10,556 research outputs found
Weak Decays of Doubly Heavy Baryons:
The weak decays of a spin- doubly charm baryon () to a
spin- singly charm baryon () and a light vector meson ()
are studied under a phenomenological scheme. The contributions are classified
into different topological diagrams, among which the short distance ones are
calculated under the factorization hypothesis, and the long distance
contributions are modelled as final-state interactions (FSIs) which are
estimated with the one-particle-exchange model. In calculation the topological
contributions tend to fall in a hierarchy. The branching fractions or decay
widths are estimated, and it indicates that
and can be used as candidate
decays for searching and . Some decays that are
mainly activated by the long distance effects are found, observation on which
in future experiments can help to understand the role of FSIs in charm baryon
decays.Comment: 29 pages, 5 figures, 7 tables; version published in EPJ
Characterization of Lifshitz transitions in topological nodal line semimetals
We introduce a two-band model of three-dimensional nodal line semimetals, the
Fermi surface of which at half-filling may form various one-dimensional
configurations of different topology. We study the symmetries and "drumhead"
surface states of the model, and find that the transitions between different
configurations, namely, the Lifshitz transitions, can be identified solely by
the number of gap-closing points on some high-symmetry planes in the Brillouin
zone. A global phase diagram of this model is also obtained accordingly. We
then investigate the effect of some extra terms analogous to a two-dimensional
Rashba-type spin-orbit coupling. The introduced extra terms open a gap for the
nodal line semimetals and can be useful in engineering different topological
insulating phases. We demonstrate that the behavior of surface Dirac cones in
the resulting insulating system has a clear correspondence with the different
configurations of the original nodal lines in the absence of the gap terms.Comment: 7 pages, 6 figure
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