Light quark mass ratio from Dalitz plot of η→π+π−π0\eta \to \pi^+\pi^-\pi^0 decay

High statistics Dalitz-plot distribution of $\eta \to \pi^+\pi^-\pi^0$ decay obtained recently by KLOE collaboration \cite{kloe} is fitted to the results of corresponding theoretical calculations in Chiral Perturbation Theory (ChPT) with unitarity corrections taken into account. The quark mass ratio $Q = \sqrt{(m^2_s - (m_d + m_u)^2/4)/(m^2_d - m^2_u)}$ can be otained from this analysis. We get $Q= 22.8\pm 0.4$ which differs from the value $Q_{DT} = 24.2$ that follows from Dashen's theorem and agrees with recently calculated electromagnetic kaon mass difference.Comment: 2 pages, no figure

Once more on electromagnetic form factors of nucleons in extended vector meson dominance model

Extended vector meson dominance model, that allows to describe the electromagnetic form factors of nucleons obeying the asymptotic quark counting rule prescriptions and contains the minimal number of free parameters, is presented. We get a reasonable fit of form factors over experimentally available space-like region of momentum transfer and get also reasonable results in the time-like region.Comment: 7 pages, 2 figure

Constraints on the relativistic mean field of Δ\Delta-isobar in nuclear matter

The effects of the presence of $\Delta$-isobars in nuclear matter are studied in the framework of relativistic mean-field theory. The existence of stable nuclei at saturation density imposes constraints on the $\Delta$-isobar self-energy and thereby on the mean-field coupling constants of the scalar and vector mesons with $\Delta$-isobars. The range of possible values for the scalar and vector coupling constants of $\Delta$-isobars with respect to the nucleon coupling is investigated and compared to recent predictions of QCD sum-rule calculations.Comment: 8 pages, Latex using Elsevier style, 2 PS figures, minor changes in revised versio