Production of multi-strange baryons and antibaryons is expected to be a useful indicator in the search for Quark-Gluon Plasma formation. Production of Ξ − and Ξ − has been observed for the first time in ultra-relativistic heavy ion interactions by the WA85 Experiment. We describe the procedure used to select these cascade candidates and show that Ξ − and Ξ − decays can be identified. Preliminary ratios of Ξ/Ξ production in sulphur-tungsten and proton-tungsten interactions are also presented.
PRODUCTION AT CENTRAL RAPIDITY. 123 XI- AND 53 XIBAR+ CANDIDATES.
PRODUCTION AT CENTRAL RAPIDITY. 82 XI- AND 22 XIBAR+ CANDIDATES.
Inclusive K ∗0 production is studied in π − p interactions at 16 GeV/ c with x ϝ > 0.2. The K ∗0 is found to be pre-dominantly centrally produced with cross section σ( K ∗0 ) = (72 ± 12) μb for x ϝ > 0.2 and compares closely to data on K ∗0 production in π + p interactions at the same energy.
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Experimental results on the reaction π − p → K ∗0 (890) X 0 at 10 GeV /c are presented. By using the K ∗0 polarization measurements, a detailed study of the production has been carried out as a function of the missing mass squared and of the four-momentum trasnfer squared to the K ∗0 . We found that: (a) K ∗0 production is dominated by natural parity exchange; (b) K ∗0 helicity-zero production dominates the unnatural parity exchange contribution and (c) the main features of the reaction are in agreement with the predictions of the finite mass sum rules.
TO TAL (NATURAL+UNATURAL PARITY EXCHANGE) CROSS-SECTIONS.
NATURAL PARITY EXCHANGE CROSS-SECTIONS.
UNATURAL PARITY EXCHANGE CROSS-SECTIONS.
Inclusive φ production is studied in π − p collisions at 16 GeV/ c . The φ cross section for Feynman variable x φ > 0.2 is found to be (15.5 ± 3.6) μb. This leads to an extrapolated cross section of (29.9 ± 7.0) μb for x φ > 0.0. Fitting the momentum transfer squared distribution of the φ to the form e −bp 2 T gives an average slope of b = (2.4 ± 0.3) (GeV/ c −2 for x φ > 0.5.
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Production of Ξ − and Ξ − has been observed for the first time in heavy ion interactions by the WA85 Experiment. Multistrange baryon and antibaryon production is expected to be a useful probe in the search for quark-gluon plasma formation. We describe the procedure used to select these cascade candidates and show that Ξ − and Ξ − decays can be identified. The ratio of Ξ Ξ production, corrected for geometrical acceptances and reconstruction efficiencies, is 0.39 ± 0.07 for sulphur-tungsten interactions in the central rapidity interval 2.3< Y lab <3.0 and p T >1.1 GeV/ c .
The transverse momentum distributions for\(\rho ^0 (770),f_2 (1270),K*^0 (892),\bar K*^0 (892)\) and ϕ (1020) have been studied in thept region between 2 and 4 GeV/c and central rapidity. The data analysed come from the WA77 experiment at CERN with a 300 GeV/c π− beam incident on a Be target. These distributions are well described by the functionpt−n withn∼8. A sample of simulated events from the Lund Monte Carlo in the same experimental conditions reproduces well the data.
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Acceptance corrected tranverse momentum distribution.
Acceptance corrected tranverse momentum distribution.
Strange and multistrange baryon production is expected to be enhanced in heavy ion interactions if a phase transition from hadronic matter to a Quark-Gluon Plasma takes place. The production yields of Λ s, Λ s, Ξ − s, and Ξ + s relative to the production of negative particles are presented for sulphur-tungsten interactions at 200 GeV/ c per nucleon. These production yields are compared to those produced in proton-tungsten interactions and the enhancements of strange and multistrange baryons and antibaryons are presented.
Hyperon to negative production ratios with sulphur beam.
Hyperon to negative production ratios with proton beam.
Strange and multistrange baryon enhancements.
Strange and multistrange baryon and antibaryon production has been studied in sulphur sulphur interactions at 200 GeV/ c per nucleon at central rapidity using the CERN Omega Spectrometer. Particle production ratios and transverse mass spectra are presented for Λ, Ξ − , Λ and Ξ − .
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Strange and multistrange baryon and antibaryon production is a useful probe into the dynamics of the hot hadronic matter created in central heavy ion interactions. Relative production yields and transverse mass spectra are presented for Λ, Λ , Ξ − and Ξ + hyperons produced in central sulphur-tungsten interactions at 200 GeV/ c per nucleon.
Distributions are fitted with (1/MT**1.5)*DN/DMT=CONST*EXP(-MT/SLOPE).
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