In this thesis we present the work we have done to further the understandingof neutral pion photoproduction from the proton. Our work used heavybaryonchiral perturbation theory to fourth order, and we explicitly include the ∆(1232)resonance using the delta powercounting scheme. We also test the effects of includingand excluding Dwaves, partial waves with orbital angular momentum quantumnumber of 2.We begin our discussion in chapter 1 with a brief history of nuclear physicsbefore showing how current algebras and the partialconservation of the axialvector current (PCAC) can be used to describe lowenergy hadronic interactions.To improve upon PCAC results, one can make use of chiral effective field theories,taking advantage of the chiral symmetry that is present in the limit of masslessquarks. We formally introduce chiral perturbation theory (χPT) in chapter 2,discussing the powercounting problem that arises once baryons are included, andpresent two different approaches to overcome this. We conclude chapter 2 showinghow the theory can be extended to include the ∆(1232) resonance.In chapter 3 we describe the modelindependent framework of pion photoproduction needed to describe both theory and experiment. We discuss the variousrecent efforts to describe pion photoproduction within χPT in the latter half ofchapter 3.We lay out the framework we have developed in chapter 4 and present ourresults in chapter 5. We have compared our work to the recent experimental datareleased by the A2 and CBTAPS collaborations at the Mainz Microtron[22]. Ourresults show that we can accurately describe the data from threshold up to an incoming laboratory photon energy of approximately 260 MeV, a clear improvementon previous studies [1416, 19, 2327]. We find that including the ∆ is necessaryto describe the data beyond E γ ≈ 200 MeV, but the case for Dwaves is not soclear. We cannot pinpoint an energy where their inclusion is necessary but we dofind evidence suggesting they are important to improve the stability of the fit. Ourbest results require the inclusion of both the ∆ and Dwaves.Finally, in chapter 6, we present our concluding remarks from what has beenachieved over the last four years of study and what forms possible extensions ofour work could take.
Date of Award  1 Aug 2017 

Original language  English 

Awarding Institution   The University of Manchester


Supervisor  Judith McGovern (Supervisor) & Niels Walet (Supervisor) 

 perturbation
 chiral
 theory
 delta
 mainz
 proton
 pion
 hadron
 photoproduction
Understanding Pion Photoproduction using Chiral Perturbation Theory
Cawthorne, L. (Author). 1 Aug 2017
Student thesis: Phd