81 research outputs found
Two-Loop Bosonic Electroweak Corrections to the Muon Lifetime and M_Z-M_W Interdependence
The two-loop electroweak bosonic correction to the muon lifetime and the
M_W-M_Z interdependece is computed using analytical methods of asymptotic
expansion. Combined with previous calculations this copmletes the full two-loop
correction to in the Standard Model. The shift to the prediction of
W-boson mass due to two-loop bosonic corrections does not exceed 1 MeV for the
range of the Higgs mass from 100 to 1000 GeV.Comment: 8 pp, 3 figs, LaTeX, replaced with journal versio
Single-scale diagrams and multiple binomial sums
The -expansion of several two-loop self-energy diagrams with
different thresholds and one mass are calculated. On-shell results are reduced
to multiple binomial sums which values are presented in analytical form.Comment: 10 pp LaTeX, misprints in app. A and minor misprints in the text
correcte
The Differential equation method: calculation of vertex-type diagrams with one non-zero mass
The differential equation method is applied to evaluate analytically two-loop
vertex Feynman diagrams. Three on-shell infrared divergent planar two-loop
diagrams with zero thresholds contributing to the processes Z --> bb bar (for
zero b mass) and/or H --> gg are calculated in order to demonstrate a new
application of this method.Comment: 12 pages, LATEX, uses axodray.st
Two-loop O(as^2) MSSM corrections to the pole masses of heavy quarks
We present the results for two-loop MSSM corrections to the relation between
pole and running masses of heavy quarks up to the order O(as^2). The running
masses are defined in the DR scheme, usually used in multiloop calculations in
supersymmetric theories. The analysis of the value of these corrections in
different regions of the parameter space is provided.Comment: 25 pages, 10 figures, LaTeX2e file; minor changes, files mb.res,
mt.res replaced by new one
The transition form factor
We study the transition form factor,
with the local-duality (LD) version of
QCD sum rules. We analyse the extraction of this quantity from two different
correlators, and $,$ with $P,$ $A,$ and $V$ being the
pseudoscalar, axial-vector, and vector currents, respectively. The QCD
factorization theorem for $F_{\eta_c\gamma\gamma}(Q_1^2,Q_2^2)$ allows us to
fix the effective continuum thresholds for the and correlators
at large values of and some fixed value of . We give arguments that, in the region --, the
effective threshold should be close to its asymptotic value such that the LD
sum rule provides reliable predictions for
We show that, for the experimentally
relevant kinematics of one real and one virtual photon, the result of the LD
sum rule for may be
well approximated by the simple monopole formula
where is the
decay constant, is the -quark charge, and the parameter
lies in the mass range of the lowest vector states.Comment: 9 page
Three-loop massive tadpoles and polylogarithms through weight six
We evaluate the three-loop massive vacuum bubble diagrams in terms of
polylogarithms up to weight six. We also construct the basis of irrational
constants being harmonic polylgarithms of arguments .Comment: 26 pages, 4 ancillary files, v3: version published in JHEP: minor
additions, file with results for massive three-loop form-factor integrals
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