8309896
Photonuclear fission from high energy electrons from ultraintense laser-solid interactions
A new regime of laser-matter interactions in which the quiver motion of plasma electrons is fully relativistic, with energies extending well above the threshold for nuclear processes, is studied using a petawatt laser system. In solid target experiments with focused intensities exceeding 10(20) W/cm(2), high energy electron generation, hard bremsstrahlung, and nuclear phenomena have been observed. We report here a quantitative comparison of the high energy electrons and the bremsstrahlung spectrum, as measured by photonuclear reaction yields, including the photoinduced fission of 238U.
117907932
Observation of Structure in the $\Upsilon$ Region
The properties of the dimuon enhancement seen in 400-GeV proton-nucleus collisions have been clarified by a threefold increase in data. We find two peaks whose widths are consistent with our resolution: M/sub 1/ = 9.4 GeV with dsigma/dy vertical-bar /sub y/ = 1.8 x 10/sup -37/ cm/sup 2//nucleon and M/sub 2/ = 10.0 GeV with Bdsigma/dy vertical-bar /sub y/ = 0.7 x 10/sup -37/ cm/sup 2//nucleon. Evidence for the possible existence of a third peak near 10.4 GeV is discussed as are the comparison with the properties of a qq-bar system, where q is a new heavy quark.
122926539
Longitudinal-Transverse Separation for Inclusive Electroproduction of Pions and Protons
We use new measurements of the inclusive electroproduction reactions eN ..-->.. e'..pi../sup plus-or-minus/X and eN ..-->.. e'pX with epsilon values in the range 0.35 < epsilon < 0.45 together with earlier measurements with 0.85 < epsilon < 0.95 to determine the contributions to the cross section due to transversely and longitudinally polarized photons in the range 1.2 GeV/sup 2/ < Q/sup 2/ < 3.3GeV/sup 2/. The longitudinal component is small and consistent with that observed in the total virtual-photoproduction cross section.
123291162
Measurements of inclusive pion electroproduction
Abstract Measurements of the inclusive pion electroproduction reaction e − +p → e − + π ± +X made at the Wilson Synchrotron Laboratory are reported. Data were taken at points with nominal ( Q 2 , W ) values of (0.6, 2.67), (1.2, 2.67), (2.0, 2.67) and (1.2, 2.15) in (GeV 2 , GeV). A more complete angular distribution was taken at (1.2, 2.67). The virtual photoproduction cross section for π + + missing mass is studied as a function of missing mass, Feynman scaling variables, Q 2 and W . The invariant cross section show a simple behavior as a function of Q 2 and W . Its dependenc on P ⊥ 2 , x ′ and φ is determined.
120186420
Electroproduction of $K^+$ mesons along the virtual photon direction
We report measurements of kaon electroproduction from hydrogen and deuterium targets carried out at the Wilson Synchrotron Laboratory at Cornell University. The reactions ..gamma../sub V/p ..-->.. K/sup +/X/sup 0/, K/sup +/..lambda.., and K/sup +/..sigma../sup 0/ were studied in the kinematic region 2.15 .. 0 as Q/sup 2/ increases.
117500267
A new Mtest beamline for the 1999 fixed target run
28110065
Kaon production from hot and dense matter formed in heavy-ion collisions.
In heavy-ion collisions, kaons can be produced from baryon-baryon, meson-baryon, and meson-meson interactions. Simple meson-exchange models are introduced to study kaon production from these processes in the free space. These models are then extended to determine kaon production in hot, dense nuclear matter by taking into account the decreasing hadron masses as a result of the restoration of chiral symmetry and the condensation of kaons. We find that the cross sections for kaon production from all three processes are enhanced. In particular, the effect of decreasing hadron masses on kaon production from the meson-meson annihilation is most significant. In the hydrochemical model for heavy-ion collisions, we demonstrate that the observed enhancement of kaon yield in high-energy heavy-ion collisions can be explained if the medium effect is included.
42999511
Effect of chiral restoration on kaon production in relativistic heavy-ion collisions.
Kaon production from meson-meson annihilation is enhanced significantly because of the decrease of hadron masses in hot and dense matter as a result of the restoration of chiral symmetry. We show that this can lead to enhanced kaon yield in high-energy heavy-ion collisions.
42270711
Transition densities in 30Si studied by electron scattering and coupled-channel calculations of 650 MeV proton scattering.
Proton and neutron transition densities in $^{30}\mathrm{Si}$ are examined by a combination of intermediate energy (e,e') and (p,p') reactions and mirror electromagnetic transition rates. This analysis is performed for the ${2}_{1}^{+}$ and ${2}_{2}^{+}$ states at 2.234 and 3.499 MeV in $^{30}\mathrm{Si}$. Electron scattering data are presented for these states. Shell-model calculations for the proton and neutron transition matrix elements and proton transition densities are compared with the electromagnetic results. The proton transition densities are reasonably predicted for the ${2}_{1}^{+}$ state but are not adequately predicted for the ${2}_{2}^{+}$ state. A microscopic coupled-channel calculation of 650 MeV (p,p') is used to test the shell-model isoscalar transition densities. Given the uncertainties present in the reaction calculation and interaction, the isoscalar density for the ${2}_{1}^{+}$ state is found to be adequate, but the density for the ${2}_{2}^{+}$ state is less accurate. The coupled-channel effect is shown to be important for the ${2}_{2}^{+}$ state. This dependence increases with energy but should be taken into account for an accurate description of (p,p') reactions at all energies.
39044560
Neutron halos in the Na isotopes.
The neutron and proton density distributions of the Na isotopes out to the proton and neutron drip lines are calculated in the spherical Hartree-Fock model with a wide variety of density-dependent Skyrme interactions. The results are compared to recent experimental data for the interaction cross sections and for the rms radii. We discuss the role of the deformed intruder states and the problems associated with predicting the location of the neutron drip line for this mass region. {copyright} {ital 1996 The American Physical Society.}
46635156
Isovector M1 transitions in 28Si and the role of meson exchange currents.
At the newly installed 180{degree} Darmstadt electron scattering facility we have measured the isovector {ital M}1 transition strengths in {sup 28}Si in the excitation energy range from 10 to 18 MeV. Overall agreement with a shell-model calculation using the unified {ital sd}-shell interaction and effective {ital g} factors is obtained. Comparison with Gamow-Teller strength deduced from ({ital p},{ital n}) data reveals the presence of meson exchange current contributions of the order of 25{percent} to the summed {ital M}1 transition strength. {copyright} {ital 1996 The American Physical Society.}