Model For Electroproduction Research Articles

Effects of final-state interaction in lepton-pair production in proton-proton collisions, and in the massive quark model for electroproduction

We point out that analysis of a particular structure function for massive muon-pair production in proton-proton collisions may be capable of signaling the diffractive corrections which are expected, in the parton model, to be present in addition to the "bare" Drell-Yan term. A similar analysis of single-particle semi-inclusive electroproduction in the massive quark model suggests that the azimuthal angle dependence should be suppressed at most by logarithms of ${q}^{2}$, at variance with the behavior expected in the parton model. This investigation reveals the importance of a particular assumption which is necessary in the derivation of the parton-model result.

Connection between the electromagnetic form factors of hadrons and sidewise dispersion relations

It is shown that the analyticity of electromagnetic form factors in the invariant hadron masses and the unitarity condition lead to a system of linear relations between various form factors. The construction of such a system is a general way of expressing the hardly measured inelastic form factors in terms of the elastic ones. In the concrete case this system for the form factors: F π ( k 2), F ωπγ(k 2), F ϱπγ(k 2) and F N ∗ (1470)γ (k 2) , allowing one to express them in terms of the nucleon form factors, was obtained by sidewise dispersion relations in elastic unitarity. The obtained meson form factors behave like k −2 for large k 2. The pion radius 〈 r π 〉 is equal to 〈 r π〉 = 0.68 fm . The system of equations leads to a ratio [(1 (1 + μ p) p E/ G p M] 2 2 which deviates from scaling in the region k 2 ≈ 4.2 GeV 2 but not at k 2 = 0 and k 2 ⪢ 2 GeV 2 In the framework of the Chew-Goldberger-Low-Nambu approach, a model of electroproduction for the saturation of the sidewise dispersion relation has been chosen so that besides the Born terms we take into account the exchange of ω,ϱ mesons in the t-channel as well as the magnetic dipole M 1+ 3 2 ofd electric quadrupole E 1+ 3 2 of the Δ 33 resonance in the u-channel.

Electroproduction of ω-mesons as a test of the ϱωπ-vertex

A simple model for electroproduction of ω-mesons is presented. The non-diffractive part is described by elementary OPE without corrections, combined with vector-meson dominance. For the diffractive production amplitudes we assume helicity conservation in the direct channel. We discuss the differential cross section and the spin-density matrix of the ω-mesons, particularly emphasizing the dependence on the mass of the virtual photon and the possibility to test the mass-dependence of the ϱωπ coupling constant.

Simple Parton Dual-Resonance Model for Electroproduction and Lepton-Pair Annihilation Processes with the Incorporation of Final-State Interaction

Simple Parton Dual-Resonance Model for Electroproduction and Lepton-Pair Annihilation Processes with the Incorporation of Final-State Interaction

A model for electroproduction and photoproduction of pions near theN*(1236) resonance*(1236) resonance

A model for electroproduction and photoproduction of pions near theN*(1236) resonance*(1236) resonance

When Will Electroproduction and Photoproduction Show Diffractive Features?

A simple interpretation is given to the diffraction model for electroproduction and photoproduction, on the basis of which we venture to provide answers to the question: When will electroproduction and photoproduction data show diffractive features? Conjectures are also made regarding the region of validity for Sakurai's results on electroproduction.

Relativistic Model for Electroproduction of Nucleon Resonances. II

Relativistic Model for Electroproduction of Nucleon Resonances. II

Photo-, electro-, and weak single-pion production in the (3,3) resonance region

We give a unified account of single-pion photo-, electro-, and weak production. The emphases of the paper are fourfold: (1) We give a detailed kinematic discussion of single-pion electro- and weak-production; (2) we develop a dynamical model for electroproduction and weak production in the (3,3) resonance region, based on the CGLN model for photoproduction; (3) we systematically discuss the partially-conserved axail-vector current (PCAC) and current-algebra constraints which relate the single-pion electro- and weak-production matrix elements to the matrix elements for other processes; (4) we compare our model with experiment.

Relativistic Model for Electroproduction of Nucleon Resonances

We have made a simple model to obtain some estimates of the inelastic form factors for electron excitation of the nucleon resonances. The model is covariant and gauge invariant, and satisfies all the general requirements of the theory. It relies heavily on the lead of previous theoretical work on the form factor for the ${\frac{3}{2}}^{+}$, $\frac{3}{2}$ (1238-MeV) level. The basic idea is to take from experiment the knowledge of which nucleon states are resonant. We then look at single-pion electroproduction and project out the relevant multipoles from a covariant, gauge-invariant set of graphs which are thought to play an important role as an excitation mechanism. The multipoles are then multiplied by a final-state enhancement factor which provides a resonance mechanism. We give some theoretical justification for this procedure. If just the electron is detected, one measures the virtual-photon width for formation of the resonance, and our result contains the possibility that the resonance can decay into other channels than just $\ensuremath{\pi}+N$. We calculate only the inelastic form factors. The individual contributions of the resonance levels are normalized to photoabsorption, where such data exist. We keep $\ensuremath{\pi}$, $\ensuremath{\omega}$, and $N$ exchange as an excitation mechanism, and treat the over-all contribution of the $\ensuremath{\omega}$ exchange as a single parameter, with which we are able to fit all the existing inelastic-electron-scattering data. We actually find two equally acceptable fits with quite different properties. The $\ensuremath{\omega}$-nucleon coupling constant we get from this analysis is in reasonable agreement with other determinations of this quantity. Form factors for all the nucleon levels up through 2650 MeV are presented out to momentum transfers of interest in the SLAC experiments.