Monday, July 15, 2013

1307.3508 (E. G. de Oliveira et al.)

Treatment of heavy quarks in QCD    [PDF]

E. G. de Oliveira, A. D. Martin, M. G. Ryskin, A. G. Shuvaev
We show that to correctly describe the effects of the heavy-quark mass, m_Q, in DGLAP evolution, it is necessary to work in the so-called `physical' scheme. In this way, we automatically obtain a smooth transition through the heavy-quark thresholds. Moreover, we show that to obtain NLO accuracy, it is sufficient to account for the heavy-quark mass, m_Q, just in the LO (one-loop) splitting function. The use of the MS-bar factorisation scheme is not appropriate, since at NLO we deal with a mixture of quarks and gluon (that is, the mass of the heavy parton is not well-defined). The formulae for the explicit m_Q dependence of the splitting functions, and for alpha_s, are presented.
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