Dynamics of pentaquarks in constituent quark models: recent developments

Abstract

Abstract. Some recent developments in the study of light and heavy pentaquarks are reviewed, mainly within constituent quark models. Emphasis is made on results obtained in the flavor-spin model where a nearly ideal octet-antidecuplet mixing is obtained. The charmed antisextet is reviewed in the context of an SU(4) classification.

QCD sum rules for the anticharmed pentaquark

“…We find a convergent Operator Product Expansion (OPE) only for the non-strange heavy pentaquark sum rule obtained with an interpolating field composed of two diquarks and one anti-charm quark, that has been previously used by us [34]. The stability of non-strange heavy pentaquark is consistent with the result based on the quark model with flavor spin interaction [25]. We then refine the convergent sum rule by explicitly including the DN two-particle irreducible contribution.…”

“…The question is whether such strong diquark structure will survive other non-perturbative QCD dynamics in a multiquark environment and produce a stable pentaquark state. Such questions are being intensively pursued in quark model approaches [24][25][26]. In particular, an important question at hand is whether the net attraction from the diquark correlations in the pentaquark configuration is stronger than that from the corresponding diquark and additional quark-antiquark correlation present when the pentaquark separates into a nucleon and a meson state.…”

Charmed exotics in heavy ion collisions

“…The attraction to form a meson becomes smaller if the s is replaced by either a c or b. Full constituent quark model calculations [19,20] indeed find a possible stable heavy pentaquark baryon. A likely pentaquark structure would be that suggested in Ref.…”

“…The excitation energy of a diquark in a L = 1 state, ∆E L=1 , can be estimated by approximating the charmed baryon as a sum of a charm quark and a diquark, because the interaction between them is small in the heavy quark limit. Attributing the mass difference between the parity doublet partners of the posi- [19,20,22] and the QCD sum-rules study [23] in which a possible stable heavy pentaquark baryon has been found. For a pair of ud and us diquarks in Θ cs (udusc), they do not have to be in the L = 1 state, and hence there is no additional contribution from the orbital energy [24].…”