Monochromatization of $e^+e^-$ colliders with a large crossing angle

Abstract

The relative center-of-mass energy spread at $e^+e^-$ colliders is about $10^{-3}$, which is much larger than the widths of narrow resonances J/$\psi$, $\psi$(2S), $\Upsilon$(1S), $\Upsilon$(2S), $\Upsilon$(3S) mesons, tauonium and some others. It's reduction would significantly increase the resonance production rates and open up great opportunities in the search for new physics. In this paper, we propose a new monochromatization method for colliders with a large crossing angle (which can provide a high luminosity). The contribution of the beam energy spread to the spread of the center-of-mass energy is canceled by introducing an appropriate energy-angle correlation at the interaction point; $\sigma_W/W \sim (0.5-1)10^{-5}$ appears possible.