Decays of Non-Strange Positive Parity Excited Baryons in the 1/Nc Expansion

The decays of non-strange positive parity excited baryons via emission of a pseudo-scalar meson are studied in the framework of the 1/Nc expansion to order 1/Nc. In particular, the pionic decays of the l=0 Roper baryons and of the l=2 baryons in the mass interval 1680-1950 MeV are analyzed using the available partial decay widths. Decay widths by emission of an eta meson are shown to be suppressed by a factor 1/Nc^2 with respect to the pionic ones.Comment: 16 pages, 8 table

Production of scalar KKˉK\bar K molecules in ϕ\phi radiative decays

The potentialities of the production of the scalar $K\bar K$ molecules in the $\phi$ radiative decays are considered beyond the narrow resonance width approximation. It is shown that $BR(\phi\rightarrow\gamma f_0(a_0)\rightarrow\gamma\pi\pi(\pi\eta))\approx (1\div 2)\times 10^{-5}\ ,\BR(\phi\rightarrow\gamma (f_0+a_0)\rightarrow\gamma K^+K^-)\alt 10^{-6}$and$BR(\phi\rightarrow\gamma (f_0+a_0) \to \gamma K^0\bar K^0)\alt 10^{-8}$. The mass spectra in the$\pi\pi\ ,\ \pi\eta\ ,\ K^+K^-\ ,\ K^0\bar K^0$channels are calculated. The imaginary part of the amplitude$\phi\rightarrow\gamma f_0(a_0)$is calculated analytically. It is obtained the phase of the scalar resonance production amplitude that causes the interference patterns in the reaction$e^+e^-\rightarrow\gamma \pi^+\pi^-$in the$\phi$ meson mass region.Comment: 19 pages, revtex, 4 eps files of figure

Off-Shell Scattering Amplitudes for WW Scattering and the Role of the Photon Pole

We derive analytic expressions for high energy $2 \to 2$ off-shell scattering amplitudes of weak vector bosons. They are obtained from six fermion final states in processes of the type $e^+ e^- \to \bar\nu_e + (WW) + \nu_e \to \bar\nu_e + (l\nu)(l\nu) + \nu_e$. As an application we reconsider the unitarity bounds on the Higgs mass. Particular attention is given to the role of the photon exchange which has not been considered in earlier investigations; we find that the photon weakens the bound of the Higgs mass.Comment: 16 pages, 8 figure