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Abstract: Based on the OPP technique and the HELAC framework, HELAC-1LOOP is a program that is capable of numerically evaluating QCD virtual corrections to scattering amplitudes. A detailed presentation of the algorithm is given, along with instructions to run the code and benchmark results. The program is part of the HELAC-NLO framework that allows for a complete evaluation of QCD NLO corrections. Program summary: Program title: HELAC-1LOOP Catalogue identifier: AEOC_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEOC_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 290945 No. of bytes in distributed program, including test data, etc.: 3013326 Distribution format: tar.gz Programming language: Fortran (gfortran(http://gcc.gnu.org/fortran/), lahey95 (http://www.lahey.com), ifort3(http://software.intel.com)). Computer: Any. Operating system: Linux, Unix, Mac OS. Classification: 11.1. Nature of problem: The evaluation of virtual one-loop amplitudes for multi-particle scattering is a long-standing problem [1]. In recent years the OPP reduction technique [2] opened the road for a fully numerical approach based on the evaluation of the one-loop amplitude for well-defined values of the loop momentum. Solution method: By using HELAC [3–5] and CutTools [6], HELAC-1LOOP is capable of evaluating QCD virtual corrections [7]. The one-loop -particle amplitudes are constructed as part of the tree-order ones, by using the basic recursive algorithm used in HELAC. A Les Houches Event (LHE) file is produced, combining the complete information from tree-order and virtual one-loop contributions. In conjunction with real corrections, obtained with the use of HELAC-DIPOLES [8], the full NLO corrections can be computed. The program has been successfully used in many applications. Running time: Depending on the number of particles and generated events from seconds to days. References: [[1]] R.K. Ellis, Z. Kunszt, K. Melnikov and G. Zanderighi, arXiv:1105.4319[hepph]. [[2]] G. Ossola, C. G. Papadopoulos and R. Pittau, Nucl. Phys. B 763 (2007) 147 [arXiv:hep-ph/0609007]. [[3]] A. Kanaki and C. G. Papadopoulos, Comput. Phys. Commun. 132 (2000) 306 [arXiv:hep-ph/0002082]. [[4]] C. G. Papadopoulos, Comput. Phys. Commun. 137 (2001) 247 [arXiv:hepph/ 0007335]. [[5]] A. Cafarella, C. G. Papadopoulos and M. Worek, Comput. Phys. Commun. 180 (2009) 1941 [arXiv:0710.2427 [hep-ph]]. [[6]] G. Ossola, C. G. Papadopoulos and R. Pittau, JHEP 0803 (2008) 042 [arXiv:0711.3596 [hep-ph]]. [[7]] A. van Hameren, C. G. Papadopoulos and R. Pittau, JHEP 0909, 106 (2009) [arXiv:0903.4665 [hep-ph]]. [[8]] M. Czakon, C. G. Papadopoulos and M. Worek, JHEP 0908, 085 (2009) [arXiv:0905.0883 [hep-ph]]. [Copyright &y& Elsevier]

Achieving a precise description of multi-parton final states is crucial for many analyses at LHC. In this contribution we review the main features of the HELAC-NLO system for NLO QCD calculations. As a case study, NLO QCD corrections for jet production at LHC are illustrated and discussed. [ABSTRACT FROM AUTHOR]

Abstract: This paper describe a package written in MATHEMATICA that automatizes typical operations performed during evaluation of Feynman graphs with Mellin–Barnes (MB) techniques. The main procedure allows to analytically continue a MB integral in a given parameter without any intervention from the user and thus to resolve the singularity structure in this parameter. The package can also perform numerical integrations at specified kinematic points, as long as the integrands have satisfactory convergence properties. It is demonstrated that, at least in the case of massive graphs in the physical region, the convergence may turn out to be poor, making naïve numerical integration of MB integrals unusable. Possible solutions to this problem are presented, but full automatization in such cases may not be achievable. Program summary: Title of program: MB Program summary URL: http://cpc.cs.qub.ac.uk/summaries/ADYG_v1_0 Catalogue identifier: ADYG_v1_0 Program obtainable from: CPC Program Library, Queen''s University of Belfast, N. Ireland Computers: All Operating systems: All Programming language used: MATHEMATICA, Fortran 77 for numerical evaluation Memory required to execute with typical data: Sufficient for a typical installation of MATHEMATICA. No. of lines in distributed program, including test data, etc.: 12 013 No. of bytes in distributed program, including test data, etc.: 231 899 Distribution format: tar.gz Libraries used: CUBA [T. Hahn, Comput. Phys. Commun. 168 (2005) 78] for numerical evaluation of multidimensional integrals and CERNlib [CERN Program Library, obtainable from: http://cernlib.web.cern.ch/cernlib/] for the implementation of Γ and ψ functions in Fortran. Nature of physical problem: Analytic continuation of Mellin–Barnes integrals in a parameter and subsequent numerical evaluation. This is necessary for evaluation of Feynman integrals from Mellin–Barnes representations. Method of solution: Recursive accumulation of residue terms occurring when singularities cross integration contours. Numerical integration of multidimensional integrals with the help of the CUBA library. Restrictions on the complexity of the problem: Limited by the size of the available storage space. Typical running time: Depending on the problem. Usually seconds for moderate dimensionality integrals. [Copyright &y& Elsevier]

A review of the calculation of the two loop bosonic corrections to Δr is presented. Factorization and matching onto the Fermi model are discussed. An approximate formula, describing the quantity over the interesting range of Higgs boson mass values from 100 GeV to 1 TeV is given. [Copyright &y& Elsevier]

A self-consistent version of the left-right (LR) symmetric model is used to examine tree- as well as one-loop level radiative corrections to the muon decay. It is shown that constraints on the heavy sector of the model parameters are different when going beyond tree-level physics. In fact, in our case, the only useful constraints on the model can be obtained from the one-loop level calculation. Furthermore, corrections coming from the subset of SM particles within the LR model have a different structure from their SM equivalent, e.g. the top quark leading term contribution to Δϱ within the LR model is different from its SM counterpart. As a consequence, care must be taken in fitting procedures of models beyond the SM, where usually, only tree-level couplings modified by the SM radiative corrections are considered. This procedure is not always correct. [Copyright &y& Elsevier]

Abstract: ZFITTER is a Fortran program for the calculation of fermion pair production and radiative corrections at high energy colliders; it is also suitable for other applications where electroweak radiative corrections appear. ZFITTER is based on a semi-analytical approach to the calculation of radiative corrections in the Standard Model. We present a summary of new features of the ZFITTER program version 6.42 compared to version 6.21. The most important additions are: (i) some higher-order QED corrections to fermion pair production, (ii) electroweak one-loop corrections to atomic parity violation, (iii) electroweak one-loop corrections to production, (iv) electroweak two-loop corrections to the W boson mass and the effective weak mixing angle. Program summary: Title of program: ZFITTER version 6.42 (18 May 2005) Catalogue identifier:ADMJ_v2_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/ADMJ_v2_0 Authors of original program: D. Bardin, P. Christova, M. Jack, L. Kalinovskaya, A. Olshevski, S. Riemann, T. Riemann Program obtainable from: CPC Program Library, Queen''s University of Belfast, N. Ireland Reference for ZFITTER version 6.21: D. Bardin et al., Comput. Phys. Comm. 133 (2001) 229–395 Operating system: UNIX/LINUX, program tested under, e.g., HP-UX and PC/Linux Programming language used: FORTRAN 77 High speed storage required: <2 MB No. of lines in distributed program, including test data, etc.:29 164 No. of bytes in distributed program, including test data, etc.:185 824 Distribution format:tar.gz Does the new version supersede the previous version:Yes Nature of the physical problem: Fermion pair production is an important reaction for precision tests of the Standard Model, at LEP/SLC and future linear colliders at higher energies. For this purpose, QED, electroweak and QCD radiative corrections have to be calculated with high precision, including higher order effects. Multi parameter fits used to extract model parameters from experimental measurements require a program of sufficient flexibility and high calculational speed. ZFITTER combines these two aspects by employing analytical integrations of matrix elements and at most one-dimensional numerical integration, as well as a variety of flags defining the physics content used. The calculated predictions are typically at the per mille precision level, sometimes better. Method of solution: Numerical integration of analytical formulae. Reasons for new version:Addition of substantial material into the code: covering of more reactions; more accurate description of existing reactions. Summary of revisions:New parts for predicting atomic parity violation and for neutrino pair production; more accurate higher order QED corrections for fermion pair production; two-loop corrections to the predictions of W mass and of the weak mixing angle. Restrictions on the complexity of the problem: Fermion pair production is described below the top quark pair production threshold. Photonic corrections are taken into account with simple cuts on photon energy, or the energies and acollinearity of the two fermions, and one fermion production angle. The treatment of Bhabha scattering is less advanced. Typical running time: On a Pentium IV PC installation (2.8 GHz) using g77 under Linux 2.4.21, approximately 23 s are needed to run the standard test of subroutine ZFTEST. This result is for a default/recommended setting of the input parameters, with all corrections in the Standard Model switched on. ZFTEST computes 12 cross-sections and cross-section asymmetries for 8 energies with 5 interfaces, i.e. about 360 cross-sections in 23 s. [Copyright &y& Elsevier]