Monochromatization of e+e− colliders with a large crossing angle

The relative center-of-mass energy spread [Formula: see text] at [Formula: see text] colliders is [Formula: see text], which is much larger than the widths of narrow resonances [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] mesons, tauonium and some others. Its 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 [Formula: see text] is canceled by introducing an appropriate energy–angle correlation at the interaction point; [Formula: see text] appears possible.