TPEcalc: a program for calculation of two-photon exchange amplitudes

TPEcalc is a C++ program for calculation of two-photon exchange (TPE) amplitudes in elastic electron-hadron scattering, based on the dispersion method. It is a command-line tool which accepts kinematical parameters (Q^2 and epsilon) as input and returns TPE amplitudes. It can do calculations for proton, neutron and pion targets. Any spin 1/2+ or spin 0- target is supported, if the user supplies all necessary form factor parameterizations. This paper describes how to use TPEcalc and outlines underlying theory. The program source code can be downloaded from http://tpe.bitp.kiev.ua/