Tree-level contributions to B ¯ → X s γ

Self Cite

Ongoing efforts to reduce the perturbative uncertainty in theB → X s γ decay rate have resulted in a theory estimate to NNLO in QCD. However, a few contributions from multi-parton final states which are formally NLO are still unknown. These are parametrically small and included in the estimated error from higher order corrections, but must be computed if one is to claim complete knowledge of theB → X s γ rate to NLO. A major part of these unknown pieces are four-body contributions corresponding to the partonic process b → sqqγ. We compute these NLO four-body contributions toB → X s γ, and confirm the corresponding tree-level leading-order results. While the NLO contributions arise from tree-level and one-loop Feynman diagrams, the four-body phase-space integrations make the computation non-trivial. The decay rate contains collinear logarithms arising from the mass regularization of collinear divergences. We perform an exhaustive numerical analysis, and find that these contributions are positive and amount to no more than ∼ 1% of the total rate in the Standard Model, thus confirming previous estimates of the perturbative uncertainty.

“…As a bonus, this step allows one to check the LO result for G (0) ij of ref. [50]. This step is described in section 2.5.…”

Section: Jhep01(2015)115 2 Details Of the Calculationmentioning

confidence: 99%

Section: Renormalizationmentioning

confidence: 99%

“…[50]. At NLO the corresponding counterterm contributions must be included, which cancel the UV divergences from the loop diagrams.…”

Section: Renormalizationmentioning

confidence: 99%

Section: Jhep01(2015)115 2 Details Of the Calculationmentioning

confidence: 99%

Section: Jhep01(2015)115mentioning

confidence: 99%

See 3 more Smart Citations

Four-body contributions to B ¯ → X s γ $$ \overline{B}\to {X}_s\gamma $$ at NLO

Huber

Poradziński

Virto

2015

Self Cite

The (Q7, Q1,2) contribution to B ¯ → X s γ $$ \overline{B}\to {X}_s\gamma $$ at O α s 2 $$ \mathcal{O}\left({\alpha}_{\mathrm{s}}^2\right) $$

Czakon

Fiedler

Huber

et al. 2015

Self Cite

Interference between the photonic dipole operator Q 7 and the current-current operators Q 1,2 gives one of the most important QCD corrections to theB → X s γ decay rate. So far, the O α 2 s part of this correction has been known in the heavy charm quark limit only (m c ≫ m b /2). Here, we evaluate this part at m c = 0, and use both limits in an updated phenomenological study. Our prediction for the CP-and isospin-averaged branching ratio in the Standard Model reads B SM sγ = (3.36±0.23)×10 −4 for E γ > 1.6 GeV.

Model-independent bounds on new physics effects in non-leptonic tree-level decays of B-mesons

Lenz

Tetlalmatzi-Xolocotzi

2020

We present a considerably improved analysis of model-independent bounds on new physics effects in non-leptonic tree-level decays of B-mesons. Our main finding is that contributions of about ±0.1 to the Wilson coefficient of the colour-singlet operator Q 2 of the effective weak Hamiltonian and contributions in the range of ±0.5 (both for real and imaginary part) to Q 1 can currently not be excluded at the 90% C.L.. Effects of such a size can modify the direct experimental extraction of the CKM angle γ by up to 10 • and they could lead to an enhancement of the decay rate difference ∆Γ d of up to a factor of 5 over its SM value-a size that could explain the D0 dimuon asymmetry. Future more precise measurements of the semi-leptonic asymmetries a q sl and the lifetime ratio τ (B s)/τ (B d) will allow to shrink the bounds on tree-level new physics effects considerably. Due to significant improvements in the precision of the non-perturbative input we update all SM predictions for the mixing obervables in the course of this analysis, obtaining: ∆M s = (18.77 ± 0.86) ps −1 , ∆M d = (0.543 ± 0.029) ps −1 , ∆Γ s = (9.1 ± 1.3) • 10 −2 ps −1 , ∆Γ d = (2.6 ± 0.4) • 10 −3 ps −1 , a s sl = (2.06 ± 0.18) • 10 −5 and a d sl = (−4.73 ± 0.42) • 10 −4 .