Rare FCNC radiative leptonic B<sub>s,d</sub> → γ l<sup>+</sup>l<sup>−</sup> decays in the SM

Dmitri Melikhov, Anastasiia Kozachuk, Nikolai Nikitin

We report our recent results [1] for long-distance QCD effects in the flavour-changing neutral current radiative leptonic decays B → γ ℓ+, ℓ = {e, µ }. One encounters here two distinct types of long-distance effects: those encoded in the B → γ transition form factors induced by the b → q quark currents, and those related to the charm-loop effects. We calculate the B → γ form factors in a broad range of the momentum transfers making use of the relativistic 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 q2 ≥ 5 GeV2. Second, the shape of AFB in B → γ ℓ+ and in B → V ℓ+ (V the vector meson) 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 sizeable reduction of the theoretical uncertainties in AFB at q2 = 5 − 9 GeV2 where it has the sensitivity to physics beyond the SM.

Particle Physics
External organisation(s)
Österreichische Akademie der Wissenschaften (ÖAW), Lomonosov Moscow State University (MSU), Universität Wien, A.I. Alikhanov Institute of Theoretical and Experimental Physics (ITEP)
Proceedings of Science (PoS)
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Publication date
Peer reviewed
Austrian Fields of Science 2012
103034 Particle physics
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