Neutral strange particle production in\(\bar v\) Ne charged current interactions is studied using the bubble chamber BEBC, exposed to the CERN SPS antineutrino wide band beam. From a sample of 1191 neutral strange particles, the inclusive production rates are determined to be (15.7±0.8)% forK0 mesons, (8.2±0.5)% for Λ, (0.4±0.2)% for\(\bar \Lambda \) and (0.6±0.3)% for Σ0 hyperons. The inclusive production properties ofK0 mesons and Λ hyperons are investigated. The Λ hyperons are found to be polarized in the production plane.
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A study has been made of pseudoscalar mesons produced centrally in pp interactions. The results show that the eta and etaprime appear to have a similar production mechanism which differs from that of the pi0. The production properties of the eta and etaprime are not consistent with what is expected from double Pomeron exchange. In addition the production mechanism for the eta and etaprime is such that the production cross section are greatest when the azimuthal angle between the pT vectors of the two protons is 90 degrees.
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Resonance production as a function of dPT - the difference in the transverse momentum vectors of the two exchange particles, expressed as a percentage of its total contribution.
T distributions have been fitted to the form D(SIG)/D(T) = const(NAME=ALPHA)*EXP(-SLOPE(C=1)*T) + const(NAME=BETA)*T**2*EXP(-SLOPE(C=2)*T).
We present a systematic analysis of the production of K ∗+ (892) and Δ ++ (1236) resonances in the K + p → K 0 p π + reaction at 5, 8.25 and 16 GeV/ c . We have measured total cross sections, differential cross sections, density matrix elements and examined resonance production mechanisms in terms of the exchange of states with definite naturality. Some results on the reaction K + p → K ∗+ (1420) p are also given.
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Neutrino interactions in BEBC produce theDS** (2536) charmed strange meson. The mass of this state is 2534.2±1.2 MeV. The production rate is 0.011±0.005 per neutrino charged current interaction at a mean neutrino energy of 61 GeV. An earlier claim for another\(c\bar s\) bound state near 2565 MeV, produced in neutrino interactions, is not supported.
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The reactions K + p → K ∗+ (890) p , K + p → K ∗+ (1420) p and K + p → K 0 Δ ++ have been systematically studied for eleven incident momenta between 3.0 and 16.0 GeV/ c . Cross sections, differential cross sections and density matrix elements are presented. For K ∗ (890) production the contributions from natural and unnatural parity exchanges have also been separated into I = 0 and I = 1 components. Effective trajectories have been extracted in the case of natural parity exchange, and also for Δ ++ production.
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DATA AT NEIGHBOURING MOMENTA ARE GROUPED TOGETHER. THE RESONANCE PRODUCTION TOTAL CROSS SECTIONS ARE FITTED BY P**-N. THIS TABLE GIVES THE VALUES FOR EACH GROUP OF MOMENTA OF THE FITTED TOTAL CROSS SECTIONS WHICH ARE USED TO NORMALIZE THE DIFFERENTIAL CROSS SECTIONS.
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The production of the meson resonances ϱ(770) (all three charge states), η(550), ω(783) andf2(1270) in\(\bar v\) Ne and ν Ne charged current interactions is investigated in a bubble chamber experiment with BEBC at CERN. Except for thef2, the main features of resonance production are reasonably well described by the Lund model, although the average resonance multiplicities are overestimated by the model by (67±30)%. The average multiplicities of all resonances, including thef2, are well reproduced by a semiempirical model, whose parameters were determined from hadron interaction data.
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Enhanced production of strange baryons and anti-baryons at central rapidity in S-W and S-z.sbnd;S with respect to p-A reactions has been reported by the CERN experiments WA85 and WA94. The WA97 experiment is extending such a study to Pb Pb collisions making use of the newly developed silicon pixel detectors. Results on Λ, Ξ − and Ω − production in Pb Pb collisions at 158 A GeV/ c at central rapidity are presented. Transverse mass spectra and particle ratios are presented. Hyperon yields are given as a function of the collision centrality and compared with those obtained from p-Pb collisions using the same experimental setup.
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A study is presented of the reactions K + p→(K + ω )p at 8.25 and 16 GeV/ c and K − p→(K − ω )p at 10 and 16 GeV/ c and comparison is made with K + results at 10 GeV/ c and K − at 7.3 GeV/ c . The (K + ω) and (K − ω) mass spectra both present a strong enhancement very near threshold, while a second peak at ∼1.7 GeV is evident only with incident K − at the lower energies. The threshold peak has very weak energy dependence and is mostly due to the 1 + S state which is produced conserving s -channel helicity. It is suggested that this is another decay mode of the resonance Q 1 (1290) known to decay mainly into Kϱ. The ratio of the Q 1 coupling constants to the Kω and Kϱ decay channels, R ω = g K ω 2 / g K ϱ 2 is determined to be 0.21±0.04. The enhancement at 1.7 GeV is predominantly, but not exclusively, due to the 2 − state. While the K + and K − induced reactions give basically similar results, small differences are observed that can be qualitatively explained in the framework of the Deck model.
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Data from BEBC experiments are combined to provide large statistics for neutrino interactions. ChargedD* mesons are produced in (1.22±0.25)% of neutrino and (1.01±0.31)% of antineutrino charged current interactions. The mean fraction of the hadronic laboratory energy taken by theD*+ in these events is 0.59±0.03±0.08. Less than 18% of all chargedD* mesons from (anti)neutrino interactions are found to be daughters ofD**0 (at the 90% confidence level).
Mean fractional hadronic energy carried by the D*+- in the laboratory system.
Mean value of the Bjorken scaling variable X.
Rate of charged D* meson production per charged current neutrino interaction.
Results are presented on an analysis of the reaction K + p → K ∗+ (890) p at 16 GeV/ c and compared with data at lower incident momenta and with corresponding results for the reaction K − p → K ∗− (890) p. It is found for both reactions that the energy dependence of the cross section exhibits a simple ( p − n lab behaviour.
BREIT-WIGNER RESONANCE FITS WITH BACKGROUND.
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