GaGaRes: A Monte Carlo generator for resonance production in two-photon physics

In this paper a Monte Carlo generator, GaGaRes, is presented which can be used to describe two-photon resonance production in e+e− collisions. The program can generate the five lowest-lying C=+1 meson states of any qq̄ combination together with the outgoing electron and positron. The dependence on the photon virtualities Q1 and Q 2 2 is fully taken into account. The program also generates the density matrices of the resonance, which form an essential tool in the description of the decay of the resonances. Furthermore, the program is applicable for all tagging conditions. PROGRAM SUMMARY Title of program: GaGaRes Program obtainable from: CPC Library Computer for which the program is designed and others on which it is operable: Any computer that runs under UNIX and can handle quadruple precision numbers (both real and complex). FORTRAN 90 offers the possibility to define own data types. This should be used on systems where complex numbers are not available in quadruple precision. Operating system under which the program has been tested : UNIX Programming language used : FORTRAN 90 Number of lines: 6009 (including comments)