SANCnews: Sector [formula omitted

Abstract

In this paper we describe the implementation of processes f 1 f ¯ 1 Z Z → 0 and f 1 f ¯ 1 H Z → 0 into the framework of SANC system. The f 1 stands for a massless fermion f whose mass is kept non-zero only in arguments of ln functions and →0 means that all 4-momenta flow inwards. The derived scalar form factors can be used for any cross channel after an appropriate permutation of their arguments ( s , t , u ). We present the covariant and helicity amplitudes for these processes: for the former only in the annihilation channel f 1 f ¯ 1 → Z Z , while for the latter in annihilation f 1 f ¯ 1 → H Z and decay H → Z f 1 f ¯ 1 channels. We briefly describe additional precomputation modules which were not covered in the previous paper. For the processes f 1 f ¯ 1 → H Z ( Z Z ) and decay H → Z f 1 f ¯ 1 we present compact results of calculation of the accompanying bremsstrahlung and discuss exhaustive numerical results. As applications there are two types of the Monte Carlo generators for the process H → 4 μ . The first one is the generator based on a single resonance approximation for one of the Z bosons. The second one, exploiting the double resonance approximation, is not described in this article. For the generator in the single approximation we present a short description. Whenever possible, we compare our results with those existing in the literature. For example, we present a comparison of the results for H → 4 μ decay with those obtained by MC generator Prophecy4f. SANC client for version v.1.10 can be downloaded from servers at CERN http://pcphsanc.cern.ch/ and Dubna http://sanc.jinr.ru/. Program summary Program title: SANC Catalogue identifier:ADXK_v1_1 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/ADXK_v1_1.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.:23 274 No. of bytes in distributed program, including test data, etc.: 1 691 761 Distribution format:tar.gz Programming language:Java, FORM3, PERL, FORTRAN Computer:Intel-based PCs on which Java and FORM3 are available Operating system:Linux, Windows RAM:10 MB Word size:32 Classification:11.6 Does the new version supersede the previous version?:Yes Nature of problem:Automatic calculation of pseudo- and realistic observables for various processes and decays in the Standard Model of Electroweak interactions, QCD and QED at one-loop precision level. Form factors and helicity amplitudes free of UV divergences are produced. For exclusion of IR singularities the soft photon emission is included. Solution method:Numerical computation of analytical formulae of form factors and helicity amplitudes. For simulation of two fermion radiative decays of Standard Model bosons ( W ± , Z ) and the Higgs boson a Monte Carlo technique is used. Reasons for new version:Implementation of new processes; extension of an automatic generation of FORTRAN codes by the s2n.f package onto many more processes; bug fixes. Summary of revisions:Implementation of light-by-light scattering into QED branch; vast update of 2f2b node in EW branch; complete renovation of QCD branch. Restrictions:In the current version of SANC there are 3 and 4 particle processes and decays available at one-loop precision level. Running time:The running time depends on the selected process. For instance, the symbolic calculation of form factors (with precomputed building blocks) for H → e + e − Z process takes about 10 sec, helicity amplitudes—about 10 sec, and bremsstrahlung—1 min 10 sec. The relevant s2n runs take about 2 min 40 sec, 1 sec and 30 sec, respectively. The numerical computation of decay rate for this process (production of benchmark case 3 Table) takes about 5 sec (CPU 3 GHz IP4, RAM 512 Mb, L2 1024 KB).