2,380 research outputs found
Are autumn foliage colors red signals to aphids?
http://creativecommons.org/licenses/by/2.0
Chiral dynamics in the gamma p --> pi^0 eta p and gamma p --> pi^0 K^0 Sigma^+ reactions
Using a chiral unitary approach for meson-baryon scattering in the
strangeness zero sector, where the resonance is dynamically
generated, we study the reactions and at photon energies at which the final states are produced
close to threshold. Among several reaction mechanisms, we find the most
important is the excitation of the state which subsequently
decays into a pseudoscalar meson and a baryon belonging to the
decuplet. Hence, the reaction provides useful information with which to test
current theories of the dynamical generation of the low-lying states.
The first reaction is shown to lead to sizable cross sections and the
resonance shape is seen clearly in the invariant mass
distribution. The same dynamical model is shown to lead to much smaller cross
sections at low energies in the second reaction. Predictions are made for cross
sections and invariant mass distributions which can be compared with
forthcoming experiments at ELSA.Comment: 22 pages, 22 figure
Chiral Dynamics and S-wave Contributions in Semileptonic B decays
The flavor-changing neutral current process is beneficial to
testing the standard model and hunting for new physics scenarios. In exclusive
decay modes like , the S-wave effects may not be
negligible and thus have to be reliably estimated. Using the scalar form
factors derived from dispersion relations in two channels and matched to Chiral
Perturbation Theory, we investigate the S-wave contributions in , with the invariant mass lying in the vicinity of the
mass of , and the with .
We find that the S-wave will modify differential decay widths by about 10% in
the process of and about 5% in . A forward-backward asymmetry for the charged kaon in the final state
arises from the interference between the S-wave and P-wave contributions. The
measurement of this asymmetry offers a new way to determine the variation of
the S-wave phase versus the invariant mass.Comment: 26 pages, 10 figure
Radiative decay of the Delta(1700)
Electromagnetic properties provide information about the structure of
strongly interacting systems and allow for independent tests of hadronic
models. The radiative decay of the Delta(1700) is studied, which appears
dynamically generated in a coupled channel approach from the rescattering of
the (3/2^+) decuplet of baryons with the (0^-) octet of pseudoscalar mesons.
The radiative decay is predicted from the well-known couplings of the photon to
the mesons and hadrons which constitute this resonance in the dynamical
picture.Comment: 14 pages, 4 figure
Online Knowledge Sharing: Investigating the Community of Inquiry Framework and Its Effect on Knowledge Sharing Behavior in Online Learning Environments
The purpose of this study was to examine whether the CoI framework can predict self-reported knowledge sharing behaviors within graduate-level online courses. The overall goal was to determine if high levels of social, teaching, and cognitive presence can lead to increased knowledge distribution within online learning environments, leading to the co-construction of knowledge among learners. As part of the study, graduate students from the field of education were asked to complete a survey, which combined Swan et al.\u27s (2008) CoI survey instrument and Yu, Lu, & Liu\u27s (2010) knowledge sharing survey tool. The survey assessed students\u27 perceptions of social, teaching, and cognitive presence within their respective online courses, and also measured their knowledge sharing behavior within these same courses. The independent variables were totaled scores of social presence, teaching presence, and cognitive presence. The dependent variable was the totaled score of knowledge sharing behavior.
A standard multiple regression design was utilized to determine whether the independent variables (social presence, teaching presence, and cognitive presence) are predictors of the dependent variable (knowledge sharing behavior). Regression results indicated that an overall model with two independent variables - teaching presence and social presence - significantly predicts knowledge sharing behavior, R2 = .637, R2adj=.615, F(2, 33) = 29.001, p \u3c .001. Cognitive presence, however, was not shown to significantly contribute to this model. In line with existing theories - including social capital theory, the organization knowledge creation theory (OKCT), and self-determination theory - results suggest that the more social elements of the CoI framework might better motivate students to interact and share knowledge. On the other hand, cognitive presence, which is more closely tied to individual learning outcomes, plays a smaller role in motivating students to participate and share knowledge within online learning environments
Heavy quark free energies and screening at finite temperature and density
We study the free energies of heavy quarks calculated from Polyakov loop
correlation functions in full 2-flavour QCD using the p4-improved staggered
fermion action. A small but finite Baryon number density is included via Taylor
expansion of the fermion determinant in the Baryo-chemical potential mu. For
temperatures above Tc we extract Debye screening masses from the large distance
behaviour of the free energies and compare their mu-dependence to perturbative
results.Comment: 6 pages, Presented at 23rd International Symposium on Lattice Field
Theory (Lattice 2005), Trinity College, Dublin, Ireland, 25-30 Jul 200
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