2,237 research outputs found
violation in charmed hadron decays into neutral kaons
We find a new violating effect in charmed hadron decays into neutral
kaons, which is induced by the interference between the Cabibbo-favored and
doubly Cabibbo-suppressed amplitudes with the mixing.
It is estimated to be of order of , much larger than the
direct asymmetry, but missed in the literature. To reveal this new
violation effect, we propose a new observable, the difference of the
asymmetries in the and
modes. Once the new effect is determined by experiments, the direct
asymmetry then can be extracted and used to search for new physics.Comment: 6 pages, 3 figures. Contribution to the proceeding of The 15th
International Conference on Flavor Physics & CP Violation, 5-9 June 2017,
Prague, Czech Republi
Implications on the first observation of charm CPV at LHCb
Very recently, the LHCb Collaboration observed the violation (CPV) in
the charm sector for the first time, with .
This result is consistent with our prediction of obtained in the factorization-assisted
topological-amplitude (FAT) approach in [PRD86,036012(2012)]. It implies that
the current understanding of the penguin dynamics in charm decays in the
Standard Model is reasonable. Motivated by the success of the FAT approach, we
further suggest to measure the decay, which is the next
potential mode to reveal the CPV of the same order as .Comment: 10 page
Branching ratios and direct CP asymmetries in decays
We propose a theoretical framework for analyzing two-body nonleptonic
meson decays, based on the factorization of short-distance (long-distance)
dynamics into Wilson coefficients (hadronic matrix elements of four-fermion
operators). The parametrization of hadronic matrix elements in terms of several
nonperturbative quantities is demonstrated for the decays,
denoting a pseudoscalar meson. We consider the evolution of Wilson coefficients
with energy release in individual decay modes, and the Glauber strong phase
associated with the pion in nonfactorizable annihilation amplitudes, that is
attributed to the unique role of the pion as a Nambu-Goldstone boson and a
quark-anti-quark bound state simultaneously. The above inputs improve the
global fit to the branching ratios involving the meson, and resolves
the long-standing puzzle from the and
branching ratios, respectively. Combining short-distance dynamics associated
with penguin operators and the hadronic parameters determined from the global
fit to branching ratios, we predict direct CP asymmetries, to which the quark
loops and the scalar penguin annihilation give dominant contributions. In
particular, we predict , lower than the LHCb and CDF data.Comment: 17 pages, 3 figures, matches published versio
Branching ratios and direct CP asymmetries in decays
We study the two-body hadronic decays, where () denotes a
pseudoscalar (vector) meson, in the factorization-assisted
topological-amplitude approach proposed in our previous work. This approach is
based on the factorization of short-distance and long-distance dynamics into
Wilson coefficients and hadronic matrix elements of four-fermion operators,
respectively, with the latter being parametrized in terms of several
nonperturbative quantities. We further take into account the -
mixing effect, which improves the global fit to the branching ratios involving
the and mesons. Combining short-distance dynamics associated
with penguin operators and the hadronic parameters determined from the global
fit to branching ratios, we predict direct asymmetries. In particular, the
direct asymmetries in the , , and decays are found to be of , which can be
observed at the LHCb or future Belle II experiment. We also predict the
asymmetry observables of some neutral meson decays.Comment: 16 pages, 2 figure
Observation of Ultrahigh Mobility Surface States in a Topological Crystalline Insulator by Infrared Spectroscopy
Topological crystalline insulators (TCIs) possess metallic surface states
protected by crystalline symmetry, which are a versatile platform for exploring
topological phenomena and potential applications. However, progress in this
field has been hindered by the challenge to probe optical and transport
properties of the surface states owing to the presence of bulk carriers. Here
we report infrared (IR) reflectance measurements of a TCI, (001) oriented
in zero and high magnetic fields. We demonstrate that the
far-IR conductivity is unexpectedly dominated by the surface states as a result
of their unique band structure and the consequent small IR penetration depth.
Moreover, our experiments yield a surface mobility of 40000 ,
which is one of the highest reported values in topological materials,
suggesting the viability of surface-dominated conduction in thin TCI crystals.
These findings pave the way for exploring many exotic transport and optical
phenomena and applications predicted for TCIs
Understanding thermal induced escape mechanism of optically levitated sphere in vacuum
The escape phenomenon, mainly caused by thermal effects, is known as an
obstacle to the further practical application of optical levitation system in
vacuum. Irregular photophoresis induced by thermal effects can act as an
amplifier of Brownian motion. Studies on this topic provide interpretation for
particle escaping phenomenon during the pressure decreasing process, as well as
valuable insights into the micro- and nanoscale thermal effects in optical trap
in vacuum. In this paper, we derive and test a dynamic model for the motion of
an optically levitated particle in a non-equilibrium state and demonstrate the
escaping mechanism of heated particles. The result of theoretical
investigations is consistent with experimental escape at 0.1mbar. This work
reveals and provides a theoretical basis for the stable operation of laser
levitated oscillator in high vacuum and pave the way for the practicability of
ultra-sensitive sensing devices
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