GALUGA

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 γ * γ * structure functions now include several ansätze 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 .