Abstract
We calculate the differential branching fraction, lepton forward-backward asymmetry and direct CP asymmetry for Bd,s → gamma mathrm{ell}overline{mathrm{ell}} decays with an energetic photon. We employ factorization methods, which result in rigorous next-to-leading order predic- tions in the strong coupling at leading power in the large-energy/heavy-quark expansion, together with estimates of power corrections and a resonance parameterization of sub- leading power form factors in the region of small lepton invariant mass q2. The Bd,s → gamma mathrm{ell}overline{mathrm{ell}} decay shares features of the charged-current decay Bu → gamma mathrm{ell}{overline{nu}}_{mathrm{ell}} ., and the FCNC decays B → {K}^{left(ast right)}mathrm{ell}overline{mathrm{ell}} . As in the former, the leading-power decay rates can be expressed in terms of the B-meson light-cone distribution amplitude and short-distance factors. However, similar to B → {K}^{left(ast right)}mathrm{ell}overline{mathrm{ell}} , four-quark and dipole operators contribute to the Bd,s → gamma mathrm{ell}overline{mathrm{ell}} decay in an essential way, limiting the calculation to q2 ≲ 6 GeV2 below the charmonium resonances in the lepton invariant mass spectrum. A detailed analysis of the main observables and theoretical uncertainties is presented.
Highlights
The hadronic nonperturbative effects entering the theoretical treatment are complex ranging from form factors to resonant contributions, preventing currently theoretical calculations with percent accuracy
In this paper we provided the first analysis of the rare radiative Bq → γdecays in the kinematic regime of large photon energy with QCD factorization techniques, which construct a systematic expansion in inverse powers of large photon energy and heavy quark mass
We investigate the nonlocal corrections to A- and B-type emission from subleading-power form factors
Summary
Since q2/m2Bq = 1 − 2Eγ/mBq = 1 − y, we consider two scalings for q2: 1) anti-hard-collinear (hc) q2 ∼ EγΛQCD or mbΛQCD, in which case the momentum qμ is dominated by its component proportional to the light-like vector nμ+, and. 2) hard (h) q2 ∼ m2b , in which case the photon energy is large, but y is not parametrically close to 1 in the heavy-quark limit. We will be interested in the region with the restriction to q2 6 GeV2, as originally introduced for B → K(∗) ̄ [25], to avoid the charmonium resonance region This upper limit lies somewhat in between these two scalings. Our result will be accurate to these orders for both possible scalings of q2
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
