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

Progress in multiloop calculations

I briefly summarize the talks on calculation of multiloop Feynman diagrams presented at ACAT'2002 (Moscow University).Comment: Section summary talk at ACAT'2002 (Moscow

Renormalization of HQET at Three Loops

Three-loop propagator diagrams in HQET can be reduced, using integration by parts, to 8 basis integrals: 5 trivial ones, two expressible via 3F2, and one only known up to \epsilon^0. Calculation of the heavy-quark propagator in HQET is considerably simplified by the non-abelian exponentiation theorem.Comment: Talk at the QCD workshop, Martina Franca, 17-20 June, to be published in the Proceedings; LaTeX2e, aipproc document class (included), 7 pages, 7 eps figures (included

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