Model for the Quasifree Polarization-Transfer Measurements in the (p,n) reaction at 495 MeV

The recent (p,n) polarization transfer experiments at LAMPF are explained in terms of a dropping rho-meson mass in the medium.Comment: 12 pages of text (LATEX), 4 figures (not included, available from the authors). February 199

Meson exchange model for pseudoscalar meson-meson scattering

A dynamical model for pseudoscalar-pseudoscalar meson scattering based on meson exchange, suitable for use in a variety of low- and intermediate-energy mesonic interactions, has been constructed and applied to ππ and kπ scattering with good quantitative results. The model includes both s- and t-channel exchange, and is found to require pseudoscalar-pseudoscalar coupling to a scalar octet to fit the high energy s-wave phases in the I = 0 ππ channel and in the channel. Coupling of the ππ and KK̄ channels is found to play a crucial role in explaining the S∗(975) resonanc

On the nature of the residual meson-meson interaction from simulations with a QED2+1{}_{2+1} model

A potential between mesons is extracted from 4-point functions within lattice gauge theory taking 2+1 dimensional QED as an example. This theory possesses confinement and dynamical fermions. The resulting meson-meson potential has a short-ranged hard repulsive core and the expected dipole-dipole forces lead to attraction at intermediate distances. Sea quarks lead to a softer form of the total potential.Comment: 4 pages, uuencoded tar-compressed postscript file, contribution to Lattice'9

On the Coupling of the η\eta Meson to the Nucleon

The pseudoscalar and pseudovector $\eta N$ coupling constants are calculated from an effective vertex associated with the $a_0(980)\pi N$ triangle diagram. The predicted values are in agreement with the ones concluded from fitting $\eta$ photoproduction amplitudes. In this context we stress the importance of the properties of the scalar meson octet for $\eta$ meson physics.Comment: 11 pages LATEX and 2 postscript figures included in a self-extracting uufile type archiv

Baryon-Baryon Potentials on the Lattice

The interaction of spatially extended heavy baryons is investigated in the framework of lattice QCD with dynamical quarks. It is shown that the expected dipole forces have a very short range and that the baryon-antibaryon interaction is more attractive than the baryon-baryon interaction. Sea quarks play a minor important role.Comment: 8 pages, uuencoded postscript file; Physics Letters B, in pres

Short range correlations in the pion s-wave self-energy of pionic atoms

We evaluate the contribution of second order terms to the pion-nucleus s-wave optical potential of pionic atoms generated by short range nuclear correlation. The corrections are sizeable because they involve the isoscalar s-wave πN amplitude for half off-shell situations where the amplitude is considerably larger than the on-shell one. In addition, the s-wave optical potential is reanalyzed by looking at all the different conventional contributions together lowest order, Pauli corrected rescattering term, second order absorptive effects, terms from the interaction of pions with the virtual pion cloud (chiral corrections) and correlation effects. Different off-shell extrapolations for the πN amplitude are used and it is found that, although some individual terms are sensitive to the extrapolation, the sum of them is rather insensitive. The results are compared with empirical values from best fits to the data and are found to be compatible, within theoretical and empirical uncertainties. The results do not rule out further contributions but they put stringent constraints on their strength

Meson-meson correlations in baryon-baryon and antibaryon-baryon interactions

Recent work of the J\"ulich group about the role of meson-meson correlations in baryon-baryon and antibaryon-baryon interactions is reviewed.Comment: Lecture given at the Erice School 1995, TEX, 10 pages, 15 figure