Photon radiation in $e^{+}{e}^{-}\to$ hadrons at low energies with CARLOMAT 3.1

Abstract

We present a sample of results for the cross sections of several processes of low energetic $e^{+}{e}^{-}$ annihilation into final states containing pions accompanied by one or two photons, or a light lepton pair. The results, which have been obtained with a new version of a multipurpose Monte Carlo program CARLOMAT, labelled 3.1, demonstrate new capabilities of the program which, among others, include a possibility of taking into account either the initial or final state radiation separately, or both at a time, and a possibility of inclusion of the electromagnetic charged pion form factor for processes with charged pion pairs. We also discuss some problems related to the $U(1)$ electromagnetic gauge invariance.

Comments: 17 pages, 17 figures, matches version published in Eur. Phys. J. C