Harman Patil (Editor)

Belle experiment

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The Belle experiment is a particle physics experiment conducted by the Belle Collaboration, an international collaboration of more than 400 physicists and engineers investigating CP-violation effects at the High Energy Accelerator Research Organisation (KEK) in Tsukuba, Ibaraki Prefecture, Japan.

The Belle detector, located at the collision point of the
e−

e+
 asymmetric-energy collider (KEKB), is a multilayer particle detector. Its large solid angle coverage, vertex location with precision on the order of tens of micrometres (provided by a silicon vertex detector), good pion–kaon separation at the momenta range from 7002100000000000000♠100 MeV/c till few GeV/c (provided by a novel Cherenkov detector), and few-percent precision electromagnetic calorimetry (CsI(Tl) scintillating crystals) allow for many other scientific searches apart from CP-violation. Extensive studies of rare decays, searches for exotic particles and precision measurements of B mesons, D mesons, and tau particles have been carried out and have resulted in almost 300 publications in physics journals.

Highlights of the Belle experiment so far include

  • the first observation of CP-violation outside of the kaon system (2001)
  • observation of: B → K ∗ l + l − and b → s l + l −
  • measurement of ϕ 3 using the B → D K , D → K S π + π − Dalitz plot
  • measurement of the CKM quark mixing matrix elements | V u b | and | V c b |
  • observation of direct CP-violation in B 0 → π + π − and B 0 → K − π +
  • observation of b → d transitions
  • evidence for B → τ ν
  • observations of a number of new particles including the X(3872)

    • The Belle experiment operated at the KEKB accelerator, the world's highest luminosity machine. The instantaneous luminosity exceeded 7034210999999999999♠2.11×1034 cm−2·s−1. The integrated luminosity collected at the
    ϒ
    (4S) resonance mass is ~7002710000000000000♠710 fb−1 (corresponds to 771 million
    B

    B
     meson pairs). Most data is recorded on the
    ϒ
    (4S) resonance, which decays to pairs of B mesons. About 10% of the data is recorded below the
    ϒ
    (4S) resonance in order to study backgrounds. In addition, Belle has carried out special runs at the
    ϒ
    (5S) resonance to study
    B
    s     mesons as well as on the
    ϒ
    (1S),
    ϒ
    (2S) and
    ϒ
    (3S) resonances to search for evidence of Dark Matter and the Higgs Boson. The samples of
    ϒ
    (1S),
    ϒ
    (2S) and
    ϒ
    (5S) collected by Belle are the world largest samples available.

    The Belle II B-factory, an upgraded facility with two orders of magnitude more luminosity, has been approved in June 2010. The design and construction work is ongoing.

    References

    Belle experiment Wikipedia
    (Text) CC BY-SA