Second order formalism for spin (1/2) fermions and Compton scattering

Journal Article · Fri Apr 01 00:00:00 EDT 2011 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PHYSREVD.83.073001· OSTI ID:21537695

Delgado-Acosta, E G; Napsuciale, Mauro; Rodriguez, Simon ^[1]

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1. Departamento de Fisica, Universidad de Guanajuato, Lomas del Bosque 103, Fraccionamiento Lomas del Campestre, C.P. 37150, Leon, Guanajuato (Mexico)

We develop a second order formalism for massive spin 1/2 fermions based on the projection over Poincare invariant subspaces in the ((1/2),0)+(0,(1/2)) representation of the homogeneous Lorentz group. Using the U(1){sub em} gauge principle we obtain a second order description for the electromagnetic interactions of a spin 1/2 fermion with two free parameters, the gyromagnetic factor g and a parameter {xi} related to odd-parity Lorentz structures. We calculate Compton scattering in this formalism. In the particular case g=2, {xi}=0, and for states with well-defined parity, we recover Dirac results. In general, we find the correct classical limit and a finite value r{sub c}{sup 2} for the forward differential cross section, independent of the photon energy and of the value of the parameters g and {xi}. The differential cross section vanishes at high energies for all g, {xi} except in the forward direction. The total cross section at high energies vanishes only for g=2, {xi}=0. We argue that this formalism is more convenient than Dirac theory in the description of low energy electromagnetic properties of baryons and illustrate the point with the proton case.

• OSTI ID: 21537695
• Journal Information: Physical Review. D, Particles Fields, Vol. 83, Issue 7; Other Information: DOI: 10.1103/PhysRevD.83.073001; (c) 2011 American Institute of Physics; ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
COMPTON EFFECT
DIFFERENTIAL CROSS SECTIONS
FERMIONS
LORENTZ GROUPS
PARITY
POINCARE GROUPS
PROTONS
SCATTERING
SPIN
TOTAL CROSS SECTIONS
ANGULAR MOMENTUM
BARYONS
BASIC INTERACTIONS
CROSS SECTIONS
ELASTIC SCATTERING
ELECTROMAGNETIC INTERACTIONS
ELEMENTARY PARTICLES
HADRONS
INTERACTIONS
LIE GROUPS
NUCLEONS
PARTICLE PROPERTIES
SYMMETRY GROUPS