30 research outputs found
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
adde
On the -quark running mass in QCD and the SM
We consider electroweak corrections to the relation between the running
mass of the quark in the five-flavor
QCDQED effective theory and its counterpart in the Standard Model (SM).
As a bridge between the two parameters, we use the pole mass of the
quark, which can be calculated in both models. The running mass is not a
fundamental parameter of the SM Lagrangian, but the product of the running
Yukawa coupling and the Higgs vacuum expectation value. Since there exist
different prescriptions to define the latter, the relations considered in the
paper involve a certain amount of freedom. All the definitions can be related
to each other in perturbation theory. Nevertheless, we argue in favor of a
certain gauge-independent prescription and provide a relation which can be
directly used to deduce the value of the Yukawa coupling of the quark at
the electroweak scale from its effective QCD running mass. This approach allows
one to resum large logarithms systematically. Numerical analysis
shows that, indeed, the corrections to the proposed relation are much smaller
than those between and .Comment: 19 pages, 4 figures, misprints corrected (thanks to S. Martin),
results not affecte
The Boltzmann equation for colourless plasmons in hot QCD plasma. Semiclassical approximation
Within the framework of the semiclassical approximation, we derive the
Boltzmann equation describing the dynamics of colorless plasmons in a hot QCD
plasma. The probability of the plasmon-plasmon scattering at the leading order
in the coupling constant is obtained. This probability is gauge-independent at
least in the class of the covariant and temporal gauges. It is noted that the
structure of the scattering kernel possesses important qualitative difference
from the corresponding one in the Abelian plasma, in spite of the fact that we
focused our study on the colorless soft excitations. It is shown that
four-plasmon decay is suppressed by the power of relative to the process of
nonlinear scattering of plasmons by thermal particles at the soft momentum
scale. It is stated that the former process becomes important in going to the
ultrasoft region of the momentum scale.Comment: 41, LaTeX, minor changes, identical to published versio