1,319 research outputs found
The Algebraic Method
Combining the effect of an intermediate renormalization prescription (zero
momentum subtraction) and the background field method (BFM), we show that the
algebraic renormalization procedure needed for the computation of radiative
corrections within non-invariant regularization schemes is drastically
simplified. The present technique is suitable for gauge models and, here, is
applied to the Standard Model. The use of the BFM allows a powerful
organization of the counterterms and avoids complicated Slavnov-Taylor
identities. Furthermore, the Becchi-Rouet-Stora-Tyutin (BRST) variation of
background fields plays a special role in disentangling Ward-Takahashi
identities (WTI) and Slavnov-Taylor identities (STI). Finally, the strategy to
be applied to physical processes is exemplified for the process .Comment: Latex, 38 page
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 relation between the and on-shell quark mass
In this contribution we discuss the four-loop relation between the on-shell
and definition of heavy quark masses which is applied to the
top, bottom and charm case. We also present relations between the quark mass and various threshold mass definitions and discuss the
uncertainty at next-to-next-to-next-to-leading order.Comment: 9 pages, 2 figures, to appear in the proceedings of the 12th
International Symposium on Radiative Corrections (Radcor 2015) and LoopFest
XIV (Radiative Corrections for the LHC and Future Colliders
A planar four-loop form factor and cusp anomalous dimension in QCD
We compute the fermionic contribution to the photon-quark form factor to
four-loop order in QCD in the planar limit in analytic form. From the divergent
part of the latter the cusp and collinear anomalous dimensions are extracted.
Results are also presented for the finite contribution. We briefly describe our
method to compute all planar master integrals at four-loop order.Comment: 19 pages, 3 figures, v2: typo in (2.3) fixed and coefficients in
(2.6) corrected; references added and correcte
Quark mass relations to four-loop order
We present results for the relation between a heavy quark mass defined in the
on-shell and scheme to four-loop order. The method to compute
the four-loop on-shell integral is briefly described and the new results are
used to establish relations between various short-distance masses and the
quark mass to next-to-next-to-next-to-leading order accuracy.
These relations play an important role in the accurate determination of the
heavy quark masses.Comment: 6 pages, v2: references added, typos in eq.(16) fixed, matches
published versio
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
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