A quark model framework for the study of nuclear medium effects

Abstract

A quark-model framework for studying nuclear medium effects on nucleon resonances is described and applied here to pion photoproduction on the deuteron, which is the simplest composite nucleon system and serves as a first test case. Pion photoproduction on nuclei is discussed within a chiral constituent quark model in which the quark degrees of freedom are explicitly introduced through an effective chiral Lagrangian for the quark-pseudoscalar-meson coupling. The advantage of this model is that a complete set of nucleon resonances can be systematically included with a limited number of parameters. Also, the systematic description of the nucleon and its resonances at quark level allows us to self-consistently relate the nuclear medium's influence on the baryon properties to the intrinsic dynamic aspects of the baryons. As the simplest composite nucleus, the deuteron represents the first application of this effective theory for meson photoproduction on light nuclei. The influence of the medium on the transition operators for a free nucleon is investigated in the Delta resonance region. No evidence is found for a change of the Delta properties in the pion photoproduction reaction on the deuteron since the nuclear medium here involves just one other nucleon and the low binding energy implies low nuclear density. However, we show that the reaction mechanism is in principle sensitive to changes of Delta properties that would be produced by the denser nuclear medium of heavier nuclei through the modification of the quark model parameters.

arXiv commentRevtex, 8 pages, 4 figures

References in corpus (20)

• A unitary isobar model for pion photo- and electroproduction on the proton up to 1 GeV
• Meson-exchange Model for $\pi N$ scattering and $\gamma N->\pi N$ reaction
• Dynamical Study of the Delta Excitation in N(e,e' pi) Reactions
• Updated resonance photo-decay amplitudes to 2 GeV
• Study of Non-Strange Baryon Resonances with Meson Photoproduction
• Multipole analysis of pion photoproduction based on fixed t dispersion relations and unitarity
• Nucleon Resonance Transition Couplings to Vector Mesons
• Interaction of small size wave packet with hadron target
• Quark Model Study of The eta Photoproduction: Evidence for a New S11 Resonance?
• Self consistent propagation of hyperons and antikaons in nuclear matter based on relativistic chiral SU(3) dynamics
• Pion photoproduction on the nucleon in the quark model
• Coherent ${\pi }^0$ and $\eta$ Photoproduction on the Deuteron
• Medium Effects in Coherent Pion Photo- and Electroproduction on 4He and 12C
• In-medium broadening of nucleon resonances
• In-medium properties of the D13(1520) nucleon resonance
• Quark model approach to the $\eta$ meson electroproduction on the proton
• In-medium modifications of the S11(1535) resonance and eta photoproduction
• Coherent π^\circ photoproduction from ^4He
• Two-body Mechanisms in Pion Photoproduction on the Trinucleon
• The P_33(1232) resonance contribution into the amplitudes M_{1+}^{3/2},E_{1+}^{3/2},S_{1+}^{3/2} from an analysis of the p(e,e'p)π^0 data at Q^2 = 2.8, 3.2, and 4 (GeV/c)^2 within dispersion relation approach