Hadronic scattering amplitudes: Medium-energy constraints on asymptotic behavior

Cudell, Jean-René; Ежела, В. В.; Gauron, P.; Kang, Kyungsik; Kuyanov, Yu.V.; Lugovsky, S. B.; Nicolescu, B.; Ткаченко, Н. П.

doi:10.1103/physrevd.65.074024

Cited by 140 publications

(231 citation statements)

References 46 publications

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“…decay width has been measured in two-photon experiments [5] and via the Primakoff effect [6] at Cornell [7], leading to extremely discrepant results. While the twophoton measurements are consistent with each other, Cornell's measurement [0.324(46) keV] is severely below their average, and was recently excluded from the Particle Data Group (PDG) world average [0.510 (26) keV] [8]. Such a long-standing issue is strong evidence of a misunderstanding of the hadronic inelastic background in the Cornell analysis.…”

mentioning

confidence: 75%

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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confidence: 75%

η→γγDecay Width via the Primakoff Cross Section

et al. 2008

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“…On the other hand, the NC cross section scales with A 2 [Eq. (51)] and one should expect that a single parameter, namely a NC , should fit simultaneously the complex nuclei data from Be and Cu. However, the magnitude of the NC cross section is also sensitive to FSI, which are in principle included in the FF calculations.…”

Section: Extracting the η → γ γ Decay Width Via The Primakoff Methodmentioning

confidence: 99%

“…However, as will be discussed later, the π 0 -nucleon interaction probability is considered in the MCMC model taking into account the total cross section σ π 0 N→Total , instead of the sum of all channels from Table II. The total cross section, on the other hand, is assumed to be the average (σ π + p→Total + σ π − p→Total )/2. The cross sections σ π + p→Total and σ π − p→Total are then obtained by fitting the available data using the Regge parametrization [51]: Table II for the input channels π 0 p and π 0 n. Fig. 9.…”

Section: E Meson-nucleus Final-state Interactionsmentioning

confidence: 99%

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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“…For a review of the current knowledge about the structure of the Pomeron, we refer to [14]. Recent thorough analyses of different classes of parametrizations of the asymptotic amplitudes and of the corresponding fits to the large body of available data are described in [15,16]. These indicate that the leading terms can be determined rather well by applying factorization to the experimentally well explored NN and πN scattering amplitudes, but the non-leading contributions become more and more important as the energy is lowered (see, e.g., [16] for a critical discussion of the range of applicability of different asymptotic formulae).…”

Section: Asymptoticsmentioning

confidence: 99%

“…Recent thorough analyses of different classes of parametrizations of the asymptotic amplitudes and of the corresponding fits to the large body of available data are described in [15,16]. These indicate that the leading terms can be determined rather well by applying factorization to the experimentally well explored NN and πN scattering amplitudes, but the non-leading contributions become more and more important as the energy is lowered (see, e.g., [16] for a critical discussion of the range of applicability of different asymptotic formulae). We do not consider it plausible that the asymptotic representation of PY can be trusted to the precision claimed in that paper, where the uncertainties in the contributions from the region above 1.42 GeV are estimated at 10 to 15 %.…”

Section: Asymptoticsmentioning

confidence: 99%

On the precision of the theoretical predictions forππscattering

et al. 2003

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In a recent paper, Peláez and Ynduráin evaluate some of the low energy observables of ππ scattering and obtain flat disagreement with our earlier results. The authors work with unsubtracted dispersion relations, so that their results are very sensitive to the poorly known high energy behaviour of the scattering amplitude. They claim that the asymptotic representation we used is incorrect and propose an alternative one. We repeat their calculations on the basis of the standard, subtracted fixed-t dispersion relations, using their asymptotics. The outcome fully confirms our earlier findings. Moreover, we show that the Regge parametrization proposed by these authors for the region above 1.4 GeV violates crossing symmetry: Their ansatz is not consistent with the behaviour observed at low energies.

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Hadronic scattering amplitudes: Medium-energy constraints on asymptotic behavior

Cited by 140 publications

References 46 publications

η→γγDecay Width via the Primakoff Cross Section

η→γγDecay Width via the Primakoff Cross Section

Nuclear incoherent photoproduction ofπ0andηfrom 4 to 12 GeV

On the precision of the theoretical predictions forππscattering

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