Observation of an Exotic Baryon with S=+1 in Photoproduction from the Proton
The reaction {gamma}p {yields} {pi}{sup +} K{sup -} K{sup +}n was studied at Jefferson Lab using a tagged photon beam with an energy range of 3-5.47 GeV. A narrow baryon state with strangeness S = +1 and mass M = 1555 {+-} 10 MeV/c{sup 2} was observed in the nK{sup +} invariant mass spectrum. The peak's width is consistent with the CLAS resolution (FWHM = 26 MeV/c{sup 2}), and its statistical significance is 7.8 {+-} 1.0 {sigma}. A baryon with positive strangeness has exotic structure and cannot be described in the framework of the naive constituent quark model. The mass of the observed state is consistent with the mass predicted by a chiral soliton model for the {Theta}{sup +} baryon. In addition, the pK{sup +} invariant mass distribution was analyzed in the reaction {gamma} p {yields} K{sup -} K{sup +}p with high statistics in search of doubly-charged exotic baryon states. No resonance structures were found in this spectrum.
- Research Organization:
- Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
- Sponsoring Organization:
- USDOE; USDOE Office of Energy Research (ER) (US)
- DOE Contract Number:
- AC05-84ER40150
- OSTI ID:
- 836840
- Report Number(s):
- JLAB-PHY-03-203; DOE/ER/40150-3139; hep-ex/0311046; PRLTAO; TRN: US0500811
- Journal Information:
- Physical Review Letters, Vol. 92; Other Information: PBD: 1 Jan 2004; ISSN 0031-9007
- Country of Publication:
- United States
- Language:
- English
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