B, τ Charm, and φ Factories

Electron-positron collider type particle factories, B-Factory, τ Charm Factory, and φ Factory, aim at achieving a high luminosity in a range of 5x1032 cm-2s-1 to 1034 cm-2s-1. This goal requires storing large currents, 0.5 A to 5 A, in rings by distributing them into large number of bunches. To avoid unnecessary collisions, all factories adopt two-ring scheme, where electrons and positrons are stored in different rings. One φ Factory, DAΦNE is now being commissioned and two asymmetric-energy B-Factories, KEKB and PEP-II, now under construction, will be completed by the end of 1998. IHEP, Beijing, expects R and D of its τ Charm Factory, BTCF, to be approved soon. (author)