Tensor polarization observables ( t(20), t(21), and t(22)) have been measured in elastic electron-deuteron scattering for six values of momentum transfer between 0.66 and 1.7 (GeV/c)(2). The ...experiment was performed at the Jefferson Laboratory in Hall C using the electron High Momentum Spectrometer, a specially designed deuteron magnetic channel and the recoil deuteron polarimeter POLDER. The new data determine to much larger Q2 the deuteron charge form factors G(C) and G(Q). They are in good agreement with relativistic calculations and disagree with perturbative QCD predictions.
A rigorous extraction of the deuteron charge form factors from tensor polarization data in elastic electron-deuteron scattering, at given values of the 4-momentum transfer, is presented. Then the ...world data for elastic electron-deuteron scattering is used to parameterize, in three different ways, the three electromagnetic form factors of the deuteron in the 4-momentum transfer range 0-7 fm^-1. This procedure is made possible with the advent of recent polarization measurements. The parameterizations allow a phenomenological characterization of the deuteron electromagnetic structure. They can be used to remove ambiguities in the form factors extraction from future polarization data.
The A(Q^2) structure function in elastic electron-deuteron scattering was measured at six momentum transfers Q^2 between 0.66 and 1.80 (GeV/c)^2 in Hall C at Jefferson Laboratory. The scattered ...electrons and recoil deuterons were detected in coincidence, at a fixed deuteron angle of 60.5 degrees. These new precise measurements resolve discrepancies between older sets of data. They put significant constraints on existing models of the deuteron electromagnetic structure, and on the strength of isoscalar meson exchange currents.
Direct measurements of total reaction cross sections (sigma R) have been performed in the energy range of 10-300 MeV/nucleon for heavy ion collisions. A decrease of sigma R with increasing energy was ...observed for a wide range of masses of the colliding systems. The data suggest that sigma R reaches a minimum located around 300 MeV/nucleon independently of the projectile target combination. A dependence of sigma R on mass asymmetry of the svstem is also demonstrated. Trends of sigma R in this energy range are well reproduced by the predictions of a simple microscopic model based on individual nucleon-nucleon collisions. Our data have been employed in this framework to derive a new semi-empirical parametrization of sigma R. Most of the experimental results in the intermediate and high energy range have been reproduced by this parametrization using a single energy-dependent parameter.
We have studied the quasielastic 3He(e,e'p)2H reaction in perpendicular coplanar kinematics, with the energy and the momentum transferred by the electron fixed at 840 MeV and 1502 MeV/c, ...respectively. The 3He(e,e'p)2H cross section was measured for missing momenta up to 1000 MeV/c, while the ATL asymmetry was extracted for missing momenta up to 660 MeV/c. For missing momenta up to 150 MeV/c, the cross section is described by variational calculations using modern 3He wave functions. For missing momenta from 150 to 750 MeV/c, strong final-state interaction effects are observed. Near 1000 MeV/c, the experimental cross section is more than an order of magnitude larger than predicted by available theories. The ATL asymmetry displays characteristic features of broken factorization with a structure that is similar to that generated by available models.
The strength of the neutron-neutron correlation function from the E=45A MeV Ni-58+Al-27, Ni-nat, and Au-197 reactions depends on the neutron parallel velocity. This indicates the presence of multiple ...sources of neutron emission. We find these sources consistent with a dissipative, binary reaction mechanism as it is described by, e.g., Boltzmann-Uehling-Uhlenbeck calculations.
In elastic electron-deuteron scattering, the tensor polarization moments
t
20,
t
21 and
t
22, together with the unpolarized cross-sections, have been measured up to a momentum transfer of 1.8 (GeV/c)
...2, or 6.8 fm
−1. The experiment was performed at Jefferson Laboratory using the recoil deuteron polarimeter POLDER. Preliminary results are presented and discussed, especially in view of their significance concerning the applicability of perturbative QCD to this exclusive process.
Azimuthal angle correlations have been measured for Li-Li pairs from sup 40Ar + sup 197Au, sup natAg, sup natCu, sup 27Al (17ital A, 27ital A, and 34ital A MeV). Many of these correlations exhibit ...enhancements at Deltaital cphi of 0degree and 180degree, the classical pattern for evaporation from a hot, high-spin source. A very different pattern is predicted by a simple multifragmentation model, i.e., a peak at Deltaital cphiapprox60degree. This peak is driven by the rapid Coulomb explosion of a nonrotating nucleus. The latter pattern is not observed experimentally, however, if collective rotation is included in the multifragmentation model, its predictions are more consistent with the observations. Such comparisons can give a promising test for sequential emission from a rotating source versus instantaneous explosive multifragmentation, but one needs a very good selection of collision centrality to reduce the role of the collective rotation. For most of these data the dominant driving forces seem to be rotational motion perturbed by final-state Coulomb repulsions for time delays of the order of 10sup minus22 s between successive emissions of Li fragments.
PDF
