Chiral dynamics and peripheral transverse densities
2014 (English)In: Journal of High Energy Physics (JHEP), ISSN 1029-8479, E-ISSN 1126-6708, no 1, 092- p.Article in journal (Refereed) Published
In the partonic (or light-front) description of relativistic systems the electromagnetic form factors are expressed in terms of frame-independent charge and magnetization densities in transverse space. This formulation allows one to identify the chiral components of nucleon structure as the peripheral densities at transverse distances b = O(M-pi(-1)) and compute them in a parametrically controlled manner. A dispersion relation connects the large-distance behavior of the transverse charge and magnetization densities to the spectral functions of the Dirac and Pauli form factors near the two-pion threshold at time-like t = 4M(pi)(2), which can be computed in relativistic chiral effective field theory. Using the leading-order approximation we (a) derive the asymptotic behavior (Yukawa tail) of the isovector transverse densities in the "chiral" region b = O(M-pi(-1)) and the "molecular" region b = O(M-N(2)/M-pi(3)); (b) perform the heavy-baryon expansion of the transverse densities; (c) explain the relative magnitude of the peripheral charge and magnetization densities in a simple mechanical picture; (d) include Delta isobar intermediate states and study the peripheral transverse densities in the large-N-c limit of QCD; (e) quantify the region of transverse distances where the chiral components of the densities are numerically dominant; (f) calculate the chiral divergences of the b(2)-weighted moments of the isovector transverse densities (charge and anomalous magnetic radii) in the limit M-pi -> 0 and determine their spatial support. Our approach provides a concise formulation of the spatial structure of the nucleon's chiral component and offers new insights into basic properties of the chiral expansion. It relates the information extracted from low-t elastic form factors to the generalized parton distributions probed in peripheral high-energy scattering processes.
Place, publisher, year, edition, pages
2014. no 1, 092- p.
Chiral Lagrangians, Parton Model, 1/N Expansion
IdentifiersURN: urn:nbn:se:uu:diva-220301DOI: 10.1007/JHEP01(2014)092ISI: 000330646000005OAI: oai:DiVA.org:uu-220301DiVA: diva2:705544