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Title of Thesis

Hafsa Khan
Institute/University/Department Details
Department of Physics/ Quaid-i-Azam University, Islamabad
Number of Pages
Keywords (Extracted from title, table of contents and abstract of thesis)
qcd, nuclear shadowing, quarkonium processes, perturbative qcd, lps model, landshoff-polkinghorne-short model, quark-nucleon scattering, quark-nucleus scattering, leptonic decays, hadronic decays

In this thesis short-distance (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 twist-two structure functions F2D(x), g1D(x) and b1D(x) for the deuteron was examined in the framework of the LPS (Landshoff-Polkinghorne-Short) model for deep inelastic scattering. Glauber theory was used to go from quark-nucleon scattering to quark-nucleus scattering. The quadrupole structure function b1D(x, Q2), which otherwise vanishes for a pure s-state, turns out to be non-zero once double scattering terms are included. Assuming a simple s-state model of the deuteron, numerical estimates were given for all twist-two 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 non-relativistic 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/ˆ on nucleons. The bound state corrections to this process were calculated in the colour-singlet model. The internal structure of the meson is characterised by two parameters, EB / M and V2 ˆ (O)/M2 ˆ(O), in addition to the usual wavefunction at the origin ˆ(O). The parameters were constrained to be consistent with measured leptonic and hadronic decays of the J/ ˆ. It was found that the calculated corrections to the colour singlet model, which include radiative effects, improve agreement with the experimental data.

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1240.63 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents 0
68.71 KB
2 1 Introduction 1
153.59 KB
  1.1 A Bit Of History 1
  1.2 QCD As A Gauge Theory 3
  1.3 QCD As A Perturbative Theory 4
  1.4 Some Applications Of Perturbative Qcd 6
  1.5 A Brief Description Of Ph.D Research 9
3 2 Shadowing Of Deuteron Spin Structure Functions 15
280.63 KB
  2.1 Lepton-Hadron DIS Viewed As A Q - N Or q - N Scattering Process 18
  2.2 Results And Discussion 33
4 3 Systematic Gauge- Invariant Approach To Heavy Quarkonium Decays 42
282.18 KB
  3.1 Gauge Principle 44
  3.2 Gauge Invariance In Heavy Quarkonium Decays 47
  3.3 Application 56
  3.4 Comparison 64
5 4 Beyond The Colour-Singlet Model For Inelastic J/ˆ Photoproduction 70
198.9 KB
  4.1 The Colour-Singlet Model 72
  4.2 A Review Of The Formalism 75
  4.3 γ+g†’ J/ˆ +g 78
  4.4 Results And Discussion 84
6 5 The Q - D Amplitude In The Glauber Approximation 91
420.16 KB
  5.1 Regge Theory 94
  5.2 Invariant Matrix Elements For 0 -+ 98
  5.3 Non-Relativistic Reduction Of The Bethe-Salpeter Equation 105
  5.4 Extraction Of Bound-State Coefficients 109
  5.5 Mathematica Programs 112