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Z(4430)*2
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Physicists at the Belle experiment at the KEK laboratory in Japan have discovered a new particle that provides the best evidence yet that some mesons could contain four quarks, not two.
The rogue particle is an unusual charged meson. Mesons such as pions and kaons consist of a quark and an antiquark pair, while baryons such as protons and neutrons are made up of three quarks or three antiquarks.
Four-quark state under the guise of ordinary mesons are possible in quantum chromodynamics (QCD), but until recently no compelling evidence for such particles had emerged.
Two years ago the BaBar experiment at the Stanford Linear Accelerator Centre in the US reported an unusually long-lived excited meson called the DsJ(2317), that had a mass of 2317 MeV.

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An international team of researchers at the High Energy Accelerator Research Organization (KEK) in Tsukuba, Japan, the "Belle collaboration"*1, recently announced the discovery of an exotic new sub-atomic particle with non-zero electric charge. This particle, which the researchers have named the Z(4430)*2, does not fit into the usual scheme of "mesons", combinations of a quark*3and an antiquark that are held together by the force of the strong interaction.
The Z(4430) particle was found in the decay products of B-mesons (mesons containing a "bottom" quark) that are produced in large numbers at the KEKB "B-factory", an electron-positron collider at the KEK laboratory. While investigating various decays of the B meson in a data sample containing about 660 million pairs of B and anti-B mesons, the Belle team observed 120 B mesons that decay into a Z(4430) and a K-meson. The Z(4430) then instantly decays into a "Psi-prime" (Psi-prime) particle and a pi-meson. The Belle team found that this particle has the same electric charge as the electron and a mass about 4.7 times that of the proton.

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RE: D-meson mixing
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For the first time, scientists of the BaBar experiment at the Department of Energy's Stanford Linear Accelerator Centre (SLAC) have observed the transition of one type of particle, the neutral D-meson, into its antimatter particle. This observation will now be used as a test of the Standard Model, the current theory that best describes all the universe's luminous matter and its associated forces.

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Whilst science fiction toys effortlessly with anti-matter, in reality it can be very hard to produce, so researchers around the world are celebrating a new break through in this area. For the first time, scientists using the BaBar experiment at the Stanford Linear Accelerator Center (SLAC) have observed the transition of one type of particle, the neutral D-meson, into its antimatter particle - a process known as 'mixing'. The new observation will be used as a test of the Standard Model, the current theory that best describes the entire universe's luminous matter and its associated forces.

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