The production of neutral strange particlesKso, Λ and\(\bar \Lambda \) has been studied in 60 and 200 GeV per nucleon OAu and pAu collisions with the streamer chamber vertex spectrometer of the NA35 experiment at the CERN-SPS accelerator. Ratios of neutral strange particle production to negatively charged particle production in selected regions of phase space were measured to be the same in OAu and pAu reactions. The rates of strange particle production in central OAu collisions are about a factor of 16 higher than in pAu collisions when compared in the same regions of phase space. If an enhancement of strange particle production in OAu collisions relative to pAu collisions is considered to be a signature for quark-gluon plasma formation, no evidence supporting it is observed. The experimental results are compared to the Lund FRITIOF model.
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A study of the polarization of $\Lambda$ hyperons produced in inelastic pN reactions induced by the 450 GeV proton beam from the CERN SPS has been performed with t
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Λ , Ξ and Ω yields and transverse mass spectra have been measured in Pb-Pb and p-Pb collisions at 158 A GeV/ c . The yields in Pb-Pb interactions are presented as a function of the collision centrality and compared with those obtained from p-Pb collisions. Strangeness enhancement is observed which increases with centrality and with the strangeness content of the hyperon.
Measured slope for P-PB with POWER=3/2.
Measured slope for PB-PB with POWER=3/2.
Measured slope for P-PB with POWER=1.0.
The WA94 experiment uses the production of strange particles and antiparticles to investigate the properties of hot hadronic matter created in heavy-ion interactions. Λ, Λ , Ξ − and Ξ + particle yields and transverse mass spectra are presented for pS interactions. These results are compared with those from SS interactions. Our results are also compared with those from pW and SW interactions of the WA85 experiment.
The fit with formula (1/MT**1.5)*D(SIG)/D(MT) = CONST*EXP(MT/SLOPE).
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Inclusive differential cross sections $d\sigma_{pA}/dx_F$ and $d\sigma_{pA}/dp_t^2$ for the production of \kzeros, \lambdazero, and \antilambda particles are measured at HERA in proton-induced reactions on C, Al, Ti, and W targets. The incident beam energy is 920 GeV, corresponding to $\sqrt {s} = 41.6$ GeV in the proton-nucleon system. The ratios of differential cross sections \rklpa and \rllpa are measured to be $6.2\pm 0.5$ and $0.66\pm 0.07$, respectively, for \xf $\approx-0.06$. No significant dependence upon the target material is observed. Within errors, the slopes of the transverse momentum distributions $d\sigma_{pA}/dp_t^2$ also show no significant dependence upon the target material. The dependence of the extrapolated total cross sections $\sigma_{pA}$ on the atomic mass $A$ of the target material is discussed, and the deduced cross sections per nucleon $\sigma_{pN}$ are compared with results obtained at other energies.
Inclusive differential cross section DSIG/DXL for K0S production in the XL interval -0.12 to 0.0 plus the total cross section after extrapolation to the full XL range.
Inclusive differential cross section DSIG/DXL for LAMBDA production in the XL interval -0.12 to 0.0 plus the total cross section after extrapolation to thefull XL range.
Inclusive differential cross section DSIG/DXL for LAMBDABAR production in the XL interval -0.12 to 0.0 plus the total cross section after extrapolation to the full XL range.
The ratio of the cross section for Σ0 inclusive production to the cross section for Λ0 inclusive production has been measured with 28.5-GeV/c protons incident on a beryllium target at an average laboratory production angle of 4°. This ratio was measured to be 0.278±0.011±0.05, where the uncertainties are statistical and systematic in that order. The ratio does not depend strongly on the momentum of the produced particle between 10 and 24 GeV/c. The effect of Σ0 contamination on previous determinations of the polarization of inclusively produced Λ0’s is discussed.
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We have used the Fermilab 30-in. bubble-chamber-hybrid spectrometer to study neutral-strange-particle production in the interactions of 200-GeV/c protons and π+ and K+ mesons with nuclei of gold, silver, and magnesium. Average multiplicities and inclusive cross sections for K0 and Λ are measured, and a power law is found to give a good description of their A dependence. The exponent characterizing the A dependence is consistent with being the same for K0 and Λ production, and also the same for proton and π+ beams. Average K0 and Λ multiplicities, as well as their ratio, have been measured as functions of the numbers of projectile collisions νp and secondary collisions νs in the nucleus, and indicate that rescattering contributes significantly to enhancement of Λ production but not to K0 production. The properties of events with multiple K0's or Λ's also corroborate this conclusion. K0 rapidities are in the central region and decrease gently with increasing νp, while Λ rapidities are in the target-fragmentation region and are independent of νp. K0 and Λ multiplicities increase with the rapidity loss of the projectile, but their rapidities do not.
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Data on multiplicity, correlations, and inclusive spectra of KS0 mesons and Λ0(Λ¯0) hyperons produced with xF≤0 in inelastic pNe20 and pN interactions at 300 GeV are presented and compared. The inclusive cross sections for pNe20 (pN) with xF≤0 are 61.1±2.8 mb (3.34±0.64 mb) for KS0, 40.8±2.5 mb (1.89±0.29 mb) for Λ0, and 3.9±0.5 mb (0.31±0.08 mb) for Λ¯0. The multiplicity ratio for pNe20 and pN interactions is 1.58±0.16 for KS0, 1.95±0.23 for Λ0, and 1.12±0.43 for Λ¯0. We have observed the Σ0(1193) hyperon and measured the average multiplicity (nΣ0=0.049±0.027) for xF≤0. We have also observed the strange resonances K*(892), K*(1415), and Σ*(1385) with xF≤0 and measured the fraction of V0 coming from each resonance. Λ0 polarization for xF≤0 is measured and shows a decrease as p⊥ increases [pΛ(pNe20)≈−0.25 at p⊥=1.5 GeV/c], in agreement with other experiments which measure polarization in the region xF≫0. Since (43±7)% of the Λ0 are produced in Σ0→Λ0γ decays, the Λ0 polarization is significantly greater than the measured values. Experimental results are compared to predictions of the Lund model and the dual parton model of soft hadron-nucleus and hadron-nucleon interactions.
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Axis error includes +- 0.0/0.0 contribution (NOT GIVEN).
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The production of Λ,\(\bar \Lambda\) andKs0 has been studied in 200 GeV/nucleonp+S and S+S collisions in the streamer chamber of the NA35 experiment at the CERN SPS. Significant enhancement of the multiplicities of all observed strange particles relative to negative hadrons was observed in central S+S collisions, as compared top+p andp+S collisions. The latter collisions show no overall (relative) strangeness enhancement overp+p, but the rapidity distributions and hadron multiplicities indicate some secondary cascading production of Λ particles in thep+S andp+Au collisions. The Λ polarization in central S+S collisions was found to be compatible with zero up topT=2 GeV/c.
Tranverse kinetic energy spectra of neutral strange particles in P SU collisions.
Tranverse kinetic energy spectra of neutral strange particles in P SU collisions.
Tranverse kinetic energy spectra of neutral strange particles in SU SU collisions.
The authors have measured the polarization of 2.4×105 Λ0 hyperons in inclusive production by 12-GeV protons on tungsten at three production angles, 3.5°, 6.5°, and 9.5°. In terms of Feynman's xF and transverse momentum of Λ0, the kinematical range is 0.3<~xF<~0.8 and 0.4<~pT<~1.6 GeV/c. The observed polarization does not depend strongly on xF and increases linearly with pT to 16% at pT=1.0 GeV/c, showing a tendency to level off above that point.
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