electromagnetic corrections by a power of ΛQCD/mb in Bd,s → μ+ μ− at next-to-leading order (NLO), we extend the QED factorization effects on the leptonic B meson decays with light muon leptons to tauonic final states, Bd,s → τ + τ −, using soft-collinear effective theory (SCET). This extension is necessary owing to the appearance of the large τ mass, which will lead to different power counting in SCET and also different results. We provide a complete NLO electromagnetic corrections to Bd,s → τ + τ −, which include hard functions and hard-collinear functions below the bottom quark mass scale μb. The power enhanced electromagnetic effects from hard-collinear contributions on Bd,s → μ+ μ− discussed before also exist in Bd,s → τ + τ −. However the logarithm term arising from contributions of hard-collinear photon and lepton virtualities for Bd,s → τ+τ− is not large as it is in muon case due to the hard-collinear scale of τ mass, which lead to only approximately 0.04% QED corrections to the branching fraction of Bd,s → τ + τ − compared with overall reduction about 0.5% in Bd,s →μ+μ−.