Physics – High Energy Physics – High Energy Physics - Phenomenology
Scientific paper
2008-03-20
Eur.Phys.J.A36:329-348,2008
Physics
High Energy Physics
High Energy Physics - Phenomenology
20 pages, 5 figures, 2 tables
Scientific paper
10.1140/epja/i2008-10599-0
The covariant spectator formalism is used to model the nucleon and the $\Delta$(1232) as a system of three constituent quarks with their own electromagnetic structure. The definition of the ``fixed-axis'' polarization states for the diquark emitted from the initial state vertex and absorbed into the final state vertex is discussed. The helicity sum over those states is evaluated and seen to be covariant. Using this approach, all four electromagnetic form factors of the nucleon, together with the {\it magnetic} form factor, $G_M^*$, for the $\gamma N \to \Delta$ transition, can be described using manifestly covariant nucleon and $\Delta$ wave functions with {\it zero} orbital angular momentum $L$, but a successful description of $G_M^*$ near $Q^2=0$ requires the addition of a pion cloud term not included in the class of valence quark models considered here. We also show that the pure $S$-wave model gives electric, $G_E^*$, and coulomb, $G^*_C$, transition form factors that are identically zero, showing that these form factors are sensitive to wave function components with $L>0$.
Gross Franz
Pena M. T.
Ramalho G.
No associations
LandOfFree
A Covariant model for the nucleon and the $Δ$ does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with A Covariant model for the nucleon and the $Δ$, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and A Covariant model for the nucleon and the $Δ$ will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-578286