KEK B-Factory Project
 
KEK B-Factory Project aims at solving the long-standing puzzle of elementary particles ; there is a subtle imbalance in physics law between particles and their antiparticles (CP violation). On the other hand, there is a huge imbalance between matter and antimatter in the universe ; an antimatter world does not seem to exist. The B-Factory project is expected to give a clue to answer such questions, too.

An experimental key to the CP problem lies in the third-generation quark, the bottom quark. An asymmetric electron-positron collider (KEKB) is under construction as a means to selectively mass-produce high-energy B-antiB meson pairs, where a B is a meson made of a b-quark and a lighter quark. To measure such final states, a general-purpose detector (BELLE) is being built. It is used to quantify differences between decays of B and antiB mesons and also to study all aspects of b-quarks at unprecedentedly deep levels.

The new collider, KEKB, is built in the TRISTAN tunnel which is 3 km in circumference. A 3.5 GeV positron beam crosses with an 8 GeV electron beam at a shallow angle of 11 mrad. In order to achieve an ultimate collision luminosity of 1034/cm2/sec, very high beam currents are distributed over 5,000 bunches going around the collider rings. The beams are stably accelerated with newly developed superconducting as well as normal conducting RF cavities and are further stabilized with a feedback system.

ARES Normal conducting accelerating cavity with energy storage. Large tank at left is the energy storage cell.	Quadrupole magnets for LER placed in the TRISTAN tunnel

The new detector, BELLE, is being constructed by a large collaboration of physicists from 10 countries/regions. It can perform accurate particle tracking in 1.5 Tesla magnetic field and is equipped with fine-grained calorimeter for high precision gamma-ray measurement.
Good particle identification capability is provided by advanced Time-of-Flight counters as well as new aerogel Cherenkov counters. Data acquisition system allows a very high-rate data collection with parallel processing.

BELLE detector structure under construction Cryostat of superconducting magnet is about to be installed.	Central Drift Chamber

Commissioning of the project is scheduled to be in the fall of 1998, both for KEKB and BELLE. The experiment will start by the beginning of 1999.