Evidence of Color Coherence Effects in W+jets Events from ppbar Collisions at sqrt(s) = 1.8 TeV

We report the results of a study of color coherence effects in ppbar collisions based on data collected by the D0 detector during the 1994-1995 run of the Fermilab Tevatron Collider, at a center of mass energy sqrt(s) = 1.8 TeV. Initial-to-final state color interference effects are studied by examining particle distribution patterns in events with a W boson and at least one jet. The data are compared to Monte Carlo simulations with different color coherence implementations and to an analytic modified-leading-logarithm perturbative calculation based on the local parton-hadron duality hypothesis.Comment: 13 pages, 6 figures. Submitted to Physics Letters

Nuclear-matter distributions of halo nuclei from elastic proton scattering in inverse kinematics

Proton-nucleus elastic scattering at intermediate energies, a well-established method for probing nuclear-matter density distributions of stable nuclei, was applied for the first time to exotic nuclei. This method is demonstrated to be an effective means for obtaining accurate and detailed information on the size and radial shape of halo nuclei. Absolute differential cross-sections for small-angle scattering were measured at energies near 700 MeV/u for the neutron-rich helium isotopes \chem{^{6}He} and \chem{^{8}He}, and more recently for the lithium isotopes \chem{^{6}Li}, \chem{^{8}Li}, \chem{^{9}Li} and \chem{^{11}Li}, using He and Li beams provided by the fragment separator FRS at GSI Darmstadt. Experiments were performed in inverse kinematics using the hydrogen-filled ionization chamber IKAR which served simultaneously as target and recoil-proton detector. For deducing nuclear-matter distributions, differential cross-sections calculated with the aid of the Glauber multiple-scattering theory, using various parametrizations for the nucleon density distributions as input, were fitted to the experimental cross-sections. The results on nuclear-matter radii and matter distributions are presented, and the significance of the data for a halo structure is discussed. Nuclear-matter distributions obtained for \chem{^{6}He} and \chem{^{8}He} conform with the concept that both nuclei compose of $\alpha$-particle like cores and significant neutron halos. The matter distribution in \chem{^{11}Li} exhibits, as expected from previous reaction cross-section studies with nuclear targets, the by far most extended halo component of all nuclei being investigated. In addition the present data allow a quantitative comparison of the structure of the He and Li isobares of either the mass number $A=6$ or $A=8$. The measured differential cross-sections have also been used for probing density distributions as predicted from various microscopic calculations. A few examples are presented

Study of the nucleon density distribution of "6He and "8He by proton elastic scattering in inverse kinematics

Nuclear matter distributions of the neutron-rich nuclei "6He and "8He were studied via proton-nucleus scattering in inverse kinematics using the recoil detector IKAR. The differential cross sections for p"4He, p"6He and p"8He elastic scattering were measured with an uncertainty of #+-#2% for the absolute normalization for proton recoil energies from 1 to 20 MeV. The experimental techniques and the data analysis are described and first Glauber calculations presented. Data analysis is still in progress so only preliminary results are given. (orig.)Available from TIB Hannover: RO 801(94-43) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Nucleon distributions of "6He and "8He from intermediate-energy proton elastic scattering in inverse kinematics

Nuclear matter density distributions of "4He and the neutron-rich nuclei "6He and "8He were studied via intermediate-energy proton nucleus scattering in inverse kinematics using the recoil detector IKAR. For these nuclei, differential cross sections for elastic scattering at low momentum transfer were measured with an accuracy of 2% on absolute normalization. The experimental method and the procedure of data analysis are described. Phenomenological and microscopically calculated nuclear matter distributions were related to the measured cross sections with the aid of the Glauber multiple scattering theory. (orig.)13 refs.Available from TIB Hannover: RO 801(95-33) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Nuclear matter distributions in "6He and "8He from small angle pHe scattering in inverse kinematics at intermediate energy

Differential cross sections for p"6He and p"8He elastic scattering have been measured in inverse kinematics at small momentum transfers up to vertical stroke t vertical stroke =0.05 (GeV/c)"2 and projectile energies of about 700 MeV/u. Nuclear matter densities deduced from the data are consistent with the concept that "6He and "8He nuclei have an #alpha#-like core and a significant neutron skin. The r.m.s. radii of the nuclear matter distributions were determined to be R_m("6He)=2.30#+-#0.07 fm and R_m("8He)=2.45#+-#0.07 fm. (orig.)Available from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman