arXiv subjects

G. C. Gellas

Publications and source records attributed to G. C. Gellas.

3 recordsLinked to original sources

arXiv1999

Chiral symmetry and the Delta-Nucleon transition form factors

The three complex form factors entering the $Δ\to Nγ^\ast$ vertex are calculated to ${\cal O}(ε^3)$ in the framework of a chiral effective theory with explicit Δ(1232) degrees of freedom included. It is shown that the low q^2 behavior of the form factors is governed by $πN$, $πΔ$ loop effects. Predictions are given for the q^2-dependence of the three transition-multipoles $M1(q^2), E2(q^2), C2(q^2)$. Furthermore, the role of presently unknown low energy constants that affect the values of the multipole ratios EMR(q^2) and CMR(q^2) is elucidated.

hep-ph↗

arXiv1998

N Delta - Transition Form Factors at Low Momentum Transfer

The three complex form factors entering the $Δ\to Nγ^\ast$ vertex are calculated to ${\cal O}(ε^3)$ in the framework of a chiral effective theory with explicit $Δ$(1232) degrees of freedom. Furthermore, the role of presently unknown low energy constants that affect the values of EMR and CMR is elucidated.

hep-ph↗

arXiv1997

Worldline approach to Sudakov-type form factors in non-Abelian gauge theories

We calculate Sudakov-type form factors for isolated spin-1/2 particles (fermions) entering non-Abelian gauge-field systems. We consider both the on- and the off-mass-shell case using a methodology which rests on a worldline casting of field theories. The simplicity and utility of our approach derives from the fact that we are in a position to make, a priori, a more transparent separation (factorization), with respect to a given scale, between short- and long-distance physics than diagramatic methods.

hep-ph↗