227 research outputs found
The 4-loop quark mass anomalous dimension and the invariant quark mass
We present the analytical calculation of the four-loop quark mass anomalous
dimension in Quantum Chromodynamics within the minimal subtraction scheme. On
the basis of this result we find that the so-called invariant quark mass is a
very good reference mass for the accurate evolution of the running MS-bar quark
mass in phenomenological applications. We also obtain for the first time a
complete 4-th order perturbative QCD expression for a physical quantity, the
total Higgs boson decay rate into hadrons, and analyze the infrared fixed point
for this case.Comment: 11 pages, Late
The renormalization of the axial anomaly in dimensional regularization
The prescription for the -matrix within dimensional regularization
in multiloop calculations is elaborated. The three-loop anomalous dimension of
the singlet axial current is calculated.Comment: 11 pages, 1 figure available on request from the author,
NIKHEF-H/92-1
The next-to-leading QCD approximation to the Ellis-Jaffe sum rule
The \alpha_s^2 correction to the Ellis-Jaffe sum rule for the structure
function g_1 of polarized deep inelastic lepton-nucleon scattering is
calculated.Comment: 9 pages, latex, CERN-TH.7208/9
The Large Quark Mass Expansion of Gamma (Z^0 -> hadrons) and Gamma(tau^- -> nu_tau + hadrons) in the Order alpha_s^3
We present the analytical correction to the decay rate
into hadrons. We calculate this correction up to (and including) terms of the
order in the large top quark mass expansion. We rely on
the technique of the large mass expansion of individual Feynman diagrams and
treat its application in detail. We convert the obtained results of six flavour
QCD to the results in the effective theory with five active flavours, checking
the decoupling relation of the QCD coupling constant. We also derive the large
charm quark mass expansion of the semihadronic lepton decay rate in the
approximation.Comment: Postscript generation repaired, The complete postscript file of this
article, including figures, is now available at
ftp://nikhefh.nikhef.nl/pub/preprints/H94-30.ps.g
The alpha_s^3 correction to Gamma (Z^0 -> hadrons)
We present the alpha_s^3 correction to the Z^0 decay rate into hadrons in the
limit m_top >> m_Z.Comment: 7pages, NIKHEF-H/93-2
Dimensional Reduction applied to QCD at three loops
Dimensional Reduction is applied to \qcd{} in order to compute various
renormalization constants in the \drbar{} scheme at higher orders in
perturbation theory. In particular, the function and the anomalous
dimension of the quark masses are derived to three-loop order. Special emphasis
is put on the proper treatment of the so-called -scalars and the
additional couplings which have to be considered.Comment: 13 pages, minor changes, references adde
The four-loop beta-function in Quantum Chromodynamics
We present the analytical calculation of the four-loop QCD beta-function
within the minimal subtraction scheme.Comment: 9 pages, Latex, 1 figure, uses axodraw.st
The four-loop DRED gauge beta-function and fermion mass anomalous dimension for general gauge groups
We present four-loop results for the gauge beta-function and the fermion mass
anomalous dimension for a gauge theory with a general gauge group and a
multiplet of fermions transforming according to an arbitrary representation,
calculated using the dimensional reduction scheme. In the special case of a
supersymmetric theory we confirm previous calculations of both the gauge
beta-function and the gaugino mass beta-function.Comment: 44 pages, added references (v2) minor changes (v3
The (alpha_s)^3 approximation of Quantum Chromodynamics to the Ellis-Jaffe sum rule
We present the analytical calculation in perturbative Quantum Chromodynamics
of the (alpha_s)^3 contribution to the Ellis-Jaffe sum rule for the structure
function g1 of polarized deep inelastic lepton-nucleon scattering.Comment: 11 pages, Late
Production of a pseudo-scalar Higgs boson at hadron colliders at next-to-next-to leading order
The production cross section for pseudo-scalar Higgs bosons at hadron
colliders is computed at next-to-next-to-leading order (NNLO) in QCD. The
pseudo-scalar Higgs is assumed to couple only to top quarks. The NNLO effects
are evaluated using an effective lagrangian where the top quarks are integrated
out. The NNLO corrections are similar in size to those found for scalar Higgs
boson production.Comment: 20 pages, 6 figures, JHEP style, Minor changes, Journal reference
adde
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