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S. Scopetta

Publications and source records attributed to S. Scopetta.

47 records · Page 3Linked to original sources
arXiv1997

Nucleon and nuclear spin structure functions

Nuclear effects in polarized inelastic electron scattering off polarized $^3He$ and polarized $^2H$ are discussed; in the resonance region, Fermi motion effects are found to be much larger than in deep inelastic scattering. It is shown that improperly describing nuclear dynamics would lead to the extraction of unreliable neutron spin structure functions; on the other hand side, simple and workable equations, relating the Gerasimov -- Drell -- Hearn Integral for the neutron to the corresponding quantity for $^3He$ and $^2H$, are proposed. Nuclear effects in the recent E143 data are estimated by a proper procedure.

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arXiv1997

Polarization Phenomena in Small-Angle Photoproduction of e+e- Pairs and the Gerasimov-Drell-Hearn Sum Rule

Photoproduction of $e^+e^-$ pairs at small angles is investigated as a tool to determine the functions $f_1$ and $f_2$ entering the real-photon forward Compton scattering amplitude. The method is based on an interference of the Bethe-Heitler and the virtual Compton scattering mechanisms, generating an azimuthal asymmetry in the $e^+$ versus $e^-$ yield. The general case of a circularly polarized beam and a longitudinally polarized target allows one to determine both the real and imaginary parts of $f_1$ as well as $f_2$. The imaginary part of $f_2$ requires target polarization only. We calculate cross sections and asymmetries of the reaction $p(γ,e^+e^-)p$, estimate corrections and backgrounds, and propose suitable kinematical regions to perform the experiment. Our investigation shows that photoproduction of $e^+e^-$-pairs off the proton and light nuclei may serve as a rather sensitive test of the validity of the Gerasimov-Drell-Hearn sum rule.

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arXiv1996

Tagging nucleon structure functions by heavy particle detection in deep inelastic electron-ion scattering

It is shown that in deep inelastic electron - ion collisions the detection, in coincidence with the scattered electron, of a nucleus A-1 in the ground state, as well as a nucleon and a nucleus A-2 also in the ground state, may provide unique information on several long standing problems, such as the origin of the EMC effect, the possible medium modifications of the nucleon structure functions, and the nature of Nucleon-Nucleon correlations.

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arXiv1996

On the Extraction of the Neutron Spin Structure Functions and the Gerasimov -- Drell -- Hearn Integral from $^3\vec {He}(\vec e, e')X$ data

Nuclear effects in polarized inelastic electron scattering off polarized $^3He$ are discussed; in the kinematics of future experiments at CEBAF, Fermi motion effects are found to be much larger than in deep inelastic scattering. It is shown that improperly describing nuclear dynamics would lead to the extraction of unreliable neutron spin structure functions. On the other hand side, a simple and workable equation relating the Gerasimov -- Drell -- Hearn Integral for the neutron to the corresponding quantity for $^3He$ is proposed.

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arXiv1996

Spin Structure Function of the Deuteron in the Resonance Region and the GDH Sum Rule for the Neutron

The nuclear effects in the spin-dependent structure function $g_1$ of the deuteron are studied in the kinematics of future experiments at CEBAF, ($ν\leq 3~GeV, ~Q^2 \leq 2~GeV^2$). The magnitude of the nuclear effects is found to be significantly larger than the one occurring in deep inelastic scattering ($ν\to \infty, ~Q^2\to \infty$). We discuss the mechanism leading to large effects in the region of the nucleon resonances. A possibility to measure the neutron structure functions in the CEBAF experiments with deuterium is analysed, and conclusions about the experimental study of the $Q^2$ dependence of the Gerasimov-Drell-Hearn Sum Rule for the neutron are drawn.

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arXiv1996

The Neutron Spin Structure Function from the Deuteron Data in the Resonance Region

Nuclear effects in the spin-dependent structure function $g_1$ of the deuteron are studied in the kinematics of future experiments at CEBAF, ($ν\leq 3~GeV, ~Q^2 \leq 2~GeV^2$). The magnitude of nuclear effects is found to be significantly larger than the one occurring in deep inelastic scattering ($ν\to \infty, ~Q^2\to \infty$). A possibility to measure the neutron structure functions in the CEBAF experiments with deuterium is analysed. It is found that disregarding or improperly treating nuclear effects in the region of nucleon resonances would lead to the ``extraction" of an unreliable function. A procedure aimed at correctly extracting the neutron structure function from the deuterium data is illustrated and conclusions about the experimental study of the $Q^2$ dependence of the Gerasimov-Drell-Hearn Sum Rule for the neutron are drawn.

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arXiv1994

The Spin-Dependent Structure Functions of Nuclei in the Meson-Nucleon Theory

A theoretical approach to the investigation of spin-dependent structure functions in deep inelastic scattering of polarized leptons off polarized nuclei, based on the effective meson-nucleon theory and operator product expansion method, is proposed and applied to deuteron and $^3He$. The explicit forms of the moments of the deuteron and $^3He$ spin-dependent structure functions are found and numerical estimates of the influence of nuclear structure effects are presented.

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arXiv1993

Nuclear effects in Deep Inelastic Scattering of polarized electrons off polarized 3He and the neutron spin structure functions

It is shown that the nuclear effects playing a relevant role in Deep Inelastic Scattering of polarized electrons by polarized $^3$He are mainly those arising from the effective proton and neutron polarizations generated by the $S'$ and $D$ waves in $^3$He. A simple and reliable equation relating the neutron, $g_1^n$, and $^3$He, $g_1^3$, spin structure functions is proposed. It is shown that the measurement of the first moment of the $^3$He structure function can provide a significant check of the Bjorken Sum Rule.

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