Reevaluating uncertainties in $$ \overline{B} $$ → Xsγ decay

Abstract

The rare inclusive decay B → X s γ is an important probe of physics beyond the standard model. The largest uncertainty on the decay rate and CP asymmetry comes from operators that appear at order 1/m b in the heavy quark expansion. One of the three leading contributions in the heavy quark expansion, Q q 1 − Q 7γ is described by a non-local function whose moments are related to HQET parameters. We use recent progress in our knowledge of these parameters to better constrain their contributions to the total rate and CP asymmetry.

Towards $$ \overline{B}\to {X}_s\gamma $$ at the NNLO in QCD without interpolation in mc

“…The corresponding 9 range [−1.4, +2.0]% in section 3.5 of ref. [28] is somewhat wider due to a different method of combining uncertainties and using the PDG [59,60] central value of −0.6% for ∆ 0− . When determining our SM predictions below, we calculate B sγ without including the photon emission from the valence/sea quarks and, in the final step, we multiply by 1 + δΓc Γ , employing the number from the r.h.s.…”

“…The final numerical value above has been derived by us from ranges for Λ 17 given in ref. [28], assuming that these ranges can be interpreted as 1σ ones. The remaining parameters on…”

“…which κ V depends were set to the values corresponding to the widest range for Λ 17 in ref. [28]. Since the expression for δN V (3.8) is calculated at the leading order in QCD only, the renormalization scheme for m 2 c in the denominator is unspecified.…”

“…Since they account for all the non-perturbative effects estimated in refs. [28,56], we shall no longer include the overall ±5% non-perturbative uncertainty that entered the analysis of ref. [13] as an input from ref.…”

Long distance effects in inclusive rare B decays and phenomenology of $$ \overline{B} $$→ Xdℓ+ℓ−

“…[43]) and thus represented the main uncertainty in the inclusive b → d + − observables. Further insight into the moments of g 17 was recently given in [99].…”