NGAMMA: A Monte Carlo generator for multiphoton production in e+e− annihilation

We present the NGAMMA Monte Carlo event generator for QED processes of e+e- annihilation into a multiphoton final state, e+e- → Nγ(N ≥ 2). These processes are an important source of background in the study of e+e- → hadrons processes with a multiphoton final state, especially for experiments at low energy e+e- colliders like SND, CMD-3, KLOE and for the BESIII experiment. For generation, NGAMMA exploits the exact tree-level amplitude.