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In particle physics, a B-factory, or sometimes a beauty factory,〔 〕 is a collider-based scientific machine designed to produce a large number (of the order of 109) of B mesons and analyze their properties. Tauons and D mesons are also copiously produced at B-factories, which allows precise studies of their properties. Two B-factories were designed and built in the 1990s. They are both based on electron-positron colliders with the centre of mass energy tuned to the ϒ(4S) resonance peak, which is just above the threshold for decay into two B mesons (both experiments took smaller data samples at different centre of mass energies). The Belle experiment at the KEKB collider in Tsukuba, Japan, and the BaBar experiment at the PEP-II collider at SLAC laboratory in California, USA, completed data collection in 2010 and 2008, respectively.〔http://www-conf.slac.stanford.edu/babardandd/Documents/DND_Safety_MARrevisionFO2009v4.pdf〕 The B-factories yielded a rich harvest of results, including the first observation of CP violation outside of the kaon system, measurements of the CKM parameters |''V''ub| and |''V''cb|, and measurements of purely leptonic B meson decays. Proposals for next-generation B-factories include the canceled SuperB designed to be built in Frascati near Rome in Italy, and Belle II in Japan. ==See also== * *HERA-B 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「B-factory」の詳細全文を読む スポンサード リンク
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