Pionic Degrees of Freedom in Atomic Nuclei and Quasielastic Knockout of Pions by High-Energy Electrons

The nonlinear model of pionic condensate in nuclei by G. Preparata can be efficiently verified by investigation of the quasielastic knockout process of pions out of nuclei by high energy electrons. First, a momentum distribution (MD) of the collective pions has a bright maximum at q=0.3 Gev.Second the excitation spectrum of a recoil nucleus is concentrated at low energies E lesser than 1MeV. The results for the pion knockout from mesonic clouds of individual nucleons are absolutely different. The latter results are presented both for pion and rho-meson clouds localized on nucleons.Comment: 13 pages, 3 figure

Bremsstrahlung of 350--450 MeV protons as a tool to study NNNN interaction off-shell

The $pp\to pp\gamma$ bremsstrahlung cross section is calculated within the method of coordinate space representation. It is shown that in the beam energy range of 350--450~MeV a deep attractive NN-potential with forbidden states (Moscow potential) and realistic meson exchange potentials (MEP) give rise to the cross sections that differ essentially in shape: the cross sections nearly coincide in the minima but differ by a factor of 5 approximately in the maxima. Therefore, the $pp\to pp\gamma$ reaction at energies $\sim$350--450~Mev can be used to study $NN$ interaction off-shell and to discriminate experimentally between MEP and Moscow potential.Comment: 5 pages, latex, 4 PS figures. Talk presented by Andrey Shirokov at the International Conference on Quark Lepton Nuclear Physics ``QULEN97'', May 20-23, 1997, Osaka, Japan; to be published in Nucl. Phys.

Quasi-elastic knockout of pions and kaons from nucleons by high-energy electrons and quark microscopy of "soft" meson degrees of freedom in the nucleon

Electro-production of pions and kaons at the kinematics of quasi-elastic knockout (which is well known in the physics of atomic nucleus and corresponds to the $t$-pole diagram) is proposed for obtaining their momentum distribution (MD) in various channels of virtual decay $N \to B+\pi$, $B=N$, $\Delta$, $N^*$, $N^{**}$, and $N \to Y+K$, $Y=\Lambda$, $\Sigma$. It is a powerful tool for investigation of a quark microscopic picture of the meson cloud in the nucleon. A model of scalar $q \bar{q}$ ($^3P_0$) fluctuation in the non-trivial QCD vacuum is used to calculate pion and kaon momentum distributions (MD) in these channels.Comment: 31 pages, 11 figures, submitted to Nucl.Phys.

Nucleon-nucleon wave function with short-range nodes and high-energy deuteron photodisintegration

We review a concept of the Moscow potential (MP) of the $NN$ interaction. On the basis of this concept we derive by quantum inversion optical partial potentials from the modern partial-wave analysis (PWA) data and deuteron properties. Point-form (PF) relativistic quantum mechanics (RQM) is applied to the two-body deuteron photodisintegration. Calculations of the cross-section angular distributions cover photon energies between 1.1 and 2.5 GeV. Good agreement between our theory and recent experimental data confirms the concept of deep attractive Moscow potential with forbidden $S$- and $P$-states.Comment: 31 pages, 9 figures. typos, extended formalism, review of the Moscow potential model adde

Microscopics of meson degrees of freedom in nucleons and mesons in nuclei - what can be seen in the process of quasielastic knockout of mesons by high-energy electrons

Developed earlier concept of quasielastic knock out of pions from nucleons by high-energy electrons is propounded as a tool for checking microscopical model ($^3P_0$ - fluctuation) for decay of N to different channels $\pi+B$ and Preparata model of nucleus structure.Comment: 6 pages, 5 figures, Talk given at 16 Baldin Symposium in June 200

Baryons, their interactions and the chiral symmetry of QCD

An implication of the spontaneous chiral symmetry breaking in QCD is that at low energy and resolution there appear quasiparticles - constituent quarks and Goldstone bosons. Thus, light and strange baryons should be considered as systems of three constituent quarks with confining interaction and a chiral interaction that is mediated by Goldstone bosons between the constituent quarks. We show how the flavor-spin structure and sign of the short-range part of the Goldstone boson exchange interaction reduces the $SU(6)_{FS}$ symmetry down to $SU(3)_F \times SU(2)_S$, induces hyperfine splittings and provides correct ordering of the lowest states with positive and negative parity. We present a unified description of light and strange baryon spectra calculated in a semirelativistic framework. It is demonstrated that the same short-range part of Goldstone boson exchange also induces strong short-range repulsion in $NN$ system when the latter is treated as $6Q$ system. Thus, all main ingredients of $NN$ interaction are implied by the chiral constituent quark model since the long- and intermediate-range attraction appears in the present framework due to pion and correlated two-pion exchanges between quarks belonging to different nucleons. We also find a very strong short-range repulsion in $\Lambda\Lambda$ system with $J^P=0^+$. It then suggests that the compact H-particle should not exist.Comment: 10 pages, Invited talk given at International Conference on Quark Lepton Nuclear Physics (QULEN97, May 20-23, 1997, Osaka, Japan

Phase equivalent potentials for three-body halos

We compare the properties of three-body systems obtained with two-body potentials with Pauli forbidden states and with the corresponding phase equivalent two-body potentials. In the first case the forbidden states are explicitly excluded in the calculation. Differences arise due to the off-shell properties of these on-shell equivalent potentials. We use the adiabatic hyperspherical method to formulate a practical prescription to exclude Pauli forbidden states in three-body calculations. Schematic as well as realistic potentials are used. Almost indistinguishable results are obtained.Comment: 18 pages, 6 figure

Quark model description of quasi-elastic pion knockout from the proton at JLAB

The interference term between s- and t-pole contributions to the p(e,e' pi+)n cross section is evaluated on the basis of the constituent quark model. It is shown that the contribution of baryon s-poles can be modeled by a nonlocal extension of the Kroll-Rudermann contact term. This contribution is in a destructive interference with the pion t-pole that is essential to improve the description of recent JLab data at the invariant mass W=1.95 GeV. Some predictions are made for a new JLab measurement at higher values W=2.1-2.3 GeV and Q2 centered at 1.6 and 2.45 GeV2/c2.Comment: 15 pages, 4 figures, to be published in Phys. Lett.