Inclusive cross sections for high energy interactions at 0.9, 2.3, 3.6, and 13.5 GeV/nucleon of O16 with C, CR-39 (C12H18O7), CH2, Al, Cu, Ag, and Pb targets were measured. The total charge-changing cross sections and partial charge-changing cross sections for the production of fragments with charge Z=6 and Z=7 are compared to previous experiments at 60 and 200 GeV/nucleon. The contributions of Coulomb dissociation to the total cross sections are calculated. Using factorization rules the partial electromagnetic cross sections are separated from the nuclear components. Energy dependence of both components are investigated and discussed.
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Enhanced strange particle production, nonstatistical multiplicity fluctuations and two-pion Bose-Einstein correlations were measured in O, S-nucleus reactions at 60 and 200 GeV/nucleon. The results indicate significant collective effects in high-energy nucleus-nucleus collisions.
CENTRAL COLLISIONS.
CENTRAL COLLISIONS.
Product of charged kaons in central S + S and O + Au collisions at 200 GeV/nucleon has been studied in the NA 35 Streamer Chamber experiment. Mean multiplicities and transverse mass distributions were obtained. They were compared with nucleon-nucleon data and with model predictions.
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Mixed transverse(P T ) momentum and rapidity distributions of charged particles produced in 200 GeV/AMU heavy ion collisions are obtained with Magnetic-Interferometric-Emulsion-Chamber ( MAGIC ) by CERN-EMU05 experiments. The P T spectra at different rapidity regions showed no anomalous enhancement of low P T components over a conventional, single exponential function with slope values ranging from 160 to 200 MeV/c.
EVENTS SELECTED FOR THE ANALYSIS ARE THOSE WITH CHARGED MULTIPLICITY MORE THAN 400 FOR CENTRAL S+PB COLLISIONS.
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We have measured the slope parameter of the π 0 electromagnetic form factor by measuring the partial branching ratio of the Dalitz decay π 0 → γe + e − into high-invariant-mass electron-positron pairs. We obtain a value a =0.026 with a total (statistical and systematic) error of ±0.054, in agreement with vector dominance and quark loop calculations.
The PI0 form factor is parameterized as F(M(ee)**2) = 1 + SLOPE*(M(ee)/M(pi))**2. Two metod are used (see text for detail).
The polarization of the proton from the inclusive breakup reaction 1 H( d , p )X at 2.1 GeV was measured at 0°. The results are expressed as the ratio of the proton polarization, P p , to the deuteron beam polarization, P d , κ 0 = P p / P d . The measured values of κ 0 range from +0.983 to -0.305 and are in general agreement with the expected behavior arising from the D state in the deuteron wave function.
POL(C=DEUT) is the DEUT polarization, the P(P=3,RF=ANTILAB) is the proton momentum in DEUT rest frame.
Average numbers of ϱ 0 , K ∗0 (890) and K ∗0 (890) produced in peripheral collisions (with the number of “grey” protons n g ⩽2) of K + with Al and of π + with Al and Au nuclei at 250 GeV/ c are measured in the EHS(NA22) experiment at the CERN SPS. No evidence is found for suppression of vector meson production relative to K + p and π + collisions at the same energy.
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We have measured the cross section for γγ production with the TOPAZ detector in the energy region √ s =50.0–61.4 GeV. The observed cross section for γγ production integrated over |cos θ | ⩽ 0.77 is 50.2±0.8±2.2 pb at 〈√ s 〉=57.6 GeV and the ratio of this value to the QED prediction is 1.01±0.02±0.04. The angular distribution is in good agreement with the QED predictions, thereby setting limits on the compositeness scales, Λ L+R + =168 GeV, Λ L+R − =97 GeV, Λ L,R =141 GeV, Λ L,R − =81 GeV, and Λ L−R ± =68 GeV, at the 95% confidence level. The reaction e + e − → γγγ was also studied and was found consistent with the QED prediction.
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Absolute cross sections for Compton scattering from protons have been determined at 180° for the backscattered photon at incident laboratory photon energies of 98 and 132 MeV. For the difference between the electric and the magnetic polarizability of the proton a value of (7.03 − 2.37 +2.49 − 2.05 +2.14 ) × 10 −4 fm 3 has been derived using the predictions from calculations based on relativistic dispersion relations.
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