Low momentum transfer theorem for two photon exchange in lepton hardron scattering

Journal Article · Tue Sep 01 04:00:00 EDT 1981 · Ann. Phys. (N.Y.); (United States)

DOI:https://doi.org/10.1016/0003-4916(81)90157-3· OSTI ID:5870958

Penarrocha, J A; Bernabeu, J

The two photon contribution to lepton-hardon scattering is considered. Under the assumptions of Lorentz covarience, gauge invarience, unitarity, and analyticity, we prove a low momentum transfer theorem for the relevant amplitudes. Fixed energy dispersion relations tell us that their nonanalytic part, in the neighbourhood of t = 0, is given by the contribution of the two photon cut in the t-channel. The t-channel absorptive parts are obtained from unitarity. Their calculation has as input the two amplitudes corresponding to Compton scattering on the hadron with a pole contribution, and the continuum controlled at low t by the electromagnetic polarizabilities. By means of the dispersion integral, one proves the expansion k/sub 1/(s)+k/sub 2/(s)..sqrt..-t+k/sub 3/(s)tlog(-t)+O(t) for the continuum contribution, where k/sub 1/(s) is the only unknown. Explicit expressions are obtained for the pole contribution as M..-->..infinity, where M is the hadron mass, and for the continuum when (-t)<..lambda.. and (-t)< 4m/sup 2/, where m is the muon mass and ..lambda.. is a characteristic parameter of the hadron structure.

• Research Organization: Department of Theoretical Physics, Faculty of Physics, Unversity of Valencia, Spain
• OSTI ID: 5870958
• Journal Information: Ann. Phys. (N.Y.); (United States), Journal Name: Ann. Phys. (N.Y.); (United States) Vol. 135:2; ISSN APNYA
• Country of Publication: United States
• Language: English

Related Subjects

645202* -- High Energy Physics-- Particle Interactions &amp; Properties-Theoretical-- Electromagnetic Interactions &amp; Properties
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
AMPLITUDES
BASIC INTERACTIONS
COMPTON EFFECT
DISPERSION RELATIONS
ELASTIC SCATTERING
ELECTRODYNAMICS
ELECTROMAGNETIC INTERACTIONS
FIELD THEORIES
GAUGE INVARIANCE
HELICITY
INTERACTIONS
INVARIANCE PRINCIPLES
LEPTON-HADRON INTERACTIONS
LORENTZ INVARIANCE
MOMENTUM TRANSFER
PARTICLE INTERACTIONS
PARTICLE KINEMATICS
PARTICLE PROPERTIES
QUANTUM ELECTRODYNAMICS
QUANTUM FIELD THEORY
SCATTERING
T CHANNEL
UNITARITY