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-quark loops in light-light and heavy-light quark currents

Matching of light-light quark currents in QCD with a heavy flavour and in the low-energy effective QCD is calculated in MSbar at two loops. Heavy-light HQET currents are similarly considered.Comment: LaTeX2e, 4 pages, 1 inline figure, requires axodraw.st

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

Massless two-loop self-energy diagram: Historical review

This class of diagrams has numerous applications. Many interesting results have been obtained for it.Comment: Extended version of the talk at the conference Advances of quantum field theory, Dubna, October 2011; 19 pages. V2: 2 references added. V3: 2 references adde