The presence of thresholds for finite quark masses alters the behavior of the QCD coupling constant. While the alterations are small they can have significant influence on the determination of the scale parameter Λ. Part of the discrepancy between recent high Q2 determinations of Λ and older low Q2 determinations can be attributed to charm and bottom thresholds. We present simple, analytic expressions for the mass dependence of α(Q2) and exploit these to discuss Λ determinations, scale breaking and the phenomenon of temporary freedom when more than 17 quark flavors exist.
ASJC Scopus subject areas
- Physics and Astronomy (miscellaneous)