Search for Theta(1540)^+ in exclusive proton-induced reaction p+C(N) \to Theta^+ \bar{K}^0 + C(N) at the energy of 70 GeV

SPHINX Collaboration; Antipov, Yu. M.; Artamonov, A. V.; Batarin, V. A.; Eroshin, O. V.; Kolganov, V. Z.; Konstantinov, A. S.; Kozhevnikov, A. P.; Kurshetsov, V. F.; Kushnirenko, A. E.; Landsberg, L. G.; Leontiev, V. M.; Lomkatsi, G. S.; Mukhin, V. A.; Molchanov, V. V.; Nilov, A. P.; Patalakha, D. I.; Petrenko, S. V.; Petrukhin, A. I.; Smolyankin, V. T.; Vavilov, D. V.; Victorov, V. A.

Search for Theta(1540)^+ in exclusive proton-induced reaction p+C(N) \to Theta^+ \bar{K}^0 + C(N) at the energy of 70 GeV

Authors

Description

A search for narrow Theta(1540)^+, a candidate for pentaquark baryon with positive strangeness, has been performed in an exclusive proton-induced reaction p+C(N) \to Theta^+ \bar{K}^0 + C(N) on carbon nuclei or quasifree nucleons at E_{beam}=70 GeV (sqrt{s} = 11.5 GeV) studying nK^+, pK_S and pK_L decay channels of Theta(1540)^+ in four different final states of the Theta^+ \bar{K}^0 system. In order to assess the quality of the identification of the final states with neutron or K_L we reconstructed Lambda(1520)\to nK_S and phi\to K_LK_S decays in the calibration reactions p+C(N)\to Lambda(1520)K^+ + C(N) and p+C(N)\to pϕ+ C(N). We found no evidence for narrow pentaquark peak in any of the studied final states and decay channels. Assuming that the production characteristics of the Theta^+ \bar{K^0} system are not drastically different from those of the Lambda(1520)K^+ and pϕsystems, we established upper limits on the cross section ratios sigma(Theta^+\bar{K}^0)/sigma(Lambda(1520)K^+) < 0.02 and sigma(Theta^+\bar{K}^0)/sigma(pϕ) < 0.15 at 90% CL and a preliminary upper limit for the forward hemisphere cross section sigma(Theta^+\bar{K}^0) < 30 nb/nucleon.
14 pages; 16 figures. Based on talks given by V.F.Kurshetsov at the IHEP seminar (Protvino, IHEP, February 5, 2004) and at the session of Nuclear Department of Russian Academy of Science (Moscow, ITEP, March 5, 2004)