Experimental Study of Nuclear Shadowing in Low-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi>Q</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>Electroproduction

Eickmeyer, J.; Michalowski, S. J.; Mistry, N. B.; Talman, R.; Ueno, K.

doi:10.1103/physrevlett.36.289

Cited by 35 publications

(10 citation statements)

References 11 publications

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“…At large Q 2 the nuclear shadowing function s p (A) expressed in eq. (27), which was used for the approximations of the photonuclear cross-section, can converge to 1 with increasing Q 2 as the shadowing effect seems to be smaller for virtual photons [88], but at present this effect is not well measured. The low energy nature of the GDR effects proves that the additional form factor must be used for σ γ * in the GDR region, but this effect is also unmeasured.…”

Section: Approximation Of the Q 2 -Dependence Of Electronuclear Reactmentioning

confidence: 99%

Approximation of photonuclear interaction cross-sections

Kossov¹

2002

Eur Phys J A

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Abstract. Photonuclear interaction cross-sections from the GEANT4 database are approximated for all nuclei and all energies (from the hadron production threshold to about 40 TeV). The approximation methods in the giant-dipole resonance region, nucleon resonance region, and high-energy region are improved with respect to existing approximations. As an application of the approximation for photonuclear cross-sections, an improved method of calculating electronuclear cross-sections is developed. The interaction cross-section of virtual photons with nuclei at high Q 2 are approximated and a simple algorithm for describing the electronuclear reactions, including high-Q 2 scattering, is proposed.

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Section: Approximation Of the Q 2 -Dependence Of Electronuclear Reactmentioning

confidence: 99%

Approximation of photonuclear interaction cross-sections

Kossov¹

2002

Eur Phys J A

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“…VMD models do, however, have difficulty accounting for the rapid decrease of shadowing when the photons become slightly spacelike. 8 More data will be useful for suggesting the direction in which models must be elaborated.…”

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confidence: 98%

Measurement of Shadowing in Photon-Nucleus Total Cross Sections from 20 to 185 GeV

et al. 1979

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We have measured total hadronic photoproduction cross sections on carbon, copper, and lead. Tagged-photon energies ranged from 20 to 185 GeV for copper and from 45 to 82 GeV for carbon and lead. The energy and A dependence of shadowing were computed by comparing these results to the hydrogen cross section as measured nearly simultaneously with the same apparatus. We observed somewhat more shadowing than did most experiments at lower photon energies.The photoproduction cross section from complex nuclei should be less than the sum of individual nucleon cross sections because (naively) some nucleons "shadow" others by absorbing out the hadronic part of the photon beam. This effect has been observed in photoproduction by real photons of up to 18 GeV. 1 " 6 Although the results of Ref. 1 disagreed with the vector-meson-dominance (VMD) model used in that paper, it is possible to find models 7 that do give reasonable agreement with the shadowing observed in photoproduction. VMD models do, however, have difficulty accounting for the rapid decrease of shadowing when the photons become slightly spacelike. 8 More data will be useful for suggesting the direction in which models must be elaborated.We have measured the dependence of the total photoproduction cross section on A, the atomic weight of the target nucleus. One reason for doing so was to get a more accurate measurement of shadowing than has been hitherto possible. The cross section is easier to measure at high energies and our apparatus was designed to achieve the very high precision needed for detecting the small energy dependence of the hydrogen cross section. 9 Another reason for doing this measurement was to extend the energy range of shadowing data. Such an extension could, for example, show effects of higher-mass states. The higher the mass of a vector state, the higher the photon energy must be in order that the state contribute to shadowing. In fact, neutron and K L cross sections on nuclei do show an increase in the amount of shadowing with increasing energy,, 10 " 12 This increase can be interpreted as an effect of "inelastic screening" 13 of the forward scattering amplitude, in which an incident hadron diffractively dissociates (into a possibly higher-mass state) at one point within the nucleus and recombines at another. In VMD calculations of shadowing, this would correspond to including off-diagonal terms.The measurement was performed in the Fermilab tagged-photon beam. Tagged photons were produced from copper radiators of 6 and 15 mils (0.0107 and 0.0267 radiation lengths). The beam, detection apparatus, and trigger were the same as used in a measurement of the total photoproduction cross section on hydrogen. 9 However, the hydrogen target was replaced by carbon, copper, and lead targets-each a rectangle larger than the beam and each of approximately 0.1 radiation length in thickness. These targets were mounted in a vacuum box so that each could be rotated into the beam. An empty target slot permitted measurement and subtraction of the rate of hadronic...

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“…One should notice, however, that at small Q2 a shadowing effect is observed for x < 0. 1 (93,94), which implies that the iron over deuterium ratio cannot be completely Q2 independent.…”

Section: Comparison Of Iron and Deuterium Structure Functionsmentioning

confidence: 97%