892 research outputs found
G′ band in double- and triple-walled carbon nanotubes: A Raman study
Double- and triple-walled carbon nanotubes are studied in detail by laser energy-dependent Raman spectroscopy in order to get a deeper understanding about the second-order G[superscript '] band Raman process, general nanotube properties, such as electronic and vibrational properties, and the growth method itself. In this work, the inner nanotubes from the double- and triple-walled carbon nanotubes are produced through the encapsulation of fullerene peapods with high-temperature thermal treatments. We find that the spectral features of the G[superscript '] band, such as the intensity, frequency, linewidth, and line shape are highly sensitive to the annealing temperature variations. We also discuss the triple-peak structure of the G[superscript '] band observed in an individual triple-walled carbon nanotube taken at several laser energies connecting its Raman spectra with that for the G[superscript '] band spectra obtained for bundled triple-walled carbon nanotubes.National Science Foundation (U.S.) (Grant 1004147
A Review of Double-Walled and Triple-Walled Carbon Nanotube Synthesis and Applications
Double- and triple-walled carbon nanotubes (DWNTs and TWNTs) consist of coaxially-nested two and three single-walled carbon nanotubes (SWNTs). They act as the geometrical bridge between SWNTs and multi-walled carbon nanotubes (MWNTs), providing an ideal model for studying the coupling interactions between different shells in MWNTs. Within this context, this article comprehensively reviews various synthetic routes of DWNTs’ and TWNTs’ production, such as arc discharge, catalytic chemical vapor deposition and thermal annealing of pea pods (i.e., SWNTs encapsulating fullerenes). Their structural features, as well as promising applications and future perspectives are also discussed. Keywords: carbon nanotubes; double-walled carbon nanotubes; triple-walled carbon nanotubes; synthesis; catalytic chemical vapor deposition; arc discharge; fullerenes; pea pod
A New 5-Flavour LO Analysis and Parametrization of Parton Distributions in the Real Photon
New, radiatively generated, LO quark (u,d,s,c,b) and gluon densities in a
real, unpolarized photon are presented. We perform a global 3-parameter fit,
based on LO DGLAP evolution equations, to all available data for the structure
function F2^gamma(x,Q^2). We adopt a new theoretical approach called ACOT(chi),
originally introduced for the proton, to deal with the heavy-quark thresholds.
This defines our basic model (CJKL model), which gives a very good description
of the experimental data on F2^gamma(x,Q^2), for both Q^2 and x dependences.
For comparison we perform a standard fit using the Fixed Flavour-Number Scheme
(FFNS_CJKL model), updated with respect to the previous fits of this type. We
show the superiority of the CJKL fit over the FFNS_CJKL one and other LO fits
to the F2^gamma(x,Q^2) data. The CJKL model gives also the best description of
the LEP data on the Q^2 dependence of the F2^gamma, averaged over various
x-regions, and the F_2,c^gamma, which were not used directly in the fit.
Finally, a simple analytic parametrization of the resulting parton densities
obtained with the CJKL model is given.Comment: 43 pages, RevTeX4 using axodraw style, 3 tex and 12 postscript
figures, version submitted to Phys. Rev. D, small text changes, one reference
added, FORTRAN program available at http://www.fuw.edu.pl/~pjank/param.html
and at http://www-zeuthen.desy.de/~alorca/id4.htm
A Measurement of the Cross Section in Two-Photon Processes
We have measured the inclusive production cross section in a
two-photon collision at the TRISTAN collider. The mean of
the collider was 57.16 GeV and the integrated luminosity was 150 . The
differential cross section () was obtained in the
range between 1.6 and 6.6 GeV and compared with theoretical predictions, such
as those involving direct and resolved photon processes.Comment: 8 pages, Latex format (article), figures corrected, published in
Phys. Rev. D 50 (1994) 187
Low- and high-mass components of the photon distribution functions
The structure of the general solution of the inhomogeneous evolution
equations allows the separation of a photon structure function into
perturbative (``anomalous") and non-perturbative contributions. The former part
is fully calculable, and can be identified with the high-mass contributions to
the dispersion integral in the photon mass. Properly normalized ``state"
distributions can be defined, where the \gamma\to\qqbar splitting probability
is factored out. These state distributions are shown to be useful in the
description of the hadronic event properties, and necessary for a proper
eikonalization of jet cross sections. Convenient parametrizations are provided
both for the state and for the full anomalous parton distributions. The
non-perturbative parts of the parton distribution functions of the photon are
identified with the low-mass contributions to the dispersion integral. Their
normalizations, as well as the value of the scale at which the
perturbative parts vanish, are fixed by approximating the low-mass
contributions by a discrete, finite sum of vector mesons. The shapes of these
hadronic distributions are fitted to the available data on .
Parametrizations are provided for GeV and GeV, both in the
DIS and the factorization schemes. The full
parametrizations are extended towards virtual photons. Finally, the often-used
``FKP-plus-TPC/" solution for is commented upon.Comment: 33 pages, Latex, 6 Z-compressed and uuencoded figure
Measurement of azimuthal asymmetries in inclusive charged dipion production in annihilations at = 3.65 GeV
We present a measurement of the azimuthal asymmetries of two charged pions in
the inclusive process based on a data set of 62
at the center-of-mass energy GeV collected with
the BESIII detector. These asymmetries can be attributed to the Collins
fragmentation function. We observe a nonzero asymmetry, which increases with
increasing pion momentum. As our energy scale is close to that of the existing
semi-inclusive deep inelastic scattering experimental data, the measured
asymmetries are important inputs for the global analysis of extracting the
quark transversity distribution inside the nucleon and are valuable to explore
the energy evolution of the spin-dependent fragmentation function.Comment: 7 pages, 5 figure
Study of
We present an analysis of the decay based
on data collected by the BESIII experiment at the resonance. Using
a nearly background-free sample of 18262 events, we measure the branching
fraction . For GeV/ the partial branching fraction is
. A partial wave analysis shows that the dominant
component is accompanied by an \emph{S}-wave contribution accounting for
of the total rate and that other components are
negligible. The parameters of the resonance and of the
form factors based on the spectroscopic pole dominance predictions are also
measured. We also present a measurement of the helicity
basis form factors in a model-independent way.Comment: 17 pages, 6 figure
Study of and and
We study the decays of and to the final states
and based on a single
baryon tag method using data samples of
and events collected with
the BESIII detector at the BEPCII collider. The decays to
are observed for the first time. The
measured branching fractions of and
are in good agreement with, and much
more precise, than the previously published results. The angular parameters for
these decays are also measured for the first time. The measured angular decay
parameter for , , is found to be negative, different to the other
decay processes in this measurement. In addition, the "12\% rule" and isospin
symmetry in the and and
systems are tested.Comment: 11 pages, 7 figures. This version is consistent with paper published
in Phys.Lett. B770 (2017) 217-22
Measurement of the Cross Section between 600 and 900 MeV Using Initial State Radiation
We extract the cross section in the energy
range between 600 and 900 MeV, exploiting the method of initial state
radiation. A data set with an integrated luminosity of 2.93 fb taken at
a center-of-mass energy of 3.773 GeV with the BESIII detector at the BEPCII
collider is used. The cross section is measured with a systematic uncertainty
of 0.9%. We extract the pion form factor as well as the
contribution of the measured cross section to the leading order hadronic vacuum
polarization contribution to . We find this value to be
.Comment: 14 pages, 7 figures, accepted by PL
Measurements of absolute hadronic branching fractions of baryon
Using of collisions recorded at
with the BESIII detector, we report first measurements
of absolute hadronic branching fractions of Cabibbo-favored decays of the
baryon with a double-tag technique. A global least-square
fitter is utilized to improve the measured precision. Among the measurements
for twelve decay modes, the branching fraction for
is determined to be
, where the first uncertainty is statistical and the
second is systematic. In addition, the measurements of the branching fractions
of the other eleven Cabbibo-favored hadronic decay modes are significantly
improved
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