2,879 research outputs found
Enhanced breaking of heavy quark spin symmetry
Heavy quark spin symmetry is useful to make predictions on ratios of decay or
production rates of systems involving heavy quarks. The breaking of spin
symmetry is generally of the order of , with
the scale of QCD and the heavy quark mass. In this
paper, we will show that a small - and -wave mixing in the wave function
of the heavy quarkonium could induce a large breaking in the ratios of partial
decay widths. As an example, we consider the decays of the
into the , which were recently measured by the
Belle Collaboration. These decays exhibit a huge breaking of the spin symmetry
relation were the a pure bottomonium state. We propose
that this could be a consequence of a mixing of the -wave and -wave
components in the . Prediction on the ratio
is presented assuming that the decay of the -wave component is dominated by
the coupled-channel effects.Comment: 13 pages, 5 figures. Discussion extended, version to appear in
Phys.Lett.
Mass Spectra and Semileptonic Decays of Doubly Heavy and Baryons
In the framework of a non-relativistic quark model, the mass spectra of the
ground and excited states of doubly heavy and baryons are
calculated.
We estimate the mass difference between the and corresponding baryons as MeV for all the states
containing , or quarks.
A simple form of the universal Isgur-Wise function, as the transition form
factor between the doubly heavy baryons, is introduced. Working in the
close-to-zero recoil limit, we investigate the semileptonic
decay widths and branching fractions of the doubly heavy baryons. The obtained
results are compared with other theoretical predictions.Comment: 11 pages, 4 figures and 5 table
RGB-D Salient Object Detection: A Survey
Salient object detection (SOD), which simulates the human visual perception
system to locate the most attractive object(s) in a scene, has been widely
applied to various computer vision tasks. Now, with the advent of depth
sensors, depth maps with affluent spatial information that can be beneficial in
boosting the performance of SOD, can easily be captured. Although various RGB-D
based SOD models with promising performance have been proposed over the past
several years, an in-depth understanding of these models and challenges in this
topic remains lacking. In this paper, we provide a comprehensive survey of
RGB-D based SOD models from various perspectives, and review related benchmark
datasets in detail. Further, considering that the light field can also provide
depth maps, we review SOD models and popular benchmark datasets from this
domain as well. Moreover, to investigate the SOD ability of existing models, we
carry out a comprehensive evaluation, as well as attribute-based evaluation of
several representative RGB-D based SOD models. Finally, we discuss several
challenges and open directions of RGB-D based SOD for future research. All
collected models, benchmark datasets, source code links, datasets constructed
for attribute-based evaluation, and codes for evaluation will be made publicly
available at https://github.com/taozh2017/RGBDSODsurveyComment: 24 pages, 12 figures. Has been accepted by Computational Visual Medi
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