16,383 research outputs found

    Effect of sea quarks on the single-spin asymmetries ALW±A^{W^{\pm}}_{L} in polarized pp collisions at RHIC

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    We calculate the single-spin asymmetries ALW±A^{W^{\pm}}_{L} of W±W^{\pm} bosons produced in polarized pp collisions with the valence part of the up and down quark helicity distributions modeled by the light-cone quark-spectator-diquark model while the sea part helicity distributions of the up and down quarks treated as parametrization. Comparing our results with those from experimental data at RHIC, we find that the helicity distributions of sea quarks play an important role in the determination of the shapes of ALW±A^{W^{\pm}}_{L}. It is shown that ALWA^{W^{-}}_{L} is sensitive to Δuˉ\Delta \bar u, while ALW+A^{W^{+}}_{L} to Δdˉ\Delta \bar d intuitively. The experimental data of the polarized structure functions and the sum of helicities are also important to constrain the sizes of quark helicity distributions both for the sea part and the valence part of the nucleon.Comment: 19 latex pages, 5 figures, final version for publicatio

    Zener Tunneling in Semiconducting Nanotube and Graphene Nanoribbon p-n Junctions

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    A theory is developed for interband tunneling in semiconducting carbon nanotube and graphene nanoribbon p-n junction diodes. Characteristic length and energy scales that dictate the tunneling probabilities and currents are evaluated. By comparing the Zener tunneling processes in these structures to traditional group IV and III-V semiconductors, it is proved that for identical bandgaps, carbon based 1D structures have higher tunneling probabilities. The high tunneling current magnitudes for 1D carbon structures suggest the distinct feasibility of high-performance tunneling-based field-effect transistors.Comment: 4 Pages, 2 Figure