Quark mass effects in fermionic decays of the Higgs boson in O(α2s) perturbative QCD

Abstract The results of analytical evaluation of O ( α 2 s ) QCD contributions due to the nonvanishing quark masses to Г H→qƒ q ƒ are presented. The “triangle anomaly” type contributions are included. As a byproduct the O ( α 3 s ) logarithmic contributions are evaluated. The results are presented both in terms of running and pole quark masses. The partial decay modes H→b b and H→c c are considered. The calculated corrections decrease the absolute value of large and negative O ( α s 2 ) massless limit coefficient by ≤ 1% in the intermediate mass region and by 1%–20% in the low mass region which, however, is experimentally ruled out. The results are relevant for H→t t decay mode for the higher Higgs mass region where the mass effects are large and important. The high order corrections remove a very large discrepancy between the results for Г H →qƒ q ƒ in terms of running and pole quark masses almost completely and reduce the scale dependence from about 40% to nearly 5%. The remaining theoretical uncertainties are discussed.