Evidence for Pentaquark states Nakano, Nuclear Physics A738 2004: 182 Stephen Pittman, 121306

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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, ?, with
  a mass of 1540 MeV and a narrow width.
• This particle has Strangeness 1 and quark
  configuration uudds
• First proposed by Diakonov, Petrov, Polyakov
  (1997)

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• A laser-electron photon (LEP) beam (2.4 GeV max)
  shot at liquid hydrogen target
• ? n ? K- ? ? K- K n
• 19 estimated events above background levels with
  Gaussian significance of 4.6s

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• DIANA at ITEP (Russia) reexamined low-energy K
  Xe collisions from 1986
• They discovered a 1539 MeV peak with lt 9 MeV
  width (4.4s) in pK0 mass spectrum (KXe? K0 pXe)
• CLAS at Jefferson Lab reanalyzed data from 1999
  and found peak at 1542 MeV in n K mass spectrum
  (?d? K K- pn)
• SAPHIR at ELSA (Germany) reanalyzed old data and
  found peak at 1540 MeV with width lt 25 MeV (?p?
  K0 Kn)