How and when can one identify hadronic molecules in the baryon spectrum⋆

Abstract

Abstract. A method to identify hadronic molecules in the particle spectrum is reviewed and the conditions for its applicability discussed. Special emphasis is put on the discussion of molecule candidates in the baryon spectrum.PACS. PACS-key discribing text of that key -PACS-key discribing text of that key

Constraint onKK¯compositeness of thea0(980)andSekihara1, Kumano2 2015Phys. Rev. D

“…It is remarkable that two thirds of the combinations of the Flatte parameter sets reproduce the experimental value with the errors (28) while only four combinations exceed the experimental upper limit of the mixing intensity (29). We also note that some of the parameter sets tend to lead to small or large mixing intensity.…”

“…Table I with the errors for the KK coupling constants. The central value of the mixing intensity is shown in bold when it is consistent with the experimental value (28), in italic when out of the experimental errors, and with underline when above the upper limit (29 In the chiral unitary approach, we solve the BetheSalpeter equation in an algebraic form so as to obtain a scattering amplitude of two pseudoscalar mesons…”

“…We then discuss the compositeness of the scalar mesons with the experimental value of the mixing intensity (28) and (29), which was obtained as the ratio of two branching fractions of J/ψ, J/ψ → φf 0 (980) → φa 0 (980) → φπη to J/ψ → φf 0 (980) → φππ. This experimental value, together with the upper limit of |X a X f | for each value of the mixing intensity ξ f a shown in Fig.…”

“…In Fig. 6 the shaded area corresponds to the allowed region within the experimental value (28) including errors, and the solid line to the upper limit from the experimental value (29), ξ f a = 1.1%. The region above the solid line in Fig.…”

“…[28] the experimental value of the mixing intensity was compared to several theoretical predictions and structure of the two resonances was discussed. We here emphasize that coupling constants of a 0 (980)-KK and f 0 (980)-KK reflect the KK structure of the a 0 (980) and f 0 (980) resonances, respectively; especially a larger KK coupling constant means a larger fraction of the KK component in the scalar mesons [29]. In recent studies this statement has been formulated in terms of compositeness [30][31][32][33][34][35][36] in the so-called chiral unitary approach, which is a way to combine the chiral perturbation theory and the scattering unitarity.…”