New calculations for incoherent eta photoproduction on nuclei including nonlocal and medium effects

Hedayati-Poor, M.; Sherif, H. S.

doi:10.1016/j.nuclphysa.2004.05.011

Cited by 3 publications

(2 citation statements)

References 23 publications

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“…The final-state interactions (FSI) of the mesons are taken into account either using optical potentials [10], the quantum molecular dynamics (QMD) model of Ref. [11], or the Boltzmann-Uehling-Uhlenbeck (BUU) transport model [12].…”

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η→γγDecay Width via the Primakoff Cross Section

et al. 2008

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Incoherentphotoproduction in nuclei is evaluated at forward angles within 4 to 9 GeV using a multiple scattering Monte Carlo cascade calculation with full -nucleus final-state interactions. The Primakoff, nuclear coherent and nuclear incoherent components of the cross sections fit remarkably well previous measurements for Be and Cu from Cornell, suggesting a destructive interference between the Coulomb and nuclear coherent amplitudes for Cu. The inelastic background of the data is consistently attributed to the nuclear incoherent part, which is clearly not isotropic as previously considered in Cornell's analysis. A renewed interest in the Primakoff method appeared with the advent of the PrimEx Collaboration at the Jefferson Laboratory, which will provide a more precise measurement of ÿ 0 ! [9]. Furthermore, high precision and 0 photoproduction experiments are strongly encouraged by the forthcoming 12 GeV upgrade of the electron beam, demanding reliable methods for the accurate delineation of the nuclear background.The approaches developed so far for incoherent photoproduction from nuclei are restricted to 1 GeV, where the contribution from the S 11 1535 resonance largely dominates. The final-state interactions (FSI) of the mesons are taken into account either using optical potentials [10], the quantum molecular dynamics (QMD) model of Ref. [11], or the Boltzmann-Uehling-Uhlenbeck (BUU) transport model [12]. Obviously, these important theoretical developments are not suitable to describe incoherent production at higher energies.In this Letter, we present for the first time a consistent solution for the puzzling scenario of ÿ ! from Cornell using the multicollisional intranuclear cascade model MCMC [13][14][15] to describe the nuclear background. The Monte Carlo (MC) method takes into account incoherent photoproduction from nuclei at forward angles within 4 to 9 GeV, including -nucleus FSI via a multiple scattering framework.The forward angle photoproduction cross section is assumed to be in the form [16 -18] where T P , T NC , and T NI are the Primakoff (P), nuclear coherent (NC), and nuclear incoherent (NI) amplitudes, respectively, with ' representing the P-NC phase shift. The Coulomb amplitude is the sum of the amplitudes from the protons [6], such thatwhere 1=137, Z is the atomic number, k the photon energy, Q the four momentum transfer,F C k; the Coulomb form factor (FF) including -nucleus FSI; with ÿ ! , , , and representing the decay width, velocity, mass, and production angle of the meson, respectively. PRL 101, 012301 (2008)

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η→γγDecay Width via the Primakoff Cross Section

et al. 2008

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“…The final state interactions of the outgoing η meson are taken into account. This fully non-local model has been discussed recently for the cases of exclusive and incoherent photoproduction [15,16]. These non-local calculations, in contrast to earlier local ones [17], allow us to include possible density dependent changes in the mass and width of the resonances in the nuclear medium.…”

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Inclusive photoproduction of η mesons on nuclei and the in-medium properties of theS11resonance

Hedayati-Poor¹,

Sherif

2007

Phys. Rev. C

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A relativistic non-local model for the inclusive photoproduction of η mesons from complex nuclei is introduced. The model is based on the dominance of the S 11 (1535) resonance. We compare the results of our calculations with the available data on inclusive cross sections for the nuclei C, Al and Cu. Assuming the resonance propagates freely in the nuclear medium, we find that the calculated angular distribution and energy dependence of the cross sections reproduce the data in a reasonable fashion. The present non-local model allows the inclusion of density dependent mass and width in the calculations. Including these in the calculations reveals that the presently available data do not show clear preference for the inclusion of such modifications of the properties of the S 11 (1535) in the nuclear medium.

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Nuclear incoherent photoproduction ofπ0andηfrom 4 to 12 GeV

Rodrigues¹,

Arruda‐Neto²,

Mesa³

et al. 2010

Phys. Rev. C

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The mechanism of incoherent π 0 and η photoproduction from complex nuclei is investigated from 4 to 12 GeV with an extended version of the multicollisional Monte Carlo (MCMC) intranuclear cascade model. The calculations take into account the elementary photoproduction amplitudes via a Regge model and the nuclear effects of photon shadowing, Pauli blocking, and meson-nucleus final-state interactions. The results for π 0 photoproduction reproduced for the first time the magnitude and energy dependence of the measured rations σ γ A /σ γ N for several nuclei (Be, C, Al, Cu, Ag, and Pb) from a Cornell experiment. The results for η photoproduction fitted the inelastic background in Cornell's yields remarkably well, which is clearly not isotropic as previously considered in Cornell's analysis. With this constraint for the background, the η → γ γ decay width was extracted using the Primakoff method, combining Be and Cu data [ η→γ γ = 0.476 (62)

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New calculations for incoherent eta photoproduction on nuclei including nonlocal and medium effects

Cited by 3 publications

References 23 publications

η→γγDecay Width via the Primakoff Cross Section

η→γγDecay Width via the Primakoff Cross Section

Inclusive photoproduction of η mesons on nuclei and the in-medium properties of theS11resonance

Nuclear incoherent photoproduction ofπ0andηfrom 4 to 12 GeV

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