Mixing of pentaquark and molecular states

Abstract

There are experimental evidences for the existence of narrow states Θ + and Θ c with the same quantum numbers of uudds and uuddc pentaquarks and also N K ( * ) and N D ( * ) molecular states.Their masses deviate from many theoretical estimates of the pure pentaquark and molecular states.In this work we study the possibility that the observed Θ + and Θ c are mixtures of pure pentaquark and molecular states. The mixing parameters are in general related to non-perturbative QCD which are not calculable at present. We determine them by fitting data from known states and then generalize the mechanism to Θ b to predict its mass and width. The mixing mechanism can also naturally explain the narrow width for Θ + and Θ c through destructive interferences, even if the pure pentaquark and molecular states have much larger decay widths. We also briefly discuss the properties of the partner eigenstates of Θ + and Θ c and the possibility of experimentally observe them. Moreover, probable consequences of multi-state mixing are also addressed.

Λc(2940)+: a possible molecular state?

“…We find that one particle exchange model can indeed achieve this. In this model one deduces the effective potential of D * 0 p system by using the linear σ model [15]. Following the standard procedures [16], we calculated the transition matrix element of the elastic scattering D * 0 + p → D * 0 + p in the momentum space by regular quantum field theory method, and then setting q 0 = 0 where q 0 is the 0-th component of the momentum of the exchanged hadrons which possess appropriate quantum numbers, a Fourier transformation from the momentum space to the configuration space is then carried out to obtain the potential.…”

“…The known couplings are given by g N N π = 13.5, [15,19]. The values of the couplings (2520) and g N D * Σc(2520) are not known.…”

“…We have carried out an calculation similar to that in [15] by taking exchanges of π, ω and ρ mesons as the leading interaction of D * 0 and p which eventually binds D * 0 and p into a molecular state, to obtain the binding energy. In the derivation of the effective interaction in the momentum space, to compensate the off-shell effects for the exchanging mesons, one usually phenomenologically introduces a form factor at each effective vertex.…”

“…where P, V are pseudoscalar and vector mesons D, D * . The known couplings are given by g N N π = 13.5, g N N ρ = 3.25, g D * D * ρ = 2.9, g D * Dπ = 18, g D * Dρ = 4.71 GeV −1 and g D * D * π = g D * D * σ = 3.5[15,19]. The values of the couplings g N D * Λ + c (2285) , g N DΣc(2455) , g N D * Σc(2455) , g N DΣc(2520) and g N D * Σc(2520) are not known.…”

Dynamical study of $ud\bar{s}\bar{s}$ in the chiral constituent quark model

“…In [28], Stancu pointed out that there would be a compact tetraquark structure at short range and a molecular structure at medium or large range inside the c cs s system for a more realistic interpretation of Y(4140) reported by the CDF collaboration [29]. The mixture of pure pentaquark and molecular states was also discussed by He et al [30] to investigate the properties of possible exotic baryons + and c . Due to the complication of the few-body system calculation, apart from a rough discussion in our previous work [31], so far, no one has studied the effects of mixture between diquark-antidiquark and molecular structures for the ud s s system at quark level.…”