Are autumn foliage colors red signals to aphids?

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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 $N^*(1535)$ resonance is dynamically generated, we study the reactions $\gamma p \to \pi^0 \eta p$ and $\gamma p \to \pi^0 K^0 \Sigma^+$ 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 $\Delta^*(1700)$ state which subsequently decays into a pseudoscalar meson and a baryon belonging to the $\Delta(1232)$ decuplet. Hence, the reaction provides useful information with which to test current theories of the dynamical generation of the low-lying $3/2^-$ states. The first reaction is shown to lead to sizable cross sections and the $N^*(1535)$ resonance shape is seen clearly in the $\eta p$ 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 $b\to s l^+l^-$ is beneficial to testing the standard model and hunting for new physics scenarios. In exclusive decay modes like $B\to K^*(892)l^+l^-$, 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 $\bar B^0\to K^- \pi^+ l^+l^-$, with the $K\pi$ invariant mass lying in the vicinity of the mass of $K^*(892)$, and the $B_s\to K^- K^+ l^+l^-$ with $m_{KK}\sim m_{\phi}$. We find that the S-wave will modify differential decay widths by about 10% in the process of $\bar B^0\to K^- \pi^+ l^+l^-$ and about 5% in $B_s\to K^- K^+ l^+l^-$. 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 $K\pi$ 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