منابع مشابه
QCD corrections to b → c transitions at zero recoil
Complete two-loop QCD corrections to b → c transitions are presented in the limit of zero recoil. Vector and axial-vector coefficients ηA,V are calculated analytically in the limit of equal beauty and charm masses, and a series appoximation is obtained for the general mass case. ηA is crucial for the determination of the absolute value of the Cabibbo-Kobayashi-Maskawa matrix element Vcb. The tw...
متن کاملPerturbative corrections to zero recoil inclusive B decay sum rules
Comparing the result of inserting a complete set of physical states in a time ordered product of b decay currents with the operator product expansion gives a class of zero recoil sum rules. They sum over physical states with excitation energies less than ∆, where ∆ is much greater than the QCD scale and much less than the heavy charm and bottom quark masses. These sum rules have been used to de...
متن کاملHigher-Order Perturbative Corrections to b → c Transitions at Zero Recoil
We estimate the two-loop perturbative corrections to zero-recoil matrix elements of the flavour-changing currents c̄ γμb and c̄ γγ5 b by calculating the terms of order nf α 2 s and substituting the dependence on the number of flavours by the first coefficient of the β-function. Both for vector and axial vector currents, we find moderate twoloop corrections below 1% in magnitude. Using the Brodsky...
متن کاملTwo-loop QCD corrections to b-->c transitions at zero recoil.
Complete two-loop QCD corrections to b ! c transitions are presented in the limit of zero recoil. Vector and axial-vector coeecients A;V are calculated analytically in the limit of equal beauty and charm masses, and a series appoximation is obtained for the general mass case. A is crucial for the determination of the absolute value of the Cabibbo-Kobayashi-Maskawa matrix element V cb. The two-l...
متن کاملTwo - loop QCD Corrections to b → c Transitions at Zero Recoil : Analytical Results
We present analytical results for the O(α s) contributions to the functions ηA and ηV which parameterize QCD corrections to semileptonic b → c transitions at zero recoil. Previously obtained approximate results are confirmed. The methods of computing the relevant twoloop diagrams with two mass scales are discussed in some detail.
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ژورنال
عنوان ژورنال: EPJ Web of Conferences
سال: 2018
ISSN: 2100-014X
DOI: 10.1051/epjconf/201817513003