549 research outputs found
Study of f_0(980) and f_0(1500) from B_s \to f_0(980)\pi, f_0(1500)\pi Decays
In this paper, we analyze the scalar mesons and from
the decays within Perturbative
QCD approach. From the leading order calculations, we find that (a) in the
allowed mixing angle ranges, the branching ratio of is about , which is smaller than
that of (the difference is a few times even one
order); (b) the decay is better to distinguish
between the lowest lying state or the first excited state for ,
because the branching ratios for two scenarios have about one-order difference
in most of the mixing angle ranges; and (c) the direct CP asymmetries of for two scenarios also exists great difference. In
scenario II, the variation range of the value according to the mixing angle is very small, except for
the values corresponding to the mixing angles being near or
, while the variation range of in scenario I is very large. Compared with the future data for
the decay , it is ease to determine the nature
of the scalar meson .Comment: 16 pages, 3 figures, Revte
Revisiting the B {\to} {\pi} {\rho}, {\pi} {\omega} Decays in the Perturbative QCD Approach Beyond the Leading Order
We calculate the branching ratios and CP asymmetries of the ,
decays in the perturbative QCD factorization approach up to the
next-to-leading-order contributions. We find that the next-to-leading-order
contributions can interfere with the leading-order part constructively or
destructively for different decay modes. Our numerical results have a much
better agreement with current available data than previous leading-order
calculations, e.g., the next-to-leading-order corrections enhance the
branching ratios by a factor 2.5, which is helpful
to narrow the gaps between theoretic predictions and experimental data. We also
update the direct CP-violation parameters, the mixing-induced CP-violation
parameters of these modes, which show a better agreement with experimental data
than many of the other approaches.Comment: 23 pages, 4 figures, 4 table
Muon Anomalous Magnetic Moment and Lepton Flavor Violation
A non-universal interaction, which involves only the third family leptons
induces lepton flavor violating couplings and contributes to the anomalous
magnetic moment of muon. In this paper, we study the effects of non-universal
interaction on muon (g-2) and rare decay by using an
effective lagrangian technique, and a phenomenological model where
couples only to the third family lepton. We find that the deviation
from the theory can be explained and the induced rate
could be very close to the current experimental limit. In the model,
has to be lighter than 2.6 TeV.Comment: references added, the version to appear in PR
Novel Collective Effects in Integrated Photonics
Superradiance, the enhanced collective emission of energy from a coherent
ensemble of quantum systems, has been typically studied in atomic ensembles. In
this work we study theoretically the enhanced emission of energy from coherent
ensembles of harmonic oscillators. We show that it should be possible to
observe harmonic oscillator superradiance for the first time in waveguide
arrays in integrated photonics. Furthermore, we describe how pairwise
correlations within the ensemble can be measured with this architecture. These
pairwise correlations are an integral part of the phenomenon of superradiance
and have never been observed in experiments to date.Comment: 7 pages, 3 figure
The 3-3-1 model with S_4 flavor symmetry
We construct a 3-3-1 model based on family symmetry S_4 responsible for the
neutrino and quark masses. The tribimaximal neutrino mixing and the diagonal
quark mixing have been obtained. The new lepton charge \mathcal{L} related to
the ordinary lepton charge L and a SU(3) charge by L=2/\sqrt{3} T_8+\mathcal{L}
and the lepton parity P_l=(-)^L known as a residual symmetry of L have been
introduced which provide insights in this kind of model. The expected vacuum
alignments resulting in potential minimization can origin from appropriate
violation terms of S_4 and \mathcal{L}. The smallness of seesaw contributions
can be explained from the existence of such terms too. If P_l is not broken by
the vacuum values of the scalar fields, there is no mixing between the exotic
and the ordinary quarks at the tree level.Comment: 20 pages, revised versio
An assessment of the resolution limitation due to radiation-damage in x-ray diffraction microscopy
X-ray diffraction microscopy (XDM) is a new form of x-ray imaging that is
being practiced at several third-generation synchrotron-radiation x-ray
facilities. Although only five years have elapsed since the technique was first
introduced, it has made rapid progress in demonstrating high-resolution
threedimensional imaging and promises few-nm resolution with much larger
samples than can be imaged in the transmission electron microscope. Both life-
and materials-science applications of XDM are intended, and it is expected that
the principal limitation to resolution will be radiation damage for life
science and the coherent power of available x-ray sources for material science.
In this paper we address the question of the role of radiation damage. We use a
statistical analysis based on the so-called "dose fractionation theorem" of
Hegerl and Hoppe to calculate the dose needed to make an image of a lifescience
sample by XDM with a given resolution. We conclude that the needed dose scales
with the inverse fourth power of the resolution and present experimental
evidence to support this finding. To determine the maximum tolerable dose we
have assembled a number of data taken from the literature plus some
measurements of our own which cover ranges of resolution that are not well
covered by reports in the literature. The tentative conclusion of this study is
that XDM should be able to image frozen-hydrated protein samples at a
resolution of about 10 nm with "Rose-criterion" image quality.Comment: 9 pages, 4 figure
The corrosion of chromium based coatings for packaging steel
Chromium/chromium oxide based coatings, cathodically electrodeposited from either Cr (VI) or Cr (III) containing electrolytes are compared with respect to their ability to resist the corrosion driven delamination of an adherent polymer overcoat. Cathodic disbondment rates are determined using an in-situ scanning Kelvin probe technique. Anodic disbondment (filiform corrosion, FFC) rates are determined optically. The Cr (VI) derived coatings were fully resistant to corrosion driven disbondment. The Cr (III) derived coatings exhibited measurable rates of both FFC and cathodic disbondment. Disbondment kinetics are explained in relation to coating morphology, porosity and chemical composition determined using a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM) and xray photoelectron spectroscopy (XPS)
B_c meson rare decays in the light-cone quark model
We investigate the rare decays
and in the framework of the
light-cone quark model (LCQM). The transition form factors are calculated in
the space-like region and then analytically continued to the time-like region
via exponential parametrization. The branching ratios and longitudinal lepton
polarization asymmetries (LPAs) for the two decays are given and compared with
each other. The results are helpful to investigating the structure of
meson and to testing the unitarity of CKM quark mixing matrix. All these
results can be tested in the future experiments at the LHC.Comment: 9 pages, 11 figures, version accepted for publication in EPJ
Solvothermal synthesis of SnO2/graphene nanocomposites for supercapacitor application
A facile solvent-based synthesis route based on the oxidation–reduction reaction between graphene oxide (GO) and SnCl2·2H2O has been developed to synthesize SnO2/graphene (SnO2/G) nanocomposites. The reduction of GO and the in situ formation of SnO2 nanoparticles were achieved in one step. Characterization by X-ray diffraction (XRD), ultraviolet-visible (UV–vis) absorption spectroscopy, Raman spectroscopy, and field emission scanning electron microscopy (FESEM) confirmed the feasibility of using the solvothermally treated reaction system to simultaneously reduce GO and form SnO2 nanoparticles with an average particle size of 10 nm. The electrochemical performance of SnO2/graphene showed an excellent specific capacitance of 363.3 F/g, which was five-fold higher than that of the as-synthesized graphene (68.4 F/g). The contributing factors were the synergistic effects of the excellent conductivity of graphene and the nanosized SnO2 particles
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