A liquid hydrogen target was used to study the nuclear fragmentation of beams of relativistic heavy ions, Ne22 to Ni58, over an energy range 400 to 900 MeV/nucleon. The experiments were carried out at the Lawrence Berkeley Laboratory Bevalac HISS facility, using the charge-velocity-rigidity method to identify the charged fragments. Here we describe the general concept of the experiment and present total charge-changing cross sections obtained from 17 separate runs. These new measured cross sections display an energy dependence which follows semiempirical model predictions. The mass dependence of the cross sections behaves as predicted by optical models, but within the experimental energy range, the optical model parameters display a clear energy dependence. The isospin of the projectile nuclei also appears to be an important factor in the interaction process.
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We present a total of 191 and 203 data points of the elastic neutron-protonspin correlation parameters A ookk and A oosk , respectively. Both observables were measured in a large angular interval. The observable A ookk was measured from 0.312 to 1.10 GeV and A oosk from 0.80 to 1.10 GeV. The SATURNE II polarized beam of free neutrons obtained from the break-up of polarized deuterons was scattered on the polarized Saclay frozen-spin proton target. The beam polarization was oriented either along the beam direction or sideways, the target polarization was oriented longitudinally. Data are compared with phase-shift analyses predictions and with the PSI, LAMPF and SATURNE II results. Present results provide an important contribution to any future theoretical or phenomenological analysis.
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The spin-dependent structure function g 1 p has been measured by deep inelastic scattering of polarized muons off polarized protons at 190 GeV incident muon energy. The data cover a kinematic range of 1 < Q 2 < 80 GeV 2 and 0.003 < x < 0.6, where −Q 2 is the squared 4-momentum transfer and x is the Biorken scaling variable. The first moment Γ 1 p = ∫ 0 1 g 1 p d x = 0.152 ± 0.015( stat. ) ± 0.018( syst. ) is smaller than the prediction of the Ellis-Jaffe sum rule by one standard deviation. This result leads to a contribution of the quark spins to the proton spin of δΣ = 0.36 ± 0.21. All results presented here are preliminary.
First moment of the spin-dependent structure function G1.
We have measured the polarization of Λ and Λ hyperons produced by 800 GeV protons on a Be target at a fixed targeting angle of 4.8 mrad. Comparison with previous data at 400 GeV production energy and twice the targeting angle shows no significant energy dependence for the Λ polarization. This is in striking contrast to the energy dependence found for σ + and Ξ − polarizations. We find no evidence for Λ polarization at 800 GeV.
Errors are combined statistics and systematics.
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We have studied single photon production in e + e − annihilation based on a data sample corresponding to an integrated luminosity of 164.1 pb −1 at s =58 GeV . The single photon yield is consistent with the prediction of the standard model with three light neutrino species. No anomalous signal has been observed. From this result left- and right-handed scalar electrons in the mass degenerate case are excluded at 90% CL below 44.4 GeV/ c 2 for the massless photino.
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NET BARYON DENSITY D(N)/D(Y) HAS BEEN DETERMINED AT THE RAPIDITY OF NN C.M.S., FOR NET BARYON THE FORMULAR: 2*(P-PBAR)+1.6*(LAMBDA- LAMBDABAR) HAS BEEN USED.
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Annihilation cross-sections σann for antineutrons on some nuclei (C, Al, Cu, Sn and Pb) at three antineutron momenta (180, 240 and 280 MeV/c) were measured at LEAR (CERN) with the OBELIX spectrometer. A behaviour σann=σ0Aν has been found withν≈2/3. The data are discussed following some models for antineutron-nucleus interaction.
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In this paper the main experimental results on some significant physical quantities obtained in He−Li collisions at 4.5A GeV/c are presented. The experiments have been performed at the Syncrophasotron from JINR Dubna, in the frame of the SKM 200 Collaboration.
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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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The doubly-differential cross sections for the pp → ppη and pd → ηX reactions have been measured at incident proton energies of 1.3 and 1.5 GeV. The ratio of the pd to pp -induced cross sections varies from about 8–10 at 1.3 GeV to 4.5–6 at 1.5 GeV in the η kinetic energy interval 100 MeV ⩽ T η ⩽220 MeV. Information on the pn → ηX reaction has been extracted from these measurements within the framework of a simple folding model.
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