Measurements of charged pion and kaon production in central Pb+Pb collisions at 40, 80 and 158 AGeV are presented. These are compared with data at lower and higher energies as well as with results from p+p interactions. The mean pion multiplicity per wounded nucleon increases approximately linearly with s_NN^1/4 with a change of slope starting in the region 15-40 AGeV. The change from pion suppression with respect to p+p interactions, as observed at low collision energies, to pion enhancement at high energies occurs at about 40 AGeV. A non-monotonic energy dependence of the ratio of K^+ to pi^+ yields is observed, with a maximum close to 40 AGeV and an indication of a nearly constant value at higher energies.The measured dependences may be related to an increase of the entropy production and a decrease of the strangeness to entropy ratio in central Pb+Pb collisions in the low SPS energy range, which is consistent with the hypothesis that a transient state of deconfined matter is created above these energies. Other interpretations of the data are also discussed.
The centrality of the collisions expressed as a percentage of the inelastic cross section (7.15nb), and the mean numbers of wounded nuclei.
The inverse slope parameter of the fitted transverse mass spectra.
The rapidity density averaged over the rapidity interval -0.6 to 0.6.
The neutral π0 and η mesons are studied in 197Au−197Au collisions at an incident energy of 800AMeV, substantially below the threshold for η production in N−N collisions. While the gross π0 multiplicity increases almost linearly with the number of participant nucleons, the multiplicities of η and hard π0 mesons show a stronger than linear dependence. The nonlinearity is governed by the average transverse-mass excess 〈mt〉−(s−2mN) of the mesons and is insensitive to their final-state interaction in the nuclear medium.
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In this letter the distribution of slow target associated particles emitted in Au + Emulsion interactions at 11.6 A GeV/ c is studied. The three models RQMD, FRITIOF and VENUS are used for comparisons and especially their treatment of rescattering is investigated.
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PROJECTILE ASSOCIATED HE-FRAGMENTS.
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The production of neutral pions has been studied in the reactions 40 Ar + nat Ca , 86 Kr + nat Zr and 197 Au + 197 Au at 1 A GeV. For high energy pions emitted from the heavier systems a steeper than linear rise of the pion multiplicity with the centrality of the reaction is observed, indicating a pion production process other than binary nucleon-nucleon collisions. At low transverse momenta an enhancement of the π 0 -multiplicity increasing with the mass of the collision system is found. Systematic discrepancies between the experimental results and recent BUU, QMD and Cascade calculations are discussed.
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RESULTS OF AN EXTRAPOLATION TO THE FULL SOLID ANGLE TAKING THE EXPERIMENTALTEMPERATURES INTO ACCOUNT.
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Production of Λ, Λ , and K s 0 has been measured for a wide range of event multiplicity in S+Pb reactions at 200 GeV/c per nucleon. The production of Λ is shown to increase with multiplicity faster than expected from a superposition of p+p collisions. The effect is seen for low multiplicity (below 100 negative particles).
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Pseudorapidity distributions of relativistic singly charged particles in oxygen-induced emulsion interactions at 14.6, 60, and 200 GeV/nucleon are studied. Limiting fragmentation behavior is observed in both the target and projectile fragmentation regions for a central as well as for a minimum-bias sample. Comparisons with the fritiof model reveal that the picture of fragmenting strings successfully describes the observed data.
NUCLEUS IS AVERAGE NUCLEUS OF EMULSION.
NUCLEUS IS AVERAGE NUCLEUS OF EMULSION.
The inclusive production of Ks0, Λ, Λ¯, and Ks0Λ in the p¯Ta reaction at 4 GeV/c was measured and compared with that in the p¯p reaction. The total inelastic and topological cross sections were also measured. The number of Λ’s produced in the p¯Ta reaction was 11.3 times larger than that expected from the geometrical cross section, which is defined as A2/3 times the cross section for the p¯p reaction. The yield ratio Λ¯/Λ was found to be 2×10−2. These values cannot be accounted for by a straightforward extension of the p¯N reaction. Besides, a correlation of 2 vees like Ks0-Λ could not prove their simultaneous production. Nuclear temperatures of 135 and 97 MeV were obtained from the kinetic energy spectra of Ks0 and Λ, respectively. The kinematical characteristics of the Ks0 and Λ produced were analyzed in terms of the fireball model.
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Central collisions of O16 nuclei with the Ag107 and Br80 nuclei in nuclear emulsion at 14.6, 60, and 200 GeV/nucleon are compared with proton-emulsion data at equivalent energies. The multiplicities of produced charged secondaries are consistent with the predictions of superposition models. At 200 GeV/nucleon the central particle pseudorapidity density is 58±2 for those events with multiplicities exceeding 200 particles.
Nucleus is average nucleus of BR-2 emulsion.
Nucleus is average nucleus of BR-2 emulsion.
Nucleus is average AG107/BR80 nucleus of BR-2 emulsion.
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