Energy Resolution at Interaction Point for Asymmetric Beams

The monochromatic scheme adopted in the tau-charm factories uses a large dispersion at interaction point to obtain a very high collision energy resolution. Due to the presence of dispersion, however, the beambeam interaction induces the synchro-betatron coupling. Even if in the linear regime, it can lead to potentially serious effects. One of the most serious is the rapid decrease of the energy resolution when the beam-beam parameter increases, even if the motion is stable. In this paper we study this effect in detail either for symmetric and asymmetric beams and give formula for the energy resolution.