arXiv subjects

S. Simula

Publications and source records attributed to S. Simula.

206 records · Page 12Linked to original sources

arXiv1995

Radiative $πρ$ and $πω$ transition form factors in a light-front constituent quark model

The form factors of the $πρ$ and $πω$ radiative transitions are evaluated within a light-front constituent quark model, using for the first time the eigenfunctions of a light-front mass operator reproducing the meson mass spectrum and including phenomenological Dirac and Pauli quark form factors in the one-body electromagnetic current operator. The sensitivity of the transition form factors both to the meson wave functions and to the constituent quark form factors is illustrated. It is shown that the measurement of the $πρ$ and $πω$ radiative transitions could help in discriminating among various models of the meson structure.

nucl-th↗

arXiv1995

Charge form factor of $π$ and $K$ mesons

The charge form factor of $π$ and $K$ mesons is evaluated adopting a relativistic constituent quark model based on the light-front formalism. The relevance of the high-momentum components of the meson wave function, for values of the momentum transfer accessible to $CEBAF$ energies, is illustrated. The predictions for the elastic form factor of $π$ and $K$ mesons are compared with the results of different relativistic approaches, showing that the measurements of the pion and kaon form factors planned at $CEBAF$ could provide information for discriminating among various models of the meson structure.

nucl-th↗

arXiv1995

Nucleon and pion electromagnetic form factors in a light-front constituent quark model

Nucleon and pion electromagnetic form factors are evaluated in the spacelike region within a light-front constituent quark model, where eigenfunctions of a mass operator, reproducing a large set of hadron energy levels, are adopted and quark form factors are considered in the one-body current. The hadron form factors are sharply affected by the high momentum tail generated in the wave function by the one-gluon-exchange interaction. Useful information on the electromagnetic structure of light constituent quarks can be obtained from the comparison with nucleon and pion experimental data.

nucl-th↗

arXiv1995

Realistic Model of the Nucleon Spectral Function in Few- and Many- Nucleon Systems

By analysing the high momentum features of the nucleon momentum distribution in light and complex nuclei, it is argued that the basic two-nucleon configurations generating the structure of the nucleon Spectral Function at high values of the nucleon momentum and removal energy, can be properly described by a factorised ansatz for the nuclear wave function, which leads to a nucleon Spectral Function in the form of a convolution integral involving the momentum distributions describing the relative and center-of-mass motion of a correlated nucleon-nucleon pair embedded in the medium. The Spectral Functions of $^3He$ and infinite nuclear matter resulting from the convolution formula and from many-body calculations are compared, and a very good agreement in a wide range of values of nucleon momentum and removal energy is found. Applications of the model to the analysis of inclusive and exclusive processes are presented, illustrating those features of the cross section which are sensitive to that part of the Spectral Function which is governed by short-range and tensor nucleon-nucleon correlations.

nucl-th↗

arXiv1995

Electromagnetic form factors of the $ρ$ meson in a light-front constituent quark model

The electromagnetic form factors of the $ρ$ meson are evaluated adopting a relativistic constituent quark model based on the light-front formalism, and using a meson wave function with the high-momentum tail generated by the one-gluon-exchange interaction. The breakdown of the rotational covariance for the one-body component of the current operator is investigated and the sensitivity of the ratio of the $ρ$-meson form factors to the pion (charge) form factor to the spin-dependent component of the effective $q \bar{q}$ interaction is illustrated.

hep-ph↗

arXiv1994

Nucleon-Nucleon Correlations and Six-Quark Cluster Effects in Semi-Inclusive Deep Inelastic Lepton Scattering off Few-Nucleon Systems

Semi-inclusive deep inelastic lepton scattering off few-nucleon systems is investigated assuming that virtual boson absorption occurs on a hadronic cluster which can be either a two-nucleon correlated pair or a six-quark bag. In both cases the relevance of nuclear effects on forward and backward nucleon emissions is illustrated and the differences expected in the energy distribution of the emitted nucleons are analyzed both at x>1 and x<1.

nucl-th↗

arXiv1994

Hard Constituent Quarks and Electroweak Properties of Pseudoscalar Mesons

The high momentum components generated in the wave function of pseudoscalar mes* by the one-gluon-exchange interaction are investigated within a relativistic constituent quark model. Adopting the light-cone formalism, the sensitivity of the weak decay constant and the charge form factor to hard constituent quarks is illustrated.

nucl-th↗

arXiv1994

Nucleon-Nucleon Correlations and Final State Interaction in Inclusive Quasi-Elastic Electron Scattering off Nuclei at x>1

Inclusive quasi-elastic electron scattering off nuclei is investigated at high momentum transfer (Q^2>1 (GeV/c)^2) and x>1 adopting a consistent treatment of nucleon-nucleon correlations in initial and final states. It is shown that in case of light as well as complex nuclei the inclusive cross section at 1.3 2 it is governed by the rescattering of the outgoing off-mass-shell nucleon in the complex optical potential generated by the ground state of the residual (A-1)-nucleon system.

nucl-th↗