2,963 research outputs found
Unitarity Quadrangles of Four Neutrino Mixing
We present a classification of the unitarity quadrangles in the four-neutrino
mixing scheme. We find that there are totally thirty-six distinct topologies
among twelve different unitarity quadrangles. Concise relations are established
between the areas of those unitarity quadrangles and the rephasing invariants
of CP and violation.Comment: RevTex 10 pages. Minor changes made. Accepted for publication in
Phys. Rev.
Enhancement of Dark Matter Annihilation via Breit-Wigner Resonance
The Breit-Wigner enhancement of the thermally averaged annihilation cross
section is shown to provide a large boost factor when the dark
matter annihilation process nears a narrow resonance. We explicitly demonstrate
the evolution behavior of the Breit-Wigner enhanced as the function
of universe temperature for both the physical and unphysical pole cases. It is
found that both of the cases can lead an enough large boost factor to explain
the recent PAMELA, ATIC and PPB-BETS anomalies. We also calculate the coupling
of annihilation process, which is useful for an appropriate model building to
give the desired dark matter relic density.Comment: 4 pages, 4 figures, references added, accepted for publication in
Physical Review
Direct detection and solar capture of dark matter with momentum and velocity dependent elastic scattering
We explore the momentum and velocity dependent elastic scattering between the
dark matter (DM) particles and the nuclei in detectors and the Sun. In terms of
the non-relativistic effective theory, we phenomenologically discuss ten kinds
of momentum and velocity dependent DM-nucleus interactions and recalculate the
corresponding upper limits on the spin-independent DM-nucleon scattering cross
section from the current direct detection experiments. The DM solar capture
rate is calculated for each interaction. Our numerical results show that the
momentum and velocity dependent cases can give larger solar capture rate than
the usual contact interaction case for almost the whole parameter space. On the
other hand, we deduce the Super-Kamiokande's constraints on the solar capture
rate for eight typical DM annihilation channels. In contrast to the usual
contact interaction, the Super-Kamiokande and IceCube experiments can give more
stringent limits on the DM-nucleon elastic scattering cross section than the
current direct detection experiments for several momentum and velocity
dependent DM-nucleus interactions. In addition, we investigate the mediator
mass's effect on the DM elastic scattering cross section and solar capture
rate.Comment: 18 pages, 4 figures, 2 tables. minor changes and a reference added,
published in Nuclear Physics
Object Discovery via Cohesion Measurement
Color and intensity are two important components in an image. Usually, groups
of image pixels, which are similar in color or intensity, are an informative
representation for an object. They are therefore particularly suitable for
computer vision tasks, such as saliency detection and object proposal
generation. However, image pixels, which share a similar real-world color, may
be quite different since colors are often distorted by intensity. In this
paper, we reinvestigate the affinity matrices originally used in image
segmentation methods based on spectral clustering. A new affinity matrix, which
is robust to color distortions, is formulated for object discovery. Moreover, a
Cohesion Measurement (CM) for object regions is also derived based on the
formulated affinity matrix. Based on the new Cohesion Measurement, a novel
object discovery method is proposed to discover objects latent in an image by
utilizing the eigenvectors of the affinity matrix. Then we apply the proposed
method to both saliency detection and object proposal generation. Experimental
results on several evaluation benchmarks demonstrate that the proposed CM based
method has achieved promising performance for these two tasks.Comment: 14 pages, 14 figure
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