Phantasmagorical Pentaquarks

Credit: LHCb

The LHCb collaboration submitted today a paper based on run 1 data which reports the observation of pentaquark-charmonium states decaying into a J/ψ meson and a proton p. In the traditional quark model, the strongly interacting particles (hadrons) are formed either from quark-antiquark pairs (mesons) or three quarks (baryons). Particles which cannot be classified within this scheme are called exotic hadrons. In his fundamental 1964 paper, in which he proposed the quark model, Gell-Mann mentioned the possibility of adding a quark-antiquark pair to a minimal meson or baryon quark configuration. It has taken 50 years, however, for measurements to be performed that unambiguously demonstrate the existence of these exotics. In April 2014 the LHCb collaboration published results of measurements which demonstrated that the Z(4430)+ particle, first observed by the Belle collaboration, is composed of four quarks (ccdu). Today, the collaboration has announced the observation of a pentaquark, that is a hadron consisting of five quarks. … (CERN/LHC)

Credit: LHCb

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