Running couplings for the simultaneous decoupling of heavy quarks
arXiv:hep-ph/0507278 · doi:10.1016/j.physletb.2006.01.064
Abstract
Scale-invariant running couplings are constructed for several quarks being decoupled together, without reference to intermediate thresholds. Large-momentum scales can also be included. The result is a multi-scale generalization of the renormalization group applicable to any order. Inconsistencies in the usual decoupling procedure with a single running coupling can then be avoided, e.g. when cancelling anomalous corrections from t,b quarks to the axial charge of the proton.
12 pages, 1 figure, version to appear in PLB. Pages 8-11 and Fig. 1 are new, with consequent changes to the abstract, page 2, and the references. We show that our multi-scale renormalization group is needed to achieve anomaly cancellation in t,b decoupling from the weak neutral current, and extend it to include large momenta