Disruption effects from the interaction of rounde+e−beams

We report on our recent simulation results on the disruption effects during the interaction of round $e^{+}$ $e^{\mathrm{-}}$ beams in linear colliders. It is found that in addition to the well-known disruption parameter D, the disruption effects also depend on another parameter A≡${\sigma }_z$/${\beta }^{\mathrm{*}}$, where ${\sigma }_z$ is the bunch length and ${\beta }^{\mathrm{*}}$ the β function at the interaction point. It turns out that while the luminosity enhancement factor $H_D$ is insensitive to A only in the small-D (D≲1) regime, the disruption-angle enhancement factor $H_{\theta }$ behaves oppositely. Specifically, we found that for large D, $H_{\theta }$ is suppressed as 1/ √D , and $H_D$ increases monotonically without saturation. Moreover, for fixed D, $H_D$ varies as a function of ln(1/A). Computer analysis further suggests that in the large-D and small-A regime a confinement mechanism is developed near the beginning of the collision: particles once pinched tend to be trapped in a much smaller radius throughout the process. A theoretical model is provided to qualitatively explain the above findings.