The underlying mixing of quark components of scalar mesons is probed in πK scattering within a generalized linear sigma model that contains two scalar meson nonets and two pseudoscalar meson nonets (a quark-antiquark and a four-quark). In the leading order of this model, all free parameters have been previously fixed using the mass spectra and several low-energy parameters known from experiment and consistent predictions have been made. As other predictions of the model, in the present work the isospins I= 1/2, 3/2 and J=0 projection of πK scattering amplitude (as well as phase shifts) are computed and compared with experiment. In the I=1/2 channel, it is shown that within the uncertainties of the model parameters a good agreement with experimental data up to an energy of about 1 GeV is obtained, whereas in the I=3/2 channel there is a better agreement with experiment which extends to about 1.4 GeV. The effect of final state interactions of πK in the I=1/2 channel is approximated by the K-matrix method and the poles of the unitarized scattering amplitude are found. It is shown that the model predicts a light and broad kappa resonance with a mass and decay width of 670-770 MeV and 640-750 MeV consistent with other prior works. Moreover, the scattering lengths in the I=1/2, 3/2 are also computed and shown to qualitatively agree with experiment. The overall predictions presented here further support previous findings that the scalar mesons below and above 1 GeV have substantial underlying mixings and that those below 1 GeV have dominant four-quark substructures while those above 1 GeV are closer to conventional P -wave quark-antiquark states.

In this article, the three-point QCD sum rules are used to compute the strong coupling constants of vertices containing the strange bottomed (charmed) mesons with the pion. The coupling constants are calculated when both the bottom (charm) and the pion states are off-shell. A comparison of the obtained results of the coupling constants with existing predictions is also made.

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Mass renormalization of the electron in configurations such as metallic hydride surfaces due to electromagnetic field fluctuations leads to mass enhancement of the electron, which is known as the heavy electron. The effective mass renormalization has substantial consequences in the theory of electromagnetic field interaction with matter (QED). One of the fascinating effects appears when an external photon interacts with the heavy electron. In this case, the wavelength of the scattered photon from the electron increases and the hard photon turns into a soft photon. In this paper, we present a novel mechanism to show how the heavy electron results in hard photon absorption.