B race hots up

15 March 2000

The new generation of “B-factory” electron-positron colliders at SLAC, Stanford (PEP-II), and the Japanese KEK laboratory (KEKB) have both made good progress and exceeded luminosities (a measure of the collision rate) of 1033/cm2/s – previously uncharted territory for electron-positron colliders. PEP-II achieved this figure late last year and KEKB reached it in February.

PEP-II achieved its first collisions in July 1998, but the BaBar physics detector did not appear until May 1999. KEKB and its BELLE detector began operation last June. The aim of these colliders is to mass-produce B particles (containing the fifth “b” quark), and the new collision rates are good news for the physicists, who hope to see the first signs of CP violation in a B particle setting.

The previous world record electron-positron luminosity was 8 x 1032, held by the valiant CESR ring at Cornell, which is still in the race. CERN’s 27 km LEP collider is in a different league because of its size, and here the focus is on achieving maximum collision energy.

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