An Analysis Of Hadron Structure In Covariant Chiral Effective Theory

In particle physics,hadron structures have always been the central issues.The fundamental theory for strong interaction is quantum chromodynamics(QCD),however,one could not directly apply to the hadron structures in low energy processes due to nonperturbative effects.Since 1970's,chiral perturbation theory(ChPT)has been established as a low-energy effective theory for QCD.Incorporating hadrons as elementary degrees,ChPT is organized by the chiral symmetry(low energy symmetry of QCD)and could be applied to hadron dynamics in a systematic manner,making impressive successes in hadron(especially in pion)physics.Nevertheless,ChPT becomes problematic in the processes carrying baryons:working with covariant formalism,one would get large pieces that violate chiral power counting;working with the so-called heavy baryon formalism(HBChPT),chiral power counting is explicitly preserved,but theory is not trustworthy across the thresholds of baryons.In literature,people proposed various forms of regularization to cope with the issue.In this thesis,we will compute the hadron structure functions in covariant ChPT as it is more trustworthy compared to HBChPT.We find that,all the terms that violate chiral power counting are local and could be readily removed through counter terms for UV divergences.What remains are well defined ones that obey chiral power counting.Our investigation showed that,calculating the structure functions of baryons using covariant formalism of chiral effective theory,one could obtain trustworthy analytical results without violating chiral power counting,lending further support to the theoretical studies of nucleon or baryon structures using covariant formalism.