KEKB (accelerator)

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KEKB is the name of the accelerator used in the Belle Experiment to study CP violation. It is called a B-factory for its copious production of B-mesons which provide a golden mode to study and measure the CP violation due to its property of decaying into other lighter mesons. KEKB is basically an asymmetric electron–positron collider, with electrons having the energy of 8 GeV and positrons having the energy of 3.5 GeV, giving 10.58 GeV centre-of-mass energy, which is equal to the mass of Upsilon(4S).

There are basically two rings for accelerating electrons and positrons. The ring for electrons, having energy of 8 GeV, is called the high-energy ring (HER), while the ring for positrons, having energy of 3.5 GeV, is called low-energy ring (LER). The HER and LER are constructed side-by-side in the tunnel. The circumference of each ring is 3016 m, having four straight sections. In the KEKB, there is only one interaction point in the Tsukuba. KEKB is located at the High Energy Accelerator Research Organisation (KEK) in Tsukuba, Ibaraki Prefecture, Japan.

Since the energy of the electrons & positrons is asymmetric, the B meson pairs are created with a Lorentz boost factor of 0.425.