Masses of orbitally excited baryons in large Nc QCD

Abstract

We present the first phenomenological study of the masses of orbitally excited baryons in large N c QCD. Restricting here to the nonstrange sector of the ℓ = 1 baryons, the 1/N c expansion is used to order and select a basis of effective operators that spans the nine observables (seven masses and two mixing angles). Fits are performed using subsets of the complete set of nine operators, including corrections up to O(1/N c ) where leading order is N 1 c .This study shows that the 1/N c expansion provides an excellent framework for analyzing the mass spectrum, and uncovers a new hierarchy of operator contributions.

Decays of nonstrange negative parity baryons in the1/Ncexpansion

“…In the sector of ground state baryons (identified for N c = 3 with the spin 1/2 octet and spin 3/2 decuplet in the case of three flavors), that symmetry gives rise to several important relations that hold at different orders in the 1/N c expansion [3,4,5]. The domain of excited baryons (baryon resonances) has also been explored in the framework of the 1/N c expansion [6,7,8,9,10,11,12,13,14] with very promising results. The analyses carried out so far have been constrained to states that belong to a definite spin-flavor and orbital multiplet, i.e.…”

Excited heavy baryons and their symmetries I: Formalism

“…These analyses have been extended to orbitally excited baryons in Refs. [28][29][30][31], although orbitally excited baryons containing charm or bottom quarks were only briefly discussed.…”

Excited Baryons in Large Nc QCD

“…[ 17,18,19,20,21,22,23,24]. On the one hand, as noted above, there is no real a priori justification for the approach.…”

“…If the states are fixed by symmetry and the symmetry can be simply encoded in a quark model basis it seems that one can simply create a large N c quark model and automatically get the large N c results. In fact, a number of papers have done just that [ 16,17,18,19,20,21,22,23,24]. There are two conceptual problems associated with this, however.…”

“…This provides some a posteriori justification for the treatments of refs. [ 16,17,18,19,20,21,22,23,24].…”