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T: Fachverband Teilchenphysik

T 13: QCD (Theorie) 3

T 13.7: Talk

Thursday, March 1, 2012, 18:15–18:30, VG 3.103

Three Loop Contributions to the Matrix Elements in the Variable Flavor Number Scheme — Johannes Blümlein¹, •Alexander Hasselhuhn¹, and Carsten Schneider² — ¹DESY — ²RISC, JKU Linz

The variable flavor number scheme may be used to describe parton distributions in the transition region in which one heavy quark gradually becomes a light flavor. We present first three-loop results to the massive operator matrix elements A_gg and A_gq for the contributions due to bubble topologies ∝ T_F² n_f at general values of the Mellin variable N. The calculation has been performed using higher transcendental functions and by applying modern summation technologies encoded in the package Sigma. These massive operator matrix elements describe the universal contributions in the matching of different flavor sectors, which are the logarithmic and constant contributions in the ratio of m_H²/Q², with Q² the virtuality and m_H the respective heavy quark mass. The framework allows to derive heavy quark parton distributions which are of relevance for calculating specific processes at hadron-hadron colliders.