arXiv:0705.2632·v3·High Energy Physics — Theory

Dynamics of Baryons from String Theory and Vector Dominance

Deog Ki Hong🇰🇷 · Mannque Rho🇫🇷 · Ho-Ung Yee🇰🇷 · Piljin Yi🇰🇷

We consider a holographic model of QCD from string theory, a la Sakai and Sugimoto, and study baryons. In this model, mesons are collectively realized as a five-dimensional \$U(N_F)=U(1)\times SU(N_F) $Y an g - M i l l s f i e l d an d ba r y o n s a r ec l a ss i c a l l y i d e n t i f i e d a s$ SU(N_F) $so l i t o n s w i t ha u ni tP o n t r y a g inn u mb er an d$ N_c $e l ec t r i cc ha r g es . T h eso l i t o ni ss h o w n t o b e v er y s ma l l in t h e l a r g e^{'} t H oo f t co u pl in g l imi t, a l l o w in g u s t o in t r o d u ce an e f f ec t i v e f i e l d$ {\cal B} $. I t sco u pl in g t o t h e m eso n s a r e d i c t a t e d b y t h eso l i t o n s t r u c t u r e, an d co n s i s t so f a d i r ec t ma g n e t i cco u pl in g t o t h e$ SU(N_F) $f i e l d s t r e n g t ha s w e l l a s aminima l co u pl in g t o t h e$ U(N_F) $g a ug e f i e l d . U p o n t h e d im e n s i o na l r e d u c t i o n, t hi se f f ec t i v e a c t i o n r e p r o d u ces a l l in t er a c t i o n t er m s b e tw ee nn u c l eo n s an d anin f ini t e t o w er o f m eso n s inamann er co n s i s t e n tw i t h t h e l a r g e$ N_c$ expansion. We further find that all electromagnetic interactions, as inferred from the same effective action via a holographic prescription, are mediated by an infinite tower of vector mesons, rendering the baryon electromagnetic form factors completely vector-dominated as well. We estimate nucleon-meson couplings and also the anomalous magnetic moments, which compare well with nature.

Comments: 65pages, 3 figures, vector mesons and axial-vector mesons are now canonically normalized (comparisons with data and conclusions unaffected)

Dynamics of Baryons from String Theory and Vector Dominance

Abstract

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