965 research outputs found
On the Generalized Harmonic Polylogarithms of One Complex Variable
We describe how to compute numerically in the complex plain a set of
Generalized Harmonic Polylogarithms (GHPLs) with square roots in the weights,
using the C++/GiNaC numerical routines of Vollinga and Weinzierl. As an
example, we provide the numerical values of the NLO electroweak light-fermion
corrections to the Higgs boson production in gluon fusion in the case of
complex W and Z masses.Comment: 25 pages, 1 figur
Differential equations and massive two-loop Bhabha scattering: the B5l2m3 case
The two-loop box contributions to massive Bhabha scattering may be reduced to
two-loop box master integrals (MIs) with five, six, and seven internal lines,
plus vertices and self energies. The self-energy and vertex MIs may be solved
analytically by the differential equations (DE) method. This is true for only
few of the box masters. Here we describe some details of the analytical
determination, including constant terms in ep=(4-d)/2, of the complicated
topology B5l2m3 (with 5 lines, 2 of them being massive). With the DE approach,
three of the four coupled masters have been solved in terms of (generalized)
standard Harmonic Polylogarithms.Comment: 5 pages, 2 figures, contribution to RADCOR 2005, Oct 2-7, 2005,
Shonan Village, Japan, to appear in Nucl. B (Proc. Suppl.
Top Quark Production at Hadron Colliders: an Overview
The study of the properties of the top quark is one of the main goals of the
Large Hadron Collider (LHC) physics program. The experimental precision
expected at the LHC requires the calculation of several top-quark related
observables beyond leading order in the strong coupling constant. In this work
we briefly review the status of the theoretical predictions for the top-quark
production processes at hadron colliders. Special attention is devoted to
recent progress in the calculation of next-to-next-to-leading-order corrections
to the top-quark pair production cross section.Comment: Submitted to the proceedings of "The 2009 Europhysics Conference on
High Energy Physics", July 16 - 22, 2009, Krakow, Poland. References adde
Matching perturbative and Parton Shower corrections to Bhabha process at flavour factories
We report on a high-precision calculation of the Bhabha process in Quantum
Electrodynamics, of interest for precise luminosity determination of
electron-positron colliders involved in R measurements in the region of
hadronic resonances. The calculation is based on the matching of exact
next-to-leading order corrections with a Parton Shower algorithm. The accuracy
of the approach is demonstrated in comparison with existing independent
calculations and through a detailed analysis of the main components of
theoretical uncertainty, including two-loop corrections, hadronic vacuum
polarization and light pair contributions. The calculation is implemented in an
improved version of the event generator BABAYAGA with a theoretical accuracy of
the order of 0.1%. The generator is now available for high-precision
simulations of the Bhabha process at flavour factories.Comment: 34 pages, 8 figures, uses elsart.cls. Version to appear on Nuclear
Physics
Two-Loop QED Heavy-Flavor Contribution to Bhabha Scattering
We briefly review the status of the calculation of next-to-next-to-leading
order corrections to large angle Bhabha scattering in pure QED. In particular,
we focus on the analytic calculation of the two-loop virtual corrections
involving a heavy-flavor fermion loop, which was recently completed. We
conclude by assessing the numerical impact of these corrections on the Bhabha
scattering cross section at colliders operating at a center of mass energy of 1
GeV and at the future ILC.Comment: 6 pages, 2 figures. Contribution to the Proceedings of the 9th DESY
workshop on "Loops and Legs in Quantum Field Theory", Sondershausen, April
2008. References adde
Two-Loop Master Integrals for the Planar QCD Massive Corrections to Di-photon and Di-jet Hadro-production
We present the analytic calculation of the Master Integrals necessary to
compute the planar massive QCD corrections to Di-photon (and Di-jet) production
at hadron colliders. The masters are evaluated by means of the differential
equations method and expressed in terms of multiple polylogarithms and one- or
two-fold integrals of polylogarithms and irrational functions, up to
transcendentality four.Comment: 20 pages, ancillary file
Two-Loop QCD Corrections to the Heavy Quark Form Factors: Axial Vector Contributions
We consider the Z Q Qbar vertex to second order in the QCD coupling for an
on-shell massive quark-antiquark pair and for arbitrary momentum transfer of
the Z boson. We present closed analytic expressions for the two
parity-violating form factors of that vertex at the two-loop level in QCD,
excluding the contributions from triangle diagrams. These form factors are
expressed in terms of 1-dimensional harmonic polylogarithms of maximum weight
4.Comment: 57 pages, 5 figures. All the results in Section 6 of the paper are
available in an electronic form in the file formulas.in
Differential equations and high-energy expansion of two--loop diagrams in D dimensions
New method of calculation of master integrals using differential equations
and asymptotical expansion is presented. This method leads to the results exact
in space-time dimension having the form of the convergent power series. As
an application of this method, we calculate the two--loop master integral for
"crossed--triangle" topology which was previously known only up to O(\ep)
order. The case when a topology contains several master integrals is also
considered. We present an algorithm of the term-by-term calculation of the
asymptotical expansion in this case and analyze in detail the "crossed--box"
topology with three master integrals.Comment: 13 pages,8 figures, uses elsart.cls. Misprints correcte
Two-loop QED Corrections to Bhabha Scattering
Recent developments in the calculation of the NNLO corrections to the Bhabha
scattering differential cross section in pure QED are briefly reviewed and
discussed.Comment: 5 pages, 4 figures, to appear in the proceedings of the 7th
International Symposium on Radiative Corrections (RADCOR05), Shonan Village,
Japan, 200
Two-loop QCD corrections to the vector form factors for the heavy-quark photo-production
We review on the calculation of the heavy-quark photo-production vector form
factors, with the full dependence on the mass of the heavy-quark. The Feynman
diagrams are evaluated within the dimensional regularization scheme and
expressed in Laurent series of , where is the space-time
dimension. The coefficients of the expansion are expressed in terms of harmonic
polylogarithms. The numerical evaluation of the analytical formulas and the
threshold limit of our results are presented.Comment: Talk presented at the 11th International QCD Conference: QCD04,
Montpellier, France, 5-10 July 2004; 4 pages, 4 figure
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