Discovery of new particle X(3872) - November 2003
The Belle collaboration at the KEK laboratory in Japan has discovered a new particle that does not fit to any known particle scheme. It is called the 'mystery meson'. It has a mass of 3.87 GeV and produced from the decay of B-mesons in electron-positron collisions at the KEK B-factory.
The new particle might contain four quarks (normal mesons contain two), similar to the Ds(2317).
This suggests a possibility of an entirely new mesonic class of particle.
Neutrino oscillation - November 2004
The KamLand (Kamioka Liquid scintillator Anti-Neutrino Detector) experiment in Japan have provided the most convincing proof that neutrinos have mass and can oscillate between different flavors. This findings were derived from measurements of the
energy spectrum of electron anti-neutinos from fission reactions produced by the surrounding 53 nuclear power stations.
Neutrinos are assumed to have no mass in the Standard Model but now this needs to be revised. The team studied the oscillation behavior by plotting the number of detected antineutrinos as a function of L/E where L is the distance travelled by the antineutino (from a nuclear reactor to the detector) and E is the energy measured
in the detector. The results show the antineutrinos dissappear and then reappear again. The findings confirm earlier work at the Sudbury Neutrino Observatory in Canada and Super-Kamiokande in Japan.
Bottom to down quark decay - July 2005
The Belle collaboration at the KEK laboratory in Japan has confirmed the first sighting of a very rare process whereby a bottom quark decays into a down quark. This process involves the decay of heavy third generation quark (bottom) into
first, lighter generation of quark (down), a process that is suppressed by the generation structure of the Standard Model. The process was observed in the KEK beam collisions of electron and positron to produce pairs of B-meson, each of which contains a bottom quark and an antiquark.
Out of a sample of 390 million such events, 35 events were registered whereby a B-meson decays into either a r or an w meson, which contain up and down quarks, and 30 events where B-meson disintegrate into two K-mesons, one of which contained a down quark.
This is predicted in Standard Model, but other theories beyond the Standard Model such as supersymmetry (SUSY) also predict such process. SUSY predicts that every fundamental particle has a massive 'super' partner. The observation therefore allows scientists to predict physics beyond the Standard Model.
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