Deep inelastic lepton scattering

Fig. 15.4. Feynman diagram for deep inelastic lepton-nucleon scattering eN eX.

In the previous chapters we saw that in so far as deep inelastic lepton-nucleon scattering was concerned the nucleon could be visualized as a bound system of constituent quark-partons, with which the lepton interacted as if they were free particles. Our aim now is to try to give some sort of justification for such a picture, and to derive more reliable results for deep inelastic scattering in which allowance is made for the internal longitudinal and transverse (Fermi) motion of the quark-partons. The approach also allows us to evaluate the forward hadronic matrix elements of currents which appear in the sum rules discussed in Chapters 16 and 17 in terms of parton number densities. 

In Sections 15.6, 16.8 and 17.1.2 we emphasized the consequences of the European Muon Collaboration s (EMC) unexpected results in an experiment in 1987 on polarized deep inelastic lepton-hadron scattering, and we stressed the importance of testing the Bjorken sum rule by comparing neutron and proton data. 

We have enlarged the treatment of deep inelastic lepton-hadron scattering in three directions. Catalyzed by the major discoveries of the European Muon Collaboration there is a more detailed treatment of both polarization effects and of nuclear eflFects. And in anticipation of HERA we discuss interference which will be important for large physics. 

In Chapters 15 and 16 we developed the theory of deep inelastic scattering from a very general point of view, using the general structure of the cross-section in terms of the three scaling functions Fj x). FVom their experimental behaviour we were led to the quark-parton picture in which a virtual photon, or emitted at the lepton vertex interacts with a quark or antiquark in the target hadron. At the level of the simple... 

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