125 research outputs found
rho0 Production in Cu+Cu Collisions at 200 and 62.4 GeV in STAR
The results on rho(770)0 production in Cu+Cu collisions at 200 and 62.4 GeV
in STAR are presented. The rho0 is measured via its hadronic decay channel and
used as a sensitive tool to examine the collision dynamics in the hadronic
medium.Comment: 4 pages, 6 figures, to appear at the proceedings of the 21st
International Conference on Ultrarelativistic Nucleus-Nucleus Collisions,
QM2009, March 30 - April 4, Knoxville, T
Two Particle States and the -matrix Elements in Multi-channel Scattering
Using a quantum mechanical model, the exact energy eigenstates for
two-particle two-channel scattering are studied in a cubic box with periodic
boundary conditions in all three directions. A relation between the exact
energy eigenvalue in the box and the two-channel -matrix elements in the
continuum is obtained. This result can be viewed as a generalization of the
well-known L\"uscher's formula which establishes a similar relation in elastic
scattering.Comment: 18 pages, no figures. minor changes compared with previous versio
Multilevel Modeling of Interval-Contingent Data In Neuropsychology Research Using the \u3ci\u3eImerTest\u3c/i\u3e Package In R
Intensive longitudinal research designs are becoming more common in the field of neuropsychology. They are a powerful approach to studying development and change in naturally occurring phenomena. However, to fully capitalize on the wealth of data yielded by these designs, researchers have to understand the nature of multilevel data structures. The purpose of the present article is to describe some of the basic concepts and techniques involved in modeling multilevel data structures. In addition, this article serves as a step-by-step tutorial to demonstrate how neuropsychologists can implement basic multilevel modeling techniques with real data and the R package, lmerTest. R may be an ideal option for some empirical scientists, applied statisticians, and clinicians, because it is a free and open-source programming language for statistical computing and graphics that offers a flexible and powerful set of tools for analyzing data. All data and code described in the present article have been made publicly available
Decay and Scattering
Using chiral low energy theorems and elastic unitarity assumption, the
decay is investigated. The vector and scalar form
factors are calculated. It is found that the spectrum is dominated by
the resonance. By measuring the forward-backward asymmetry, it is shown
that the S wave phase shift can be determined near the
resonance region. The calculated branching ratio and resonance parameters are
in good agreement with experiments.Comment: 15 pages, Tex, 6 included figure
Pion-Kaon Scattering near the Threshold in Chiral SU(2) Perturbation Theory
In the context of chiral SU(2) perturbation theory, pion-kaon scattering is
analysed near the threshold to fourth chiral order. The scattering amplitude is
calculated both in the relativistic framework and by using an approach similar
to heavy baryon chiral perturbation theory. Both methods lead to equivalent
results. We obtain relations between threshold parameters, valid to fourth
chiral order, where all those combinations of low-energy constants which are
not associated with chiral-symmetry breaking terms drop out. The remaining
low-energy constants can be estimated using chiral SU(3) symmetry.
Unfortunately, the experimental information is not precise enough to test our
low-energy theorems.Comment: 38 pages, 5 figures, PhD Thesis, references adde
Lattice study on kaon pion scattering length in the channel
Using the tadpole improved Wilson quark action on small, coarse and
anisotropic lattices, scattering length in the channel is
calculated within quenched approximation. The results are extrapolated towards
the chiral and physical kaon mass region. Finite volume and finite lattice
spacing errors are also analyzed and a result in the infinite volume and
continuum limit is obtained. Our result is compared with the results obtained
using Roy equations, Chiral Perturbation Theory, dispersion relations and the
experimental data.Comment: Latex file typeset with elsart.cls, 9 pages, 3 figure
Genetic and environmental influences on fruit and vegetable consumption and depression in older adults
Background: Prior work suggests that higher fruit and vegetable consumption may protect against depression in older adults. Better understanding of the influence of genetic and environmental factors on fruit and vegetable intakes may lead to the design of more effective dietary strategies to increase intakes. In turn this may reduce the occurrence of depression in older adults. Objectives: The primary aim of this study is to estimate the genetic and environmental influences on the consumption of fruit and vegetables in older adults. The secondary aim is an exploratory analysis into possible shared genetic influences on fruit and vegetable intakes and depression. Methods: Analysis of observational data from 374 twins (67.1% female; 208 monozygotic (MZ); 166 dizygotic (DZ)) aged ≥ 65 years drawn from the Older Australian Twins Study. Dietary data were obtained using a validated food frequency questionnaire and depressive symptoms were measured using the 15-item short form Geriatric Depression Scale. The contribution of genetic and environmental influences on fruit and vegetable intake were estimated by comparing MZ and DZ twin intakes using structural equation modelling. A tri-variate twin model was used to estimate the genetic and environmental correlation between total fruit and vegetable intakes and depression. Results: In this study, vegetable intake was moderately influenced by genetics (0.39 95%CI 0.22, 0.54). Heritability was highest for brassica vegetables (0.40 95%CI 0.24, 0.54). Overall fruit intake was not significantly heritable. No significant genetic correlations were detected between fruit and vegetable intake and depressive symptoms. Conclusions: Vegetable consumption, particularly bitter tasting brassica vegetables, was significantly influenced by genetics, although environmental influences were also apparent. Consumption of fruit was only influenced by the environment, with no genetic influence detected, suggesting strategies targeting the food environment may be particularly effective for encouraging fruit consumption
Studying Kaon-pion S-wave scattering in K-matrix formalism
We generalize our previous work on \pi\pi scattering to K\pi scattering, and
re-analyze the experiment data of K\pi scattering below 1.6 GeV. Without any
free parameter, we explain K\pi I=3/2 S-wave phase shift very well by using
t-channel rho and u-channel K^* meson exchange. With the t-channel and
u-channel meson exchange fixed as the background term, we fit the K\pi I=1/2
S-wave data of the LASS experiment quite well by introducing one or two
s-channel resonances. It is found that there is only one s-channel resonance
between K\pi threshold and 1.6 GeV, i.e., K_0^*(1430) with a mass around
1438~1486 MeV and a width about 346 MeV, while the t-channel rho exchange gives
a pole at (450-480i) MeV for the amplitude.Comment: REVTeX4 file, 11 pages and 3 figure
A low-lying scalar meson nonet in a unitarized meson model
A unitarized nonrelativistic meson model which is successful for the
description of the heavy and light vector and pseudoscalar mesons yields, in
its extension to the scalar mesons but for the same model parameters, a
complete nonet below 1 GeV. In the unitarization scheme, real and virtual
meson-meson decay channels are coupled to the quark-antiquark confinement
channels. The flavor-dependent harmonic-oscillator confining potential itself
has bound states epsilon(1.3 GeV), S(1.5 GeV), delta(1.3 GeV), kappa(1.4 GeV),
similar to the results of other bound-state qqbar models. However, the full
coupled-channel equations show poles at epsilon(0.5 GeV), S(0.99 GeV),
delta(0.97 GeV), kappa(0.73 GeV). Not only can these pole positions be
calculated in our model, but also cross sections and phase shifts in the
meson-scattering channels, which are in reasonable agreement with the available
data for pion-pion, eta-pion and Kaon-pion in S-wave scattering.Comment: A slightly revised version of Zeitschrift fuer Physik C30, 615 (1986
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