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A laser-electron photon (LEP) beam (2.4 GeV max) shot at liquid hydrogen target

Evidence for Penta-quark states Nakano, Nuclear Physics A738 (2004): 182 Stephen Pittman, 12/13/06. The LEPS collaboration at SP ring-8 is the first to claim the existence of a pentaquark, θ + , with a mass of 1540 MeV and a narrow width.

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A laser-electron photon (LEP) beam (2.4 GeV max) shot at liquid hydrogen target

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  1. Evidence for Penta-quark states Nakano, Nuclear Physics A738 (2004): 182Stephen Pittman, 12/13/06 • The LEPS collaboration at SP ring-8 is the first to claim the existence of a pentaquark, θ+, with a mass of 1540 MeV and a narrow width. • This particle has Strangeness = 1 and quark configuration uuddŝ • First proposed by Diakonov, Petrov, Polyakov (1997)

  2. A laser-electron photon (LEP) beam (2.4 GeV max) shot at liquid hydrogen target γ + n  K- + θ+ K- + K+ + n • 19 estimated events above background levels with Gaussian significance of 4.6σ

  3. DIANA at ITEP (Russia) reexamined low-energy K+ Xe collisions from 1986 • They discovered a 1539 MeV peak with < 9 MeV width (4.4σ) in pK0 mass spectrum (K+Xe K0 pXe) • CLAS at Jefferson Lab reanalyzed data from 1999 and found peak at 1542 MeV in n K+ mass spectrum (γd K+ K- pn) • SAPHIR at ELSA (Germany) reanalyzed old data and found peak at 1540 MeV with width < 25 MeV (γp K0 K+n)

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