Matching QCD and HQET at three loops
نویسنده
چکیده
QCD problems with a single heavy quarkQ can be treated in a simpler effective theory — HQET, if there exists a 4-velocity v such that the heavyquark momentum is p = mv+k (m is the on-shell mass) and the characteristic residual momentum is small: k ≪ m. QCD operators can be written as series in 1/m via HQET operators; the coefficients in these series are determined by matching on-shell matrix elements in both theories. At the tree level, the heavy-quark field Q is related to the corresponding HQET field Qv (satisfying / vQv = Qv) by [3,4]
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