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Semi-inclusive Deep Inelastic Electron Scattering off the Deuteron and the Neutron to Proton Structure Function Ratio

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 نشر من قبل Silvano Simula
 تاريخ النشر 1996
  مجال البحث
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 تأليف Silvano Simula




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The production of slow nucleons in semi-inclusive deep inelastic electron scattering off the deuteron is investigated in the region $x gsim 0.3$. It is shown that within the spectator mechanism the semi-inclusive cross section exhibits a scaling property even at moderate values of $Q^2$ ($sim$ few $(GeV/c)^2$) accessible at present facilities, like $CEBAF$. Such a scaling property can be used as a model-independent test of the dominance of the spectator mechanism itself and provides an interesting tool to investigate the neutron structure function. The possibility of extracting model-independent information on the neutron to proton structure function ratio from semi-inclusive experiments is illustrated. The application of the spectator scaling to semi-inclusive processes off complex nuclei is outlined.



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218 - Silvano Simula 1996
The production of slow nucleons in semi-inclusive deep inelastic electron scattering off the deuteron is investigated in the region $x gsim 0.3$ for kinematical conditions accessible at $HERA$. Within the spectator mechanism the semi-inclusive cross section exhibits a scaling property, which can be used as a model-independent test of the dominance of the spectator mechanism itself, providing in this way an interesting tool to investigate the neutron structure function. The possibility of extracting model-independent information on the neutron to proton structure function ratio from semi-inclusive experiments is also illustrated.
The effects of the final state interaction in slow proton production in semi inclusive deep inelastic scattering processes off nuclei, A(e,ep)X, are investigated in details within the spectator and target fragmentation mechanisms; in the former mecha nism, the hard interaction on a nucleon of a correlated pair leads, by recoil, to the emission of the partner nucleon, whereas in the latter mechanism proton is produced when the diquark, which is formed right after the visrtual photon-quark interaction, captures a quark from the vacuum. Unlike previous papers on the subject, particular attention is paid on the effects of the final state interaction of the hadronizing quark with the nuclear medium within an approach based upon an effective time-dependent cross section which combines the soft and hard parts of hadronization dynamics in terms of the string model and perturbative QCD, respectively. It is shown that the final state interaction of the hadronizing quark with the medium plays a relevant role both in deuteron and complex nuclei; nonetheless, kinematical regions where final state interaction effects are minimized can experimentally be selected, which would allow one to investigate the structure functions of nucleons embedded in the nuclear medium; likewise, regions where the interaction of the struck hadronizing quark with the nuclear medium is maximized can be found, which would make it possible to study non perturbative hadronization mechanisms.
The semi-inclusive deep inelastic scattering of electrons off a nucleus A with detection of a slow nucleus (A-1) in the ground or low excitation states, i.e. the process A(e,e(A-1))X, can provide useful information on the origin of the EMC effect and the mechanisms of hadronization. The theoretical description of the process is reviewed and the results of several calculations on few-body systems and complex nuclei are presented.
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The semi-inclusive deep inelastic scattering of electrons off the deuteron ($^2H equiv D$) and $^3He$ with detection of slow protons and deuterons, respectively, i.e. the processes $D(e,ep)X$ and $^3He(e,eD)X$, are calculated within the spectator mec hanism, taking into account the final state interaction of the hadronizing quark with the detected protons and deuterons, respectively. It is shown that by a proper choice of the kinematics the origin of the EMC effect and the details of the interaction between the hadronizing quark and the nuclear medium can be investigated at a level which cannot be reached by inclusive deep inelastic scattering. A comparison of our calculations with recently available experimental data on the process $D(e,ep)X$ shows a good agreement in the backward hemisphere of the emitted nucleons. Theoretical predictions at the energies thyat will be available at the upgraded Thomas Jefferson National Accelerator Facilty are presented, and the possibility to investigate the proposed semi-inclusive processes at electron-ion colliders is briefly discussed.
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