Matching QCD and HQET at three loops

QCD/HQET matching for the heavy-quark field and heavy-light quark currents with three-loop accuracy is discussed.Comment: Talk at Loops and Legs 2010, Woerlitz, 25-30 April, 7 pages; v2: references adde

Decoupling of heavy quarks in HQET

Decoupling of c-quark loops in b-quark HQET is considered. The decoupling coefficients for the HQET heavy-quark field and the heavy-light quark current are calculated with the three-loop accuracy. The last result can be used to improve the accuracy of extracting f_B from HQET lattice simulations (without c-quark loops). The decoupling coefficient for the flavour-nonsinglet QCD current with n antisymmetrized gamma-matrices is also obtained at three loops; the result for the tensor current (n=2) is new.Comment: JHEP3 documentclass; the results in a computer-readable form can be found at http://www-ttp.physik.uni-karlsruhe.de/Progdata/ttp06/ttp06-25/ V2: a few typos corrected, a few minor text improvements, a few references added; V3: several typos in formulas fixe

Calculating three-loop diagrams in Heavy Quark Effective Theory with integration-by-parts recurrence relations

An algorithm for calculation of three-loop propagator diagrams in HQET, based on integration-by-parts recurrence relations, is constructed and implemented as a REDUCE package Grinder, and in Axiom.Comment: LaTeX2e (JHEP documentclass), 33 pages, 13 eps figures included. The complete paper is also available via the www at http://www-ttp.physik.uni-karlsruhe.de/Preprints/ V2: bug fixes in formulas, improvements of the algorithm, some restructuring. REDUCE package Grinder is available at http://www-ttp.physik.uni-karlsruhe.de/Progdata/ttp00/ttp00-01