EKHARA 3.0: An update of the EKHARA Monte Carlo event generator

Abstract

The Monte Carlo event generator EKHARA was upgraded during last years. The upgrades presented here contain: (a) the inclusion of new final states e+e−→e+e−η, e+e−→e+e−η′, e+e−→e+e−χci and e+e−→e+e−χci(→J∕ψ(→μ+μ−)γ); b) new γ∗−γ∗−P transition form factors and c) the radiative corrections to the reactions e+e−→e+e−P. For the upgrades (a) and (b), we present here only the pieces missing in other publications, mostly algorithms used in the phase space generation. The radiative corrections are presented here for the first time. A new algorithm of the phase space generation for the reaction e+e−→e+e−Pγ being its main part. A comparison with GGRESRC generator is presented. Big differences between the radiative corrections calculated by the EKHARA and the GGRESRC generators are observed. New version program summaryProgram Title: EKHARA 3.0Program Files doi:http://dx.doi.org/10.17632/g5nmv83g5z.1Licensing provisions: GPLv3Programming language: FORTRAN 77Supplementary material: The following publications are relevant for the upgrades presented in Section 2: [3,4,5,6]Journal reference of previous version: H. Czyż, S. Ivashyn, Comput. Phys. Commun. 182 (2011) 1338.Does the new version supersede the previous version?: YesReasons for the new version: Major upgrades.Summary of revisions: The upgrades contain the inclusion of the new final states e+e−→e+e−η, e+e−→e+e−η′, e+e−→e+e−χci and e+e−→e+e−χci(→J∕ψ(→μ+μ−)γ), new γ∗−γ∗−P transition form factors and the radiative corrections to the reactions e+e−→e+e−P.Nature of problem: The program is constructed to help in measurements of transition form factors at meson factories. To do this one needs a good description of the already existing data and calculation of the radiative corrections.Solution method: The models of various form factors were developed in [3,4,5,6] and are implemented in the program. For the radiative corrections a new algorithm of generation of the phase space for the reactions e+e−→e+e−Pγ was developed and is presented here.Additional comments including Restrictions and Unusual features: The program needs a quadruple precision version of a FORTRAN compiler.