Search for Theta++ pentaquarks in the exclusive reaction gammap-->K+K-p.
The reaction gammap --> pK+K- was studied at Jefferson Lab with photon energies from 1.8 to 3.8 GeV using a tagged photon beam. The goal was to search for a Theta++ pentaquark, a narrow, doubly charged baryon state having strangeness S=+1 and isospin I=1, in the pK+ invariant mass spectrum. No statistically significant evidence of a Theta++ was found. Upper limits on the total and differential cross section for the reaction gammap --> K-Theta++ were obtained in the mass range from 1.5 to 2.0 GeV/c2, with an upper limit for a narrow resonance with a mass M(Theta++) = 1.54 GeV/c2 of about 0.15 nb, 95% C.L.. This result places a stringent upper limit on the Theta++ width Gamma(Theta++) <0.1 MeV/c2.
Kubarovsky
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Rensselaer Polytechnic Institute, Troy, New York 12180-3590, USA.
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Goett
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Mutchler
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Bradford
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Briscoe
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Brooks
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Bültmann
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Burkert
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Butuceanu
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Calarco
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Careccia
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Carman
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Chen
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Clinton
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Cole
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Crannell
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Crede
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Cummings
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Egiyan
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Egiyan
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Hersman
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Kim
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Niyazov
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Ostrovidov
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