Achievements of KEKB

Prog. Theor. Exp. Phys. 2013, 03A001 (18 pages) DOI: 10.1093/ptep/pts102 KEKB Accelerator Achievements of KEKB 1 KEK, High Energy Accelerator Organization, Oho 1-1, Tsukuba, Ibaraki 305-0801, Japan SLAC National Accelerator Laboratory, Stanford University, Menlo Park, CA 94025, USA 3 The Budker Institute of Nuclear Physics, Academician Lavrentyev 11, 630090 Novosibirsk, Russia 4 Institute for High Energy Physics, Beijing, China 5 CERN, European Organization for Nuclear Research, CH-1211 Geneva 23, Switzerland ∗ E-mail: 2 Received September 18, 2012; Accepted December 25, 2012; Published March 26, 2013 ............................................................................... The machine commissioning of KEKB started in December 1998 and its operation was terminated at the end of June 2010 to upgrade KEKB to SuperKEKB. In this paper, we summarize the history of KEKB and show the achievements made there. ............................................................................... © The Author(s) 2013. Published by Oxford University Press on behalf of the Physical Society of Japan. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Tetsuo Abe1 , Kazunori Akai1 , Norimasa Akasaka1 , Mitsuo Akemoto1 , Atsuyoshi Akiyama1 , Mitsuhiro Arinaga1 , Yunhai Cai2 , Kiyokazu Ebihara1 , Kazumi Egawa1 , Atsushi Enomoto1 , Eiji Ezura1 , John Flanagan1 , Shigeki Fukuda1 , Hitoshi Fukuma1 , Yoshihiro Funakoshi1,∗ , Kazuro Furukawa1 , Takaaki Furuya1 , Junji Haba1 , Kazufumi Hara1 , Toshiyasu Higo1 , Shigenori Hiramatsu1 , Hiromi Hisamatsu1 , Hiroyuki Honma1 , Teruya Honma1 , Kenji Hosoyama1 , Takao Ieiri1 , Naoko Iida1 , Hitomi Ikeda1 , Mitsuo Ikeda1 , Shigemi Inagaki1 , Shigeru Isagawa1 , Hitoshi Ishii1 , Atsushi Kabe1 , Eiichi Kadokura1 , Tatsuya Kageyama1 , Kazuhisa Kakihara1 , Eiji Kako1 , Susumu Kamada1 , Takuya Kamitani1 , Ken-ichi Kanazawa1 , Hiroaki Katagiri1 , Shigeki Kato1 , Takashi Kawamoto1 , Sergey Kazakov1 , Mitsuo Kikuchi1 , Eiji Kikutani1 , Kiyoshi Kitagawa1 , Haruyo Koiso1 , Yuuji Kojima1 , Ichitaka Komada1 , Tadashi Kubo1 , Kikuo Kudo1 , Shin-ichi Kurokawa1 , Katsumi Marutsuka1 , Mika Masuzawa1 , Shuji Matsumoto1 , Toshihiro Matsumoto1 , Shinichiro Michizono1 , Katsuhiko Mikawa1 , Toshihiro Mimashi1 , Toshiyuki Mitsuhashi1 , Shinji Mitsunobu1 , Takako Miura1 , Kenji Mori1 , Akio Morita1 , Yoshiyuki Morita1 , Hirotaka Nakai1 , Hiromitsu Nakajima1 , Tatsuro T. Nakamura1 , Hiroshi Nakanishi1 , Kota Nakanishi1 , Katumi Nakao1 , Hisayoshi Nakayama1 , Michiru Nishiwaki1 , Yujiro Ogawa1 , Kazuhito Ohmi1 , Yukiyoshi Ohnishi1 , Satoshi Ohsawa1 , Yasunobu Ohsawa1 , Norihito Ohuchi1 , Katsunobu Oide1 , Toshiyuki Oki1 , Masaaki Ono1 , Toshiyuki Ozaki1 , Eugene Perevedentsev3 , Hiroshi Sakai1 , Yutaka Sakamoto1 , Masayuki Sato1 , Kotaro Satoh1 , Masanori Satoh1 , Yuji Seimiya1 , Kyo Shibata1 , Tetsuo Shidara1 , Miho Shimada1 , Samo Stanic1 , Mitsuru Shirai1 , Akihiro Shirakawa1 , Tsuyoshi Sueno1 , Masaaki Suetake1 , Yusuke Suetsugu1 , Ryuhei Sugahara1 , Takashi Sugimura1 , Tsuyoshi Suwada1 , Osamu Tajima1 , Susumu Takano1 , Seiji Takasaki1 , Tateru Takenaka1 , Yasunao Takeuchi1 , Yasunori Takeuchi1 , Masafumi Tawada1 , Masaki Tejima1 , Makoto Tobiyama1 , Noboru Tokuda1 , Kiyosumi Tsuchiya1 , Sadaharu Uehara1 , Shoji Uno1 , Yingzhi Wu4 , Noboru Yamamoto1 , Yasuchika Yamamoto1 , Yoshiharu Yano1 , Kazue Yokoyama1 , Masato Yoshida1 , Mitsuhiro Yoshida1 , Shin-ichi Yoshimoto1 , Kazuo Yoshino1 , Masakazu Yoshioka1 , Demin Zhou1 , Frank Zimmermann5 , and Zhanguo Zong1 PTEP 2013, 03A001 1. T. Abe et al. Introduction KEKB is a two-ring, asymmetric-energy, electron–positron collider constructed at KEK with the aim of producing B mesons as in a factory. The construction of KEKB started in 1994, utilizing the existing tunnel of TRISTAN, a 30 GeV × 30 GeV electron–positron collider. The machine commissioning of KEKB started in December 1998. The physics experiment with the physics detector named Belle was started in June 1999. The peak luminosity surpassed the design value of 1.0 × 1034 cm−2 s−1 in May 2003. The maximum peak luminosity of KEKB is 2.11 × 1034 cm−2 s−1 , which was recorded in June 2009. This value has been the world record since then. The KEKB operation was terminated at the end of June 2010 to upgrade KEKB to SuperKEKB. The total integrated luminosity collected by the Belle detector was 1041 fb−1 . The history of KEKB is shown in Fig. 1. The most important outcome of the physics experiment at KEKB/Belle is the detection of CP violation in B mesons predicted on the basis of the Kobayashi–Maskawa theory. Prof. M. Kobayashi and Prof. T. Maskawa were awarded the 2008 Nobel Prize in Physics for this theory. The Belle experiment, carried out using KEKB, contributed greatly to confirmation of the theory. Features of KEKB In this section, we describe the design of KEKB and its features. 2.1. General scheme The design concepts of KEKB are reported in the KEKB design report [1]. Figure 2 shows the schematic layout of KEKB. In Table 1, the machine parameters of KEKB with which the record peak luminosity was achieved on 7 June 2009 are summarized. The design parameters of KEKB are also shown in the table in parentheses. This table shows some basic features of KEKB. First of all, KEKB is an energy-asymmetric collider. Although it is mostly operated on the ϒ(4S) resonance like CESR-B, the energies of the two beams are different. This asymmetry comes from the physics motivation. The low energy ring (LER) is for the positron beam and the high energy ring (HER) is for the electron beam. This choice of charge was made considering the ion effects (the fast ions and the trapped ions) in the electron ring and the situation of the injector upgrade to realize direct injection. The second feature is a high design luminosity of 1 × 1034 cm−2 s−1 . To realize this luminosity, we chose the following design parameters: ◦ Very low β y∗ : 1 cm for both beams ◦ Very high beam currents: 1.1 A for electrons and 2.6 A for positrons ◦ Relatively high beam–beam parameters: 0.052 in the vertical plane. 2.2. Energy transparency As seen in Table 1, we assumed so-called energy transparency conditions in the design in order to balance the beam–beam effects between the two beams with different energies. We assumed that the beta functions at the IP, the beam–beam parameters, the radiation damping time, the emittances, the synchrotron tune, and the (fractional part of the) betatron tunes are the same for the two beams. To equalize the radiation damping time, wiggler magnets were installed in the LER. As a result of these, the design beam currents are inversely proportional to the beam energy. 2/18 2. PTEP 2013, 03A001 T. Abe et al. 2.3. IR design We introduced a (...truncated)