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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We have studied ϱ − production at 8 GeV / c . The data cannot be explained by one-pion-exchange with absorption and we conclude that vector exchange contributes. This contrasts with ϱ o production at this energy and ϱ − production at lower energy.
The diffractive production of ρ0(770 @#@) mesons in muon-proton interactions is studied in the kinematic region 0.15 GeV2< Q2< 20 GeV2 and 20 GeV < ? < 420 GeV. The data were obtained in the Fermilab fixed-target experiment E665 with primary muons of 470 GeV energy. Results are presented on the Q2, x and ? dependence of the cross section, on the shape of the ρ+ρt - mass spectrum, on the slope of the diffraction peak and on the production and decay angular distributions of the ρ0(770). The cross section for diffractive production of ρ0 by virtual photons on protons depends mainly on Q2. At fixed Q2, no significant dependence on x or ? is observed. The extrapolation to Q2 = 0 yields a photoproduction cross section of (10.30 ± 0.33) μb. The slope of the t′ distribution has a value of (7.0 ± 0.2) GeV−2, with a tendency to decrease as Q2 increases. The production and decay angular distributions of the ρ0 depend strongly on Q2 and are consistent with s-channel helicity conservation. The ratio R = σl/σt deduced from the decay angular distributions rises strongly with Q2, passing the value of 1 at Q2≈ 2 GeV2.
Statistical errors only.
Statistical errors only.
Cross section extrapolated to Q**2 = 0.
Antiproton production near midrapidity has been studied in central collisions of 32 S with sulphur, silver and gold nuclei at 200 GeV per nucleon. The measured transverse mass distributions can be described by an exponential with inverse slope parameters of about 200 MeV, similar to those obtained from Λ spectra. The rapidity density increases weakly with the target mass, ranging from 0.4 to 0.7. The ratio Λ p near midrapidity is approximately 1.4 on average, significantly larger than the corresponding ratio observed in proton-proton and proton-nucleus collisions.
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The production ofK0, Λ and\(\bar \Lambda \) particles is studied in the E665 muon-nucleon experiment at Fermilab. The average multiplicities and squared transverse momenta are measured as a function ofxF andW2. Most features of the data can be well described by the Lund model. Within this model, the data on the K0/π± ratios and on the averageK0 multiplicity in the forward region favor a strangeness suppression factors/u in the fragmentation process near 0.20. Clear evidence for QCD effects is seen in the average squared transverse momentum ofK0 and Λ particles.
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We report a systematic study of mid-rapidityET production and forward energy flow in the interaction of16O projectiles on Al, Cu, Ag and Au at 60 and 200 GeV/nucleon. First results onET production with32S projectiles are presented.
The production of neutral strange particles (K0, Λ) inp Ar,pXe and\(\bar p\)Xe collisions at 200 GeV is investigated in the NA5 experiment using a streamer chamber at the CERN SPS. Results are presented on inclusive cross sections, average multiplicities, and on rapidity and transverse momentum distributions of neutral strange particles.
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Results on the production of charged hadrons in muon-deuteron and muon-xenon interactions are presented. The data were taken with the E665 spectrometer, which was exposed to the 490 GeV muon beam of the Tevatron at Fermilab. The use of a streamer chamber as vertex detector provides nearly 4π acceptance for charged particles. The μD data are compared with the μXe data in terms of multiplicity distributions, average multiplicities, forward-backward multiplicity correlations, rapidity and transverse momentum distributions and of two-particle rapidity correlations of charged hadrons. The data cover a range of invariant hadronic massesW from 8 to 30 GeV.
Results of negative binomial function fit to the multiplicity distribution of charged hadrons in muon-deuteron scattering. DISPERSION = SQRT(1/MULT + 1/K) is this dispersion of the scaled multiplicity Z = N/MULT.
Results of negative binomial function fit to the multiplicity distribution of charged hadrons in muon-xenon scattering. DISPERSION = SQRT(1/MULT + 1/K) is this dispersion of the scaled multiplicity Z = N/MULT.
Results of negative binomial fits to charged hadron multiplicity distributions in muon-deuteron interactions for backward and forward hemispheres of the hadronic cm.
The transverse momentum and rapidity distributions of net protons and negatively charged hadrons have been measured for minimum bias proton-nucleus and deuteron-gold interactions, as well as central oxygen-gold and sulphur-nucleus collisions at 200 GeV per nucleon. The rapidity density of net protons at midrapidity in central nucleus-nucleus collisions increases both with target mass for sulphur projectiles and with the projectile mass for a gold target. The shape of the rapidity distributions of net protons forward of midrapidity for d+Au and central S+Au collisions is similar. The average rapidity loss is larger than 2 units of rapidity for reactions with the gold target. The transverse momentum spectra of net protons for all reactions can be described by a thermal distribution with `temperatures' between 145 +- 11 MeV (p+S interactions) and 244 +- 43 MeV (central S+Au collisions). The multiplicity of negatively charged hadrons increases with the mass of the colliding system. The shape of the transverse momentum spectra of negatively charged hadrons changes from minimum bias p+p and p+S interactions to p+Au and central nucleus-nucleus collisions. The mean transverse momentum is almost constant in the vicinity of midrapidity and shows little variation with the target and projectile masses. The average number of produced negatively charged hadrons per participant baryon increases slightly from p+p, p+A to central S+S,Ag collisions.
Rapidity distributions of net hyperons (Lambda-Lambdabar) for minimum bias p+Au (1.4 < y < 4.4) collisions at 200 GeV/nucleon.
Rapidity distributions of net hyperons (Lambda-Lambdabar) for minimum bias p+S (1.0 < y < 5.0) collisions at 200 GeV/nucleon.
Rapidity distributions of net hyperons (Lambda-Lambdabar) for central S+Ag (0.5 < y < 3.0) collisions at 200 GeV/nucleon.
We have studied photoproduction using a 1 m streamer chamber at DESY and a tagged photon beam with an energy range of 1.6 GeV < E γ < 6.3 GeV. We analysed approximately 30 000 events and report topological, channel and resonance production cross sections for a large number of reactions with three and five outgoing charged particles.
CORRECTED FOR DECAYS OTHER THAN <PI+ PI- PI0>.
QUASI TWO-BODY REACTIONS ARE NOT INCLUDED IN THE OTHER CORRESPONDING REACTIONS.
QUASI TWO-BODY REACTIONS ARE NOT INCLUDED IN THE OTHER CORRESPONDING REACTIONS. CORRECTED FOR UNOBSERVED DECAY MODES.
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