Measurements of inclusive production of the Lambda, Xi- and Xi*(1530) baryons in two-photon collisions with the L3 detector at LEP are presented. The inclusive differential cross sections for Lambda and Xi- are measured as a function of the baryon transverse momentum, pt, and pseudo-rapidity, eta. The mean number of Lambda, Xi- and Xi*(1530) baryons per hadronic two-photon event is determined in the kinematic range 0.4 GeV < pt< 2.5 GeV, |eta| < 1.2. Overall agreement with the theoretical models and Monte Carlo predictions is observed. A search for inclusive production of the pentaquark theta+(1540) in two-photon collisions through the decay theta+ -> proton K0s is also presented. No evidence for production of this state is found.
Differential cross section for LAMBDA production.
Differential cross section for LAMBDA production.
Differential cross section for XI- production.
The production of Λ hyperons in e+e− annihilation has been measured as a function of their total momenta, transverse momenta, and the event thrust. The total production rate is 0.213±0.012±0.018 Λ or Λ¯ per hadronic event. The observation of correlations in rapidity and angles for events with two detected Λ decays supports fragmentation models with local baryon-number compensation.
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The inclusive production cross sections and transverse momentum distributions of K*0 and KS0 mesons in e+e− annihilation at a center-of-mass energy of 29 GeV have been measured by means of the time projection chamber detector in the PEP-4 experiment. The mean multiplicites are found to be 0.49 ± 0.04(stat.) ± 0.07(syst.) (K*0+K―*0) and 1.22 ± 0.03(stat.) ±0.15(syst.) (K0+K―0) per event.
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The inclusive production ofK*±(890), ρρ(770), ω0(780) andf0(1,270) mesons is studied in\(\bar pp\) experiment at 32GeV/c in the MIRABELLE bubble chamber by the analysis of (K0π±) and (π+π−) invariant mass distributions. The inclusive cross sections are σ(K*±)=2.45±0.30 mb, σ(ρ0)=8.8 ±0.9 mb, σ(ω+)≃6.2 mb, and σ(f0)=2.2±0.7 mb. The C.M. longitudinal distribution of theK*±(890) is slightly shifted to the primary particles fragmentation regions; the ρ0 is produced more centrally. The studied mesons alone are responsible for 40% of final state poins. The production features of various resonances are compared with quark models predictions.
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The reactions p p → K ∗ (890) X , p p →Σ ± (1385) X and p p → S ∗ (993) X at 12 GeV/ c incident momentum have been studied using 19 000 events with a visible V 0 decay in BEBC. Inclusive production cross sections of these resonances as a function of transverse momentum and rapidity are presented. The contribution of annihilation to the production of the K ∗ (890) is investigated from a comparison with the corresponding pp data.
COMBINDED K*+ AND K*- DATA IN THIS TABLE.
COMBINDED K*+ AND K*- DATA IN THIS TABLE.
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The inclusive production of K̄ ∗ (890) and K̄ ∗ (1420) is studied in K̄ − p interactions at 10 and 16 GeV/ c . At 10 GeV/ c an enhancement in the ( K ̄ 0 π − ) mass distribution is found at 1.74 GeV, but no clear signal is seen at 16 GeV/ c . The fraction of K 0 ' s coming from decay of the K ∗ (890) or K ∗ (1420) is large, being (50 ± 6)% and (45 ± 5)% at 10 and 16 GeV/ c , respectively. The inclusive cross sections for K ∗− (890) and K ∗0 (890) production are almost constant with energy from 8 to 32 GeV/ c with values of 3.5 and 3.3 mb, respectively. The K ∗ (890) production cross section is studied as a function of transverse and longitudinal variables and found to derive mainly from fragmentation of the incident K − meson. The spectra of K 0 ' s resulting from the decay of K ∗ (890) are studied.
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Inclusive production of Λ and Λ in K + p interactions is studied at incident momenta of 8.2 and 16.0 GeV/ c . Cross sections and single-particle distributions are presented, the correlation between longitudinal and transverse momentum is investigated, and the dependence of average charge multiplicity on missing mass measured. For Λ production, early scaling is observed in the target fragmentation region when the data are presented in terms of ( M 2 - M th 2 )/ s and t , where M th is the threshold value of the missing mass M . Furthermore, a triple-Regge analysis in these variable yields an effective exchange trajectory which passes through the K, Q and L mesons. There is evidence for beam fragmentation in Λ and Λ production, but the contributions seem not to be dominant in the fragmentation region. Nevertheless, the parameter values in a triple-Regge description are estimated, and together with those for target fragmentation in Λ production, provide a complete description of the fragmentation contributions to the two reactions. Integration of the resultant distribution functions over the complete Chew-Low plot yields fragmentation cross sections increasing approximately as log s ; in addition the observed features of the x , p L and p T 2 projections and of the p L - p T correlation are well-described in the fragmentation regions. Central production contributions are isolated by subtracting the calculated fragmentation distributions
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Results are presented on the inclusive reactions p p → K 0 X , p p → Λ X and p p → Λ X at an incident antiproton momentum of 12 GeV/ c in BEBC. The cross sections are studied as functions of the Feynman scaling variable x , the rapidity, the transverse momentum of the V 0 and the missing mass squared. The dependence of the Λ and Λ polarization on x are also studied. Comparisons with proton-proton data at 12 GeV/ c are also made. Finally, events with two detected V 0 are analyzed in order to study correlations arising from the production of two strange neutral particles.
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Total and semi-inclusive cross sections, longitudinal and transverse momentum distributions and spin density matrix elements of theK*+(892) andK*0(892) produced in the inclusive reactionsK+p→K*+(892)+X andK+p→K*0(892)+X at 32 GeV/c are studied in detail. The inclusive spectra of theK*(892) and their decay products are compared with pion and neutral kaon production. TheK*+(892) andK*+(892) are dominantly produced by kaon fragmentation processes. The dependence of average transverse momentum <pT> vs.x for resonances has been investigated for the first time.
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