Measurements ofKs0, Λ and\(\bar \Lambda \) production in π− nucleus (C, Cu, Pb) interactions are presented. The experiment was carried out with the streamer chamber spectrometer RISK using a π− beam of ∼40 GeV/c and a trigger requiring a secondary charged particle with transverse momentum above 1.1 GeV/c. Production cross sections, relative production rates and distributions of Feynmanx and transverse momentum squared as well as correlations between theV0 and the trigger particle are presented. The results are compared and found to be in agreement withKs0, Λ and\(\bar \Lambda \) data from untriggered π−p and π−C interactions, except for the relative production rate of antilambdas which is about to times larger in high-pt collisions. Our results can be well interpreted within the dual topological unitarization model.
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The real part of the isospin-even forward-scattering amplitude of pion-nucleon scattering has been determined at a pion energy of Tπ=55 MeV by measurement of the elastic scattering of positive and negative pions on protons within the Coulomb-nuclear interference region. The value confirms the prediction of the Karlsruhe-Helsinki phase-shift analysis for that energy. These phases have been used to determine the σ term of pion-nucleon scattering by means of dispersion relations, resulting in a value for σ which is in contradiction with chiral perturbation theory of QCD.
PI- P cross sections normalised to the Coulomb cross section taken from the Karlesruhe-Helsinki phase shift analysis (R. Koch, E. Pietarinen (NP A336(80)331).
Total and annihilation n¯p cross sections from 100 to 500 MeV/c are reported, the first such measurements with good statistics in this momentum range. These cross sections are well represented by A+B/p, where p is the incident antineutron momentum, and are in agreement with previous n¯p and p¯n measurements. A comparison of these cross sections with phenomenological potential model calculations is good overall. However, the microscopic quark model gives unsatisfactory predictions. The agreement between previous p¯p annihilation cross sections and n¯p cross sections above 300 MeV/c is excellent. The total n¯p cross section is lower than the total p¯p cross section in this momentum range. Both of these types of behavior are predicted by potential models. The anticipated availability of future p¯p data below 300 MeV/c should indicate whether these trends continue at lower momenta.
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p̄p total cross sections have been measured from 220 to 413 MeV/ c in small (⩽ 10 MeV/ c ) steps of momentum with statistics of ± 0.5 %. There is no evidence for structure in the cross section, and a limit of 8 mb MeV/ c 2 is set with 90% confidence on the strength of any narrow resonance down to 250 MeV/ c .
Data taken with long target.
Data taken with short target.
Results are presented from reactions of 60 A GeV and 200 A GeV 16 O projectiles with C, Cu, Ag, and Au nuclei. Energy spectra measured at zero degrees and transverse energy distributions in the pseudorapidity range from 2.4 to 5.5 are shown. The average transverse energy per participant is found to be nearly independent of target mass. Estimates of nuclear stopping and of attained energy densities are made.
STOPPING POWER IS THE QUANTITY GIVEN IN THIS TABLE. IT IS DEFINED AS ( D(ET(EXP)/D(ETA) / D(ET(THEORY)/D(ETA) ) AND THE DENOMINATOR IS TAKEN TO BE 0.5*E(HADRON IN CM). ETA IS THE PSEUDO-RAPIDITY.
We present inclusive ¶ and K *0 (892) cross sections and Feynman x -spectra in K + p collisions at 250 GeV/ c . In the K + fragmentation region, x > 0.2, the ratio of ¶ to K *0 (892) is used to estimate the strangeness suppression factor λ , with the result γ =0.17 ± 0.02 (stat ± 0.01 (syst). We see no evidence for an energy dependence of λ in the CM energy range 7.8 ≤ s ≤21.7 GeV.
RESULTS AT 32 AND 70 GEV INCLUDED FOR COMPARISON.
RESULTS AT 32 AND 70 GEV INCLUDED FOR COMPARISON.
RESULTS AT 32 AND 70 GEV INCLUDED FOR COMPARISON.
Inclusive data are presented on ϱ 0 ,ϱ + and ω produced in k + p interactions at 250 GeV/ c , for ϱ + and ω for the first time in K + p experiment. In the forward CM hemisphere, the ϱ + , ϱ 0 and ω differential production rates are equal within errors, and remarkably similar to muon-inelastic scattering data on ϱ 0 and ω at 280 GeV/ c .
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The polarization of Σ 0 hyperons produced in an inclusive reactons hasbeen measured for the first time. From a sample of 11 000 events produced by 28.5 GeV/ c ptorons in the reaction p+ Be → Σ 0 +X, the Σ 0 polarization has a value of +0.28±0.13 at p t =1.01 GeV/ c and x f =0.60. The polarization of 53 000 Λ hyperons produced from 28.5 Gev/ c protons inthe reaction p+Be→ Λ +X has been measured in the kinematic range 0.64< p t <1.14 GeV/ c and 0.42< x f <0.62. The average Λ polarization is found to be −0.188±0.024, consistent with previous results.
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