Diffractive excitation of proton into strange particles at very high energies

Experimental results on the study of single diffraction dissociation (SDD) of proton into strange particles in proton-proton interaction at c.m. energies, √s = 45 and 53 GeV, are presented. The following reactions were studied: pp → (Λ0K+)p, pp → (p phi)p, and pp → (Λ(1520)K+)p. Results on the latter two reactions come from the exclusive reaction: pp → (pK+K-)p. The principle features of the data are: The effective mass distribution of Λ0K+ peaks around 1.7 GeV in the reaction pp → Λ0K+p. The corresponding cross section is 9.0 +- 2.7 ub for M(Λ0K+) < 2.5 GeV. The t dependence is well fitted by an exponential form Ae/sup bt/ with b = 7.0 +- 0.5 GeV-2. Assuming the peak of Λ0K+ invariant mass at 1.7 GeV is due to N(1688), the branching fraction GAMMA/sub AK//GAMMA for the decay of N(1688) is 1.0 +- 0.3%. (2) There is no evidence for the Zweig's rule suppressed reaction pp → (p phi)p. The upper limit of production cross section is found to be 0.3 ub at 95% significance level for M(p phi) < 2.8 GeV. (3) The reaction pp → pK+K-p is dominated by Λ(1520) production. The cross section for pp → Λ(1520)K+p is 2.7 +- 0.8 ub for M(Λ(1520)K+) < 2.6 GeV. This is the first high statistics study of the reaction pp → N*p, with N* decaying into strange particles, which is part of a program studying the single diffraction dissociation of proton at very high energies. The data yields the first unambiguous observation of N(1688) → Λ0K+ and the first observation of the proton excitation to Λ(1520)K+. The apparent nonobservation of phi-meson production in the reaction pp → p phi p at ISR energies is consistent with Zweig's rule