Perturbative corrections to the determination of Vub from the P+ spectrum in B->X_u l nu

Abstract

We investigate the relation between the E_gamma spectrum in B->X_s gamma decay and the P+ spectrum in semileptonic B->X_u l nu decay (P+ is the hadronic energy minus the absolute value of the hadronic three-momentum), which provides in principle the theoretically simplest determination of Vub from any of the "shape function regions" of B->X_u l nu spectra. We calculate analytically the P+ spectrum to order alpha_s^2 beta_0, and study its relation to the B->X_s gamma photon spectrum to eliminate the leading dependence on nonperturbative effects. We compare the result of fixed order perturbation theory to the next-to-leading log renormalization group improved calculation, and argue that fixed order perturbation theory is likely to be a more appropriate expansion. Implications for the perturbative uncertainties in the determination of Vub from the P+ spectrum are discussed.

reference added, to appear in PRD

References in corpus (2)

• Renormalization-Group Improved Calculation of the B->Xs+gamma Branching Ratio
• Subleading Shape Functions in Inclusive B Decays

Cited by in corpus (13)

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• Running-coupling effects in the triple-differential charmless semileptonic decay width
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• A New Method for Calculating Differential Distributions Directly in Mellin Space
• High order perturbative corrections to the determination of |Vub| from the P+ spectrum in B -> Xu l nu
• Non-Universal Effects in Semi-Inclusive B Decays