4,544 research outputs found

    Editors’ Notes

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    Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149556/1/he20319_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149556/2/he20319.pd

    Change of nuclear configurations in the neutrinoless double-β\beta decay of 130^{130}Te →\rightarrow 130^{130}Xe and 136^{136}Xe →\rightarrow 136^{136}Ba

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    The change in the configuration of valence protons between the initial and final states in the neutrinoless double-β\beta decay of 130^{130}Te →\rightarrow 130^{130}Xe and of 136^{136}Xe →\rightarrow 136^{136}Ba has been determined by measuring the cross sections of the (dd,3^3He) reaction with 101-MeV deuterons. Together with our recent determination of the relevant neutron configurations involved in the process, a quantitative comparison with the latest shell-model and interacting-boson-model calculations reveals significant discrepancies. These are the same calculations used to determine the nuclear matrix elements governing the rate of neutrinoless double-β\beta decay in these systems.Comment: 10 pages, 4 figures, 9 table

    Spatial Current Patterns, Dephasing and Current Imaging in Graphene Nanoribbons

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    Using the non-equilibrium Keldysh Green's function formalism, we investigate the local, non-equilibrium charge transport in graphene nanoribbons (GNRs). In particular, we demonstrate that the spatial current patterns associated with discrete transmission resonances sensitively depend on the GNRs' geometry, size, and aspect ratio, the location and number of leads, and the presence of dephasing. We identify a relation between the spatial form of the current patterns, and the number of degenerate energy states participating in the charge transport. Furthermore, we demonstrate a principle of superposition for the conductance and spatial current patterns in multiple-lead configurations. We demonstrate that scanning tunneling microscopy (STM) can be employed to image spatial current paths in GNR with atomic resolution, providing important insight into the form of local charge transport. Finally, we investigate the effects of dephasing on the spatial current patterns, and show that with decreasing dephasing time, the current patterns evolve smoothly from those of a ballistic quantum network to those of classical resistor network.Comment: 25 pages, 12 figure

    Quasielastic 12C(e,e'p) Reaction at High Momentum Transfer

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    We measured the 12C(e,e'p) cross section as a function of missing energy in parallel kinematics for (q,w) = (970 MeV/c, 330 MeV) and (990 MeV/c, 475 MeV). At w=475 MeV, at the maximum of the quasielastic peak, there is a large continuum (E_m > 50 MeV) cross section extending out to the deepest missing energy measured, amounting to almost 50% of the measured cross section. The ratio of data to DWIA calculation is 0.4 for both the p- and s-shells. At w=330 MeV, well below the maximum of the quasielastic peak, the continuum cross section is much smaller and the ratio of data to DWIA calculation is 0.85 for the p-shell and 1.0 for the s-shell. We infer that one or more mechanisms that increase with ω\omega transform some of the single-nucleon-knockout into multinucleon knockout, decreasing the valence knockout cross section and increasing the continuum cross section.Comment: 14 pages, 7 figures, Revtex (multicol, prc and aps styles), to appear in Phys Rev

    Cooperative damping mechanism of the resonance in the nuclear photoabsorption

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    We propose a resonance damping mechanism to explain the disappearance of the peaks around the position of the resonances higher than the Δ\Delta resonance in the nuclear photoabsorption. This phenomenon is understood by taking into account the cooperative effect of the collision broadening of Δ\Delta and N∗N^{*}, the pion distortion and the interference in the two-pion photoproduction processes in the nuclear medium.Comment: 11 pages, uses revtex.sty. To appear in Phys. Rev. Let

    The reaction dynamics of the 16O(e,e'p) cross section at high missing energies

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    We measured the cross section and response functions (R_L, R_T, and R_LT) for the 16O(e,e'p) reaction in quasielastic kinematics for missing energies 25 <= E_miss <= 120 MeV at various missing momenta P_miss <= 340 MeV/c. For 25 < E_miss < 50 MeV and P_miss \approx 60 MeV/c, the reaction is dominated by single-nucleon knockout from the 1s1/2-state. At larger P_miss, the single-particle aspects are increasingly masked by more complicated processes. For E_miss > 60 MeV and P_miss > 200 MeV/c, the cross section is relatively constant. Calculations which include contributions from pion exchange currents, isobar currents and short-range correlations account for the shape and the transversity but only for half of the magnitude of the measured cross section.Comment: 6 pages, 4 figures, submitted to Phys Rev Lett, formatting error fixe
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