NNLO QCD Corrections to the B̄ → X s γ Matrix Elements Using Interpolation in m c

نویسنده

  • Matthias Steinhauser
چکیده

One of the most troublesome contributions to the NNLO QCD corrections to B̄ → Xsγ originates from three-loop matrix elements of four-quark operators. A part of this contribution that is proportional to the QCD beta-function coefficient β0 was found in 2003 as an expansion in mc/mb. In the present paper, we evaluate the asymptotic behaviour of the complete contribution for mc ≫ mb/2. The asymptotic form of the β0-part matches the small-mc expansion very well at the threshold mc = mb/2. For the remaining part, we perform an interpolation down to the measured value of mc, assuming that the β0-part is a good approximation at mc = 0. Combining our results with other contributions to the NNLO QCD corrections, we find B(B̄ → Xsγ) = (3.15 ± 0.23) × 10 for Eγ > 1.6 GeV in the B̄-meson rest frame. The indicated error has been obtained by adding in quadrature the following uncertainties: non-perturbative (5%), parametric (3%), higher-order perturbative (3%), and the interpolation ambiguity (3%).

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تاریخ انتشار 2008