Two-photon physics with GALUGA 2.0

An extended version of the Monte Carlo program GALUGA is presented for the computation of two-photon production in e(+)e(-) collisions. Functions implemented for the five gamma(star)gamma(star) structure functions now include several ansatze of the total hadronic cross section based on the BFKL Pomeron and various Regge-like models. In addition, structure functions for resonance formation are included with full dependence on the two-photon virtualities Q(1)(2) and Q(2)(2) as given in the constituent-quark model. The six lowest-lying resonances of each of the C-even mesons with J(P) = 0(-), 0(+), 1(+), 2(+) and 2(-) are provided. The program can also be used to calculate with exact kinematics the effective two-photon luminosity function. Special emphasis is put on a numerically stable evaluation of all variables over the full Q(i)(2) range while keeping all dependences on the electron mass and Q(i)(2). (C) 1998 Published by Elsevier Science B.V.