574 research outputs found
Ghost contributions to charmonium production in polarized high-energy collisions
In a previous paper [Phys. Rev. D 68, 034017 (2003)], we investigated the
inclusive production of prompt J/psi mesons in polarized hadron-hadron,
photon-hadron, and photon-photon collisions in the factorization formalism of
nonrelativistic quantum chromodynamics providing compact analytic results for
the double longitudinal-spin asymmetry A_{LL}. For convenience, we adopted a
simplified expression for the tensor product of the gluon polarization
four-vector with its charge conjugate, at the expense of allowing for ghost and
anti-ghosts to appear as external particles. While such ghost contributions
cancel in the cross section asymmetry A_{LL} and thus were not listed in our
previous paper, they do contribute to the absolute cross sections. For
completeness and the reader's convenience, they are provided in this addendum.Comment: 5 page
Four-loop quark form factor with quartic fundamental colour factor
We analytically compute the four-loop QCD corrections for the colour
structure to the massless non-singlet quark form factor. The
computation involves non-trivial non-planar integral families which have master
integrals in the top sector. We compute the master integrals by introducing a
second mass scale and solving differential equations with respect to the ratio
of the two scales. We present details of our calculational procedure.
Analytical results for the cusp and collinear anomalous dimensions, and the
finite part of the form factor are presented. We also provide analytic results
for all master integrals expanded up to weight eight.Comment: 16 pages, 2 figure
Three-loop massive form factors: complete light-fermion and large- corrections for vector, axial-vector, scalar and pseudo-scalar currents
We compute the three-loop QCD corrections to the massive quark form factors
with external vector, axial-vector, scalar and pseudo-scalar currents. All
corrections with closed loops of massless fermions are included. The
non-fermionic part is computed in the large- limit, where only planar
Feynman diagrams contribute.Comment: 33 page
Supersymmetric Corrections to the Threshold Production of Top Quark Pairs
In this paper we investigate supersymmetric effects to the threshold
production cross section of top quark pairs in electron positron annihilation.
In particular, we consider the complete one-loop corrections from the strong
and weak sector of the Minimal Supersymmetric Standard Model.Comment: 18 pages, 7 figure
Gauge Coupling Beta Functions in the Standard Model to Three Loops
In this paper we compute the three-loop corrections to the beta functions of
the three gauge couplings in the Standard Model of particle physics using the
minimal subtraction scheme and taking into account Yukawa and Higgs self
couplings.Comment: 4 pages, 1 figure, v2: minor changes, references adde
Four-loop quark form factor with quartic fundamental colour factor
We analytically compute the four-loop QCD corrections for the colour structure (d F abcd )2 to the massless non-singlet quark form factor. The computation involves non-trivial non-planar integral families which have master integrals in the top sector. We compute the master integrals by introducing a second mass scale and solving differential equations with respect to the ratio of the two scales. We present details of our calculational procedure. Analytical results for the cusp and collinear anomalous dimensions, and the finite part of the form factor are presented. We also provide analytic results for all master integrals expanded up to weight eight
Three-loop massive form factors: complete light-fermion and large-N corrections for vector, axial-vector, scalar and pseudo-scalar currents
We compute the three-loop QCD corrections to the massive quark form factors with external vector, axial-vector, scalar and pseudo-scalar currents. All corrections with closed loops of massless fermions are included. The non-fermionic part is computed in the large-N c limit, where only planar Feynman diagrams contribute
Three-loop massive form factors: complete light-fermion corrections for the vector current
We compute the three-loop QCD corrections to the massive
quark-anti-quark-photon form factors and involving a closed loop of
massless fermions. This subset is gauge invariant and contains both planar and
non-planar contributions. We perform the reduction using FIRE and compute the
master integrals with the help of differential equations. Our analytic results
can be expressed in terms of Goncharov polylogarithms. We provide analytic
results for all master integrals which are not present in the large-
calculation considered in Refs. [1,2].Comment: 22 page
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