Testing the Hidden Local Symmetry Model

Prudden, Mark (1988) Testing the Hidden Local Symmetry Model. PhD thesis, University of Glasgow.

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The aim of this thesis is to test the recently proposed effective Lagrangian for pi, rho and gamma physics, called the Hidden Local Symmetry (HLS) model, against experimental data on the process gammagamma→rhorho. To this end Chapter 1 is a general introduction, motivating the interest in studying the HLS model in particular and pointing out its relation to composite models of Higgs and W/Z bosons. It is noted that there is a crucial sector of this model that has, until now, remained untested. It is observed that this untested sector can be probed by comparing the predictions of the model with the well established data on gammagamma→rhorho; which in itself is an interesting process and in need of better theoretical understanding. Chapter 2 is an introduction to the HLS model and in section (i) the construction of the model Lagrangian is presented. The HLS model has an arbitrary parameter 'a', it is shown in section (ii) that so far the attempts to determine 'a' by some "underlying" symmetry principle fail when confronted with phenomenology. In section (iii) the pivotal role of the HLS model of vector mesons in the Skyrmion picture of baryon physics is explained. Section (iv) summarises the chapter and underlines the need to test the HLS model fully. Chapter 3 is a summary of the current experimental and theoretical status of gammagamma→V1V2 physics (V1,2=rho, o, k*, ϕ). It is emphasised that there is still room for a "conventional explanation" of the process gammagamma→rhorho. Thus the second strand of the thesis is testing the possibility of the HLS model explaining the data on gammagamma-rhorho. Chapter 4 is the first order, or tree-level, calculation of gammagamma→rhorho in the HLS model, it is found to be in disagreement with experimental data. Which leads us to consider in chapter 5 the motivation for a one loop calculation of gammagamma→rhorho; the approach taken in estimating the loop corrections, in the spirit of chiral perturbation theory, is outlined. In chapter 6 the loop diagram calculation for gammagamma→pp is presented, the results indicate that the perturbative expansion fails. It is thus necessary to check this result before proceeding any further with the loop calculation. The rho+rho- scattering amplitudes in the HLS model are shown to violate unitarity in chapter 7, this is an independent check on the loop diagram 'calculation in chapter 6. In chapter 8 it is concluded that the HLS model fails to describe gammagamma→rhorho perturbatively. The discussion of the results of this thesis includes an outline of several interesting possibilities for future work.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Nuclear physics and radiation, Theoretical physics
Date of Award: 1988
Depositing User: Enlighten Team
Unique ID: glathesis:1988-77730
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jan 2020 11:53
Last Modified: 14 Jan 2020 11:53
URI: https://theses.gla.ac.uk/id/eprint/77730

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