In Belle's experiment, the researchers discovered for the first time the energy dependence of exclusive β-meson production reactions. The new data allow us to determine the nature of the exotic Upsilon meson group between 10.63 and 11.02 GeV. The results were published in the Journal of High Energy Physics. More than 400 researchers participated in Belle's experiment, including employees of the International Laboratory of Particle Physics of the Higher School of Economics.
The first Upsilon criterion, composed of b and anti-b quarks, was discovered in 1977. This event simultaneously became the discovery of the β-quark, for which American scientists Max Lederman, Melvin Schwartz and Jack Steinberger were awarded the Nobel Prize in 1988.
For the first time in 2008, scientists discovered that high-energy Upsilon mesons have anomalous properties. Knowing the reasons for these unexpected properties is one of the open questions in hadronic physics. According to theoretical studies, Upsilon states have additional degrees of freedom: light quark, antiquark or valence gluon. Such multiparticle bound states are called exotic hadrons, and they were unknown until recently. Further experimental data were needed to distinguish between the different models for the structure of the Upsilon criteria. Such data were collected in the Belle experiment in 2010 and formed the basis of a study published in the Journal of High Energy Physics.
The Belle detector operated from 1999 to 2010 at Japan's KEK-B electron-positron collider. Physicists around the world have studied the properties of the B+ and B0 criteria, which consist of a heavy anti-β quark and a single light u or d quark. Scientists have discovered the extremely rare decay of these particles, and also studied the differences in the properties of particles and antiparticles (B + and B-, B0 and anti-B0), which allowed us to get closer to understanding the mechanisms of their formation.
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