Belle experiment

Coordinates: 36 ° 9 ′ 28 ″  N , 140 ° 4 ′ 30 ″  E

The Belle detector at KEKB .

The Belle experiment was located at the Japanese Research Center for Particle Physics KEK and dealt with B physics . From 1999 to 2010 a total of 772 million decays of B mesons were recorded and analyzed. A comparable experiment, the BaBar experiment , was in the USA. After the end of the data collection, the detector was converted to Belle II , which has been running since 2018.

The Belle Experiment published over four hundred scientific results, including

• the discovery of the CP violation , i.e. the violation of the symmetry between matter and antimatter , in the B-meson system. This observation has shown that CP violation manifests itself in nature in more than one particle physical system, namely at least in the K meson system and in the B meson system.
• the discovery of new penguin decays , in particular and . Penguin decays are a way of looking for new, previously unobserved particles that do not appear in the Standard Model .${\ displaystyle B \ to Kl ^ {+} l ^ {-}}$${\ displaystyle b \ to d \ gamma}$
• the discovery of several Tetraquark candidates, such as the X (3872) and the Z (4430). The latter carries an electrical charge and is therefore often regarded as the first hadron , which has been proven beyond doubt by an experiment , which has to be constructed with a minimum configuration of four quarks and therefore cannot represent either a meson or a baryon .

One of the 2008 Nobel Prize in Physics went to Makoto Kobayashi , the former director of the INPS (Institute of Particle and Nuclear Studies) department at KEK.The Belle experiment, which was instrumental in confirming the theoretical predictions, was specifically mentioned in the reason for the award contributed by Kobayashi and others .

1. K. Abe et al. a. (Belle Collaboration): Observation of Large Violation in the Neutral Meson System${\ displaystyle CP}$${\ displaystyle B}$ (Item No. 091802). In: Physical Review Letters . Vol. 87, No. 9, 2001 ( doi: 10.1103 / PhysRevLett.87.091802 ).
2. K. Abe et al. a. (Belle Collaboration): Observation of the Decay${\ displaystyle B \ to Kl ^ {+} l ^ {-}}$ (Item No. 021801). In: Physical Review Letters. Vol. 88, no., 2003 ( doi: 10.1103 / PhysRevLett.88.021801 ).
3. D. Mohapatra et al. a. (Belle Collaboration): Observation of and Determination of${\ displaystyle b \ to d \ gamma}$${\ displaystyle | V_ {td} / V_ {ts} |}$ (Item No. 221601). In: Physical Review Letters. Vol. 96, No. 22, 2006 ( doi: 10.1103 / PhysRevLett.96.221601 ).
4. S.-K. Choi et al. a. (Belle Collaboration): Observation of a Narrow Charmoniumlike State in Exclusive Decays${\ displaystyle B ^ {\ pm} \ to K ^ {\ pm} \ pi ^ {+} \ pi ^ {-} J / \ psi}$ (Item No. 262001). In: Physical Review Letters. Vol. 91, No. 26, 2003 ( doi: 10.1103 / PhysRevLett.91.262001 ).
5. S.-K. Choi et al. a. (Belle Collaboration): Observation of a Resonance Like Structure in the Mass Distribution in Exclusive Decays${\ displaystyle \ pi ^ {+ -} \ psi '}$${\ displaystyle B \ to \ pi ^ {+ -} \ psi '}$ (Article No. 142001). In: Physical Review Letters. Vol. 100, No. 14, 2008 ( doi: 10.1103 / PhysRevLett.100.142001 ).