Transverse mass and rapidity distributions for charged pions, charged kaons, protons, and antiprotons are reported for square root of [sNN]=200 GeV pp and Au+Au collisions at Relativistic Heary Ion Collider (RHIC). Chemical and kinetic equilibrium model fits to our data reveal strong radial flow and long duration from chemical to kinetic freeze-out in central Au+Au collisions. The chemical freeze-out temperature appears to be independent of initial conditions at RHIC energies.
We studied simultaneously the 4 He(e, e p), 4 He(e, e pp), and 4 He(e, e pn) reactions at Q 2 = 2 (GeV/c) 2 and xB > 1, for an (e, e p) missing-momentum range of 400 to 830 MeV/c. The knocked-out proton was detected in coincidence with a proton or neutron recoiling almost back to back to the missing momentum, leaving the residual A = 2 system at low excitation energy. These data were used to identify two-nucleon short-range correlated pairs and to deduce their isospin structure as a function of missing momentum, in a region where the nucleon-nucleon (N N ) force is expected to change from predominantly tensor to repulsive. The abundance of neutron-proton pairs is reduced as the nucleon momentum increases beyond ∼500 MeV/c. The extracted fraction of proton-proton pairs is small and almost independent of the missing momentum. Our data are compared with calculations of two-nucleon momentum distributions in 4 He and discussed in the context of probing the elusive repulsive N N force.
We report new measurements of the ratio of the electric form factor to the magnetic form factor of the neutron, G n E /G n M , obtained via recoil polarimetry from the quasielastic 2 H( e, e ′ n) 1 H reaction at Q 2 values of 0.45, 1.13, and 1.45 (GeV/c) 2 with relative statistical uncertainties of 7.6 and 8.4% at the two higher Q 2 points, which were not reached previously via polarization measurements. Scale and systematic uncertainties are small.
At 200, 300, and 400 MeV bombarding energies, we measured cross section angular distributions for the Li(p, n) Be(g.s. +0.43 MeV) reaction and 0' cross sections for the ' C(p, n)' N(g. s.) reaction.Systematics of these reactions are presented.The center-of-mass cross section for the Li(p, n) Be(g.s. +0.43 MeV) reaction, when plotted as a function of momentum transfer, is nearly independent of energy. The laboratory cross section for this reaction at 0' in the energy range from 60 to 400 MeV is also independent of energy, having a constant value, to within experimental errors, of 35.5 mb/sr with an estimated uncertainty of +1.5 mb/sr.
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