Volume 314 - The European Physical Society Conference on High Energy Physics (EPS-HEP2017) - Flavour Physics and Fundamental Symmetries (Parallel Session). Conveners: Johannes Abrecht; Damir Becirevic; Philip Urquijo. Scientific Secretary: Martino Margoni
Rare FCNF radiative leptonic decays Bγl+l
D. Melikhov*, A. Kozachuk and N. Nikitin
*: corresponding author
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Pre-published on: October 19, 2017
Published on: March 20, 2018
Abstract
We present our recent results for long-distance QCD effects in the flavour-changing neutral current radiative leptonic decays Bγ+, ={e,μ}. One encounters here two distinct types of long-distance effects: those encoded in the Bγ transition form factors induced by the bq quark currents, and those related to the charm-loop effects.

We calculate the Bγ form factors in a broad range of the momentum transfers making use of the relativisitc dispersion approach based on the constituent quark picture which has proven to provide reliable predictions for many weak-transition form factors.

Concerning the description of the charm-loop contributions, we point out two observations: First, the precise description of the charmonium resonances, in particular, the relative phases between ψ and ψ, has impact on the differential distributions and on the forward-backward asymmetry, AFB, in a broad range of q25 GeV2. Second, the shape of AFB in Bγ+ and in BV+ (V the vector meson) {\it in the q2-region between ψ and ψ} provides an unambiguous probe of the relative phases between ψ and ψ. Fixing the latter will lead to a strong reduction of the theoretical uncertainties in AFB at q2=59 GeV2 where it has the sensitivity to physics beyond the SM.
DOI: https://doi.org/10.22323/1.314.0228
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