arXiv subjects

Costas Papadopoulos

Publications and source records attributed to Costas Papadopoulos.

4 recordsLinked to original sources

arXiv2025

Towards numerical two-loop integrand reduction

We present a method for the integrand-level reduction of two-loop helicity amplitudes in both $d=4-2\epsilon$ and $d=4$ dimensions. The amplitude is expressed in terms of a set of Feynman integrals and their coefficients that depend on the external kinematics. The analysis presented in this paper, in conjunction with the ongoing development of the computational framework $\text{HELAC-2LOOP}$, paves the road for the construction of an automated program for two-loop amplitude calculations for arbitrary scattering processes.

hep-ph↗

arXiv2024

Two-Loop Amplitude Reduction with HELAC

We discuss recent progress towards extending the Helac framework to the calculation of two-loop amplitudes. A general algorithm for the automated computation of two-loop integrands is described. The algorithm covers all the steps of the computation, from the generation of loop topologies up to the construction of recursion relations for two loop integrands. Finally, first steps towards the formulation of a new approach for reducing two-loop amplitudes to a basis of master integrals are discussed.

hep-ph↗

arXiv2011

Top quark pair production in association with a Z-boson at NLO accuracy

We present predictions for the production cross section of t-quark pair production in association with a Z boson at the next-to-leading order (NLO) accuracy using matrix elements obtained from the HELAC-Oneloop package. We use the subtraction method for computing the radiative corrections as implemented in the POWHEG-Box, which was also used in several other computations of similar complexity.

hep-ph↗

arXiv2011

Top quark pair production in association with a jet with NLO parton showering

We compute the production cross section of a top-antitop pair in association with a jet at hadron colliders at next-to-leading order accuracy matched with parton shower algorithms to make predictions at the hadron level. The parton shower allows for including the decay of the top quarks at the leading order accuracy. We use a framework based on three well established numerical codes, the POWHEG-BOX, used for the calculation of the cross section, HELAC, which generates the matrix elements for the Born-level, real emission and the virtual part, and finally a parton shower program, such as PYTHIA or HERWIG, which generate the parton-shower and hadronization.

hep-ph↗