Medium effects in coherent pion photo- and electroproduction on He and C

Drechsel, D.; Tiator, L.; Kamalov, S.S.; Yang, Shin Nan

doi:10.1016/s0375-9474(99)00412-1

Cited by 39 publications

(67 citation statements)

References 46 publications

(67 reference statements)

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“…The amplitudes of the elementary reactions are then evaluated at W (E γ , q). Up to this point there is analogy to the much better studied coherent π 0 photoproduction off (mostly J = 0) nuclei [144,145,146,147]. In this case the spin-and isospin-independent components of the elementary amplitude from all nucleons must be coherently added.…”

Section: Coherent Production 321 Single η-Production Off 3 He and 7mentioning

confidence: 99%

“…However, with few exceptions, the typical cross sections are small and the experiments are demanding (in most cases coherent reactions are difficult to identify in the presence of much larger contributions from breakup reactions). Detailed studies are so far only available for π 0 mesons to investigate the in-medium behaviour of the ∆(1232) resonance (see e.g., [144,145]) and, in a completely different context, for the extraction of nuclear mass form factors [146,147,148].…”

Section: Production In γA Reactionsmentioning

confidence: 99%

“…The nucleon momentum p N is related in the factorization approximation [144] to the momentum transfer q to the nucleus (note that the expressions in reference [144] are formulated for the c.m. system while in [147,180] the laboratory frame has been used)…”

Section: Coherent Production 321 Single η-Production Off 3 He and 7mentioning

confidence: 99%

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Production of η and η′ mesons on nucleons and nuclei

Krusche¹,

Wilkin²

2015

Progress in Particle and Nuclear Physics

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The production of η and η mesons in photon-and hadron-induced reactions on free and quasifree nucleons and on nuclei is reviewed. The extensive database on γN → ηN , for both proton and neutron targets, is described in detail and its implications for the search for N resonances much heavier than the dominant S 11 (1535) discussed. Though less is currently known about the production of the η or of ηπ pairs, these also offer tantalizing prospects in the search for the missing isobars. The more limited data available on pion-induced production are still necessary ingredients in the partial wave analysis discussed.The production of the η-meson in pp and pn collisions shows once again the strong influence of the S 11 (1535) isobar, which is in contrast to the relatively weak behaviour seen near threshold for η production. This difference is reflected in the important final state interaction effects of the η in nuclei that may even lead to this meson being "bound" in some systems. The evidence for this is reviewed for both γA and pA collisions. The inclusive photoproduction of η, η , and ηπ pairs from nuclei provides further information regarding the production mechanism and the interaction of the η and η with nuclei and the ηπ pairs may even allow access to low mass ηA systems that are forbidden in direct single-meson photoproduction.

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Section: Coherent Production 321 Single η-Production Off 3 He and 7mentioning

confidence: 99%

Section: Production In γA Reactionsmentioning

confidence: 99%

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Production of η and η′ mesons on nucleons and nuclei

Krusche¹,

Wilkin²

2015

Progress in Particle and Nuclear Physics

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“…However, for the full theoretical description, the FSI between the π 0 and the nucleus have to be accounted for [19].…”

Section: Coherent π 0 Photoproduction and Experimental Setupmentioning

confidence: 99%

Neutron skin studies in heavy nuclei with coherent p0 photo-production

Bondy¹

2015

Proceedings of 53rd International Winter Meeting on Nuclear Physics — PoS(Bormio2015)

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The charge distribution of nuclei is known with very high accuracy, i.e. in electron scattering experiments, conversely, the mass distribution is experimentally less accessible and therefore less precisely known. An accurate determination of the neutron density distribution is of particular interest. Especially in nuclei with N » Z, a strong neutron skin is expected, since the excess neutrons are pushed outwards against surface tension by the Coulomb forces. With the precise experimental determination of the neutron skin thickness essential constraints for the nuclear equation of state (EOS) can be provided and thus allowing to draw conclusions on the size of neutron stars. The method of coherent π 0 photoproduction, A(γ, π 0 )A, provides a powerful tool to determine the mass distribution of various nuclei. In a novel experimental campaign carried out in 2012 within the A2 collaboration at the Mainz Microtron (MAMI), five nuclei have been measured: 58 Ni, 116,120,124 Sn, 208 Pb. The tin targets are of special interest because most of the systematic errors due to pion-nucleon interaction can be neglected, and they allow a precise investigation along an isotopic chain. First results of these studies will be discussed.

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“…Because of the complexity of the strong interaction in nuclear reactions, many phenomena may contribute, making the theoretical analyses difficult. For instance, recent experimental work [26] on γ + d → π 0 + X and γ + Ca → π 0 + X suggested a controversial role for the D 13 (1520) by an empirical property change of the resonance [25,27]. It is essential for any theoretical model to introduce as few parameters as possible.…”

Section: Introductionmentioning

confidence: 99%

A quark model framework for the study of nuclear medium effects

Zhao¹,

Al-Khalili²,

Johnson³

2004

J. Phys. G: Nucl. Part. Phys.

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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.

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Medium effects in coherent pion photo- and electroproduction on He and C

Cited by 39 publications

References 46 publications

Production of η and η′ mesons on nucleons and nuclei

Production of η and η′ mesons on nucleons and nuclei

Neutron skin studies in heavy nuclei with coherent p0 photo-production

A quark model framework for the study of nuclear medium effects

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