5,308 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
Search for single production of the vector-like top partner at the 14 TeV LHC
The new heavy vector-like top partner~() is one of typical features of
many new physics models beyond the standard model. In this paper we study the
discovery potential of the LHC for the vector-like -quark both in the
leptonic and (trilepton) channels at
TeV in the single production mode. Our analysis is based on a
simplified model including a singlet with charge with only two
free parameters, namely the coupling parameter and the top
partner mass . The exclusion limits, evidence and the
discovery reach in the parameter plane of , are,
respectively, obtained for some typical integrated luminosity at the 14 TeV
LHC. Finally we analyze the projected sensitivity in terms of the production
cross section times branching fraction for two decay channel.Comment: 15 pages, 10 figures, 2 tables. version in EPJ
High-Q exterior whispering gallery modes in a metal-coated microresonator
We propose a kind of plasmonic whispering gallery modes highly localized on
the exterior surface of a metal-coated microresonator. This exterior (EX)
surface mode possesses high quality factors at room temperature, and can be
efficiently excited by a tapered fiber. The EX mode can couple to an interior
(IN) mode and this coupling produces a strong anti-crossing behavior, which not
only allows conversion of IN to EX modes, but also forms a long-lived
anti-symmetric mode. As a potential application, the EX mode could be used for
a biosensor with a sensitivity high up to 500 nm per refraction index unit, a
large figure of merit, and a wide detection range
Cavity QED treatment of scattering-induced efficient free-space excitation and collection in high-Q whispering-gallery microcavities
Whispering-gallery microcavity laser possesses ultralow threshold, whereas
convenient free-space optical excitation and collection suffer from low
efficiencies due to its rotational symmetry. Here we analytically study a
three-dimensional microsphere coupled to a nano-sized scatterer in the
framework of quantum optics. It is found that the scatterer is capable of
coupling light in and out of the whispering-gallery modes (WGMs) without
seriously degrading their high-Q properties, while the microsphere itself plays
the role of a lens to focus the input beam on the scatterer and vice versa. Our
analytical results show that (1) the high-Q WGMs can be excited in free space,
and (2) over 50% of the microcavity laser emission can be collected within less
than . This coupling system holds great potential for low
threshold microlasers free of external couplers.Comment: 10 pages, 8 figure
Strongly enhanced light-matter interaction in a hybrid photonic-plasmonic resonator
We propose a hybrid photonic-plasmonic resonant structure which consists of a
metal nanoparticle (MNP) and a whispering gallery mode (WGM) microcavity. It is
found that the hybrid mode enables a strong interaction between the light and
matter, and the single-atom cooperativity is enhanced by more than two orders
of magnitude compared to that in a bare WGM microcavity. This remarkable
improvement originates from two aspects: (1) the MNP offers a highly enhanced
local field in the vicinity of an emitter, and (2), surprisingly, the
high-\textit{Q} property of WGMs can be maintained in the presence of the MNP.
Thus the present system has great advantages over a single microcavity or a
single MNP, and holds great potential in quantum optics, nonlinear optics and
highly sensitive biosening.Comment: 5 pages, 4 figure
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