Limitation on the luminosity of e+e− storage rings due to beamstrahlung

Particle loss due to the emission of single energetic beamstrahlung photons in beam collisions is shown to impose a fundamental limit on storage-ring luminosities at energies greater than 2E0 ∼ 140GeV for head-on collisions and 2E0 ∼ 40GeV for crab-waist collisions. Above these threshold energies, the suppression factor due to beamstrahlung scales as 1/E 0 , and for a fixed power of synchrotron radiation, the luminosity L ∝ R/E 0 , where R is the collider radius. For 2E0 & 150GeV, both collision schemes have similar luminosity limits. The luminosities attainable at storage-ring and linear-collider (LC) 2E0 ∼ 240GeV Higgs factories are comparable; at higher energies, LCs are preferable. This conference paper is based on my recent PRL publication [1] supplemented with additional comments on linac-ring e+e− colliders and ring e+e− colliders with