Relativistic effects on the neutron charge form factor in the constituent quark model

Fabio Cardarelli; Silvano Simula

doi:10.1016/S0370-2693(99)01146-6

paper

Relativistic effects on the neutron charge form factor in the constituent quark model

arXiv:nucl-th/9906095 · doi:10.1016/S0370-2693(99)01146-6

Abstract

The neutron charge form factor GEn(Q**2) is investigated within a constituent quark model formulated on the light-front. It is shown that, if the quark initial motion is neglected in the Melosh rotations, the Dirac neutron form factor F1n(Q**2) $r ece i v es a r e l a t i v i s t i ccor r ec t i o n w hi c h c an ce l se x a c tl y a g ain s tt h e F o l d y t er min GE n (Q * * 2), a s i t ha s b ee n r ece n tl y a r g u e d b y I s g u r . M or eo v er, a tt h es am e l e v e l o f a pp r o x ima t i o n t h er a t i oo f t h e p r o t o n t o n e u t r o nma g n e t i c f or m f a c t or s GM p (Q * * 2) / GM n (Q * * 2) i ss t i l l g i v e nb y t h e nai v e S U (6) - sy mm e t r y e x p ec t a t i o n, - 3/2. H o w e v er, i t i s a l sos h o w n t ha tt h e f u l l M e l os h r o t a t i o n s b r e ak S U (6) sy mm e t r y, g i v in g r i se t o GE n (Q * * 2) = /0 an d GM p (Q * * 2) / GM n (Q * * 2) = / - 3/2 e v e n w h e na S U (6) - sy mm e t r i cc an o ni c a l w a v e f u n c t i o ni s a ss u m e d . I tt u r n so u tt ha t r e l a t i v i s t i ce f f ec t s a l o n ec ann o t e x pl ain s im u l t an eo u s l y t h ee x p er im e n t a l d a t a o n GE n (Q * * 2)$ and GMp(Q**2)/GMn(Q**2).

final version with one minor correction and updated references; to appear in Physics Letters B