Order alpha_s^2 beta_0 Correction to the Charged Lepton Spectrum in b \to c \ell \barν_\ell decays

Abstract

We compute the α_s^2β_0 part of the two-loop QCD corrections to the charged lepton spectrum in b \to c \ell \barν_\ell decays and find them to be about 50\% of the first order corrections at all lepton energies, except those close to the end point. Including these corrections we extract the central values \barΛ=0.33 GeV and λ_1=-0.17 GeV^2 for the HQET matrix elements and use them to determine the $\overline{\rm MS}$ b and c quark masses, and |V_{cb}|.