8,088 research outputs found
Dominant Spin-Flip Effects for the Hadronic Produced Polarization at TEVATRON
Dominant spin-flip effects for the direct and prompt polarizations
at TEVATRON run II with collision energy 1.96 TeV and rapidity cut
, have been systematically studied, especially, the spin-flip
effect for the transition of into has been
carefully discussed. It is found that the spin-flip effect shall always dilute
the polarization, and with a suitable choice of the parameters
and , the polarization puzzle can be solved to a
certain degree. At large transverse momentum , for the prompt
is reduced by for and by for .
We also study the indirect polarization from the -decays, which
however is slightly affected by the same spin-flip effect and then shall
provide a better platform to determine the color-octet matrix elements.Comment: 19 pages, 5 figures. References added. Revised version to be
published in Phys.Rev.
Zener Tunneling in Semiconducting Nanotube and Graphene Nanoribbon p-n Junctions
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
Max-margin Metric Learning for Speaker Recognition
Probabilistic linear discriminant analysis (PLDA) is a popular normalization
approach for the i-vector model, and has delivered state-of-the-art performance
in speaker recognition. A potential problem of the PLDA model, however, is that
it essentially assumes Gaussian distributions over speaker vectors, which is
not always true in practice. Additionally, the objective function is not
directly related to the goal of the task, e.g., discriminating true speakers
and imposters. In this paper, we propose a max-margin metric learning approach
to solve the problems. It learns a linear transform with a criterion that the
margin between target and imposter trials are maximized. Experiments conducted
on the SRE08 core test show that compared to PLDA, the new approach can obtain
comparable or even better performance, though the scoring is simply a cosine
computation
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