Keywords (Extracted from title, table of contents and abstract of thesis)
qcd, nuclear shadowing, quarkonium processes, perturbative qcd, lps model, landshoffpolkinghorneshort model, quarknucleon scattering, quarknucleus scattering, leptonic decays, hadronic decays 
Abstract In this thesis shortdistance (hard momentum transfer) processes are explored using perturbative QCD. Three problems, as described below, were studied. In the first research problem the low x behaviour of the twisttwo structure functions F2D(x), g1D(x) and b1D(x) for the deuteron was examined in the framework of the LPS (LandshoffPolkinghorneShort) model for deep inelastic scattering. Glauber theory was used to go from quarknucleon scattering to quarknucleus scattering. The quadrupole structure function b1D(x, Q2), which otherwise vanishes for a pure sstate, turns out to be nonzero once double scattering terms are included. Assuming a simple sstate model of the deuteron, numerical estimates were given for all twisttwo structure functions, both spin dependent and independent. In the second problem, processes involving heavy quarkonia were studied. I have developed a systematically improvable method of incorporating gauge invariance in heavy quarkonia processes and thereby corrected an important defect of the traditional nonrelativistic quark model. The method yields relativistic correction of O( v2), where v is the relative quark velocity, in heavy quarkonia decays, etc. It was found that corrections arising from the incorporation of gauge symmetry are important for decay, fragmentation and formation processes involving QQ systems. The contribution of soft gluons was also shown to be of higher order in v and so is negligible for calculations done upto O( v2). In the third, and final, problem the formalism described above was applied, upto terms of O(v2), to the photoproduction of J/Ïˆ on nucleons. The bound state corrections to this process were calculated in the coloursinglet model. The internal structure of the meson is characterised by two parameters, EB / M and V2 Ïˆ (O)/M2 Ïˆ(O), in addition to the usual wavefunction at the origin Ïˆ(O). The parameters were constrained to be consistent with measured leptonic and hadronic decays of the J/ Ïˆ. It was found that the calculated corrections to the colour singlet model, which include radiative effects, improve agreement with the experimental data.
