Search for the Θ+ pentaquark in the reactions γp→K̄ 0K+n and γp→K̄0K0p

R. De Vita, M. Battaglieri, V. Kubarovsky, N. A. Baltzell, M. Bellis, J. Goett, L. Guo, G. S. Mutchler, P. Stoler, M. Ungaro, D. P. Weygand, M. J. Amaryan, P. Ambrozewicz, M. Anghinolfi, G. Asryan, H. Avakian, H. Bagdasaryan, N. Baillie, J. P. Ball, V. BatourineI. Bedlinskiy, N. Benmouna, B. L. Berman, A. S. Biselli, S. Boiarinov, S. Bouchigny, R. Bradford, D. Branford, W. J. Briscoe, W. K. Brooks, S. Bültmann, V. D. Burkert, C. Butuceanu, J. R. Calarco, S. L. Careccia, D. S. Carman, S. Chen, E. Clinton, P. L. Cole, P. Collins, P. Coltharp, D. Crabb, H. Crannell, V. Crede, J. P. Cummings, D. Dale, R. De Masi, E. De Sanctis, P. V. Degtyarenko, A. Deur

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The exclusive reactions γp→K̄0K+n and γp→K̄ 0K0p have been studied in the photon energy range 1.6-3.8 GeV, searching for evidence of the exotic baryon Θ+(1540) in the decays Θ+→nK+ and Θ+→pK0. Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. The integrated luminosity was about 70pb-1. The reactions have been isolated by detecting the K+ and proton directly, the neutral kaon via its decay to KS→π+π- and the neutron or neutral kaon via the missing mass technique. The mass and width of known hyperons such as Σ+, Σ- and Λ(1116) were used as a check of the mass determination accuracy and experimental resolution. Approximately 100000 Λ*(1520)'s and 150000 's were observed in the K̄0K+n and K̄0K0p final state, respectively. No evidence for the Θ+ pentaquark was found in the nK+ or pKS invariant mass spectra. Upper limits were set on the production cross section of the reaction γp→K̄ 0Θ+ as functions of center-of-mass angle, nK+ and pKS masses. Combining the results of the two reactions, the 95% C.L. upper limit on the total cross section for a resonance peaked at 1540 MeV was found to be 0.7 nb. Within most of the available theoretical models, this corresponds to an upper limit on the Θ+ width, ΓΘ+, ranging between 0.01 and 7 MeV.

Original languageEnglish (US)
Article number032001
JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
Issue number3
StatePublished - 2006


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