QCD sum rule study of hidden-charm pentaquarks

Abstract

We study the mass spectra of hidden-charm pentaquarks having spin J = We systematically construct all the relevant local hiddencharm pentaquark currents, and we select some of them to perform QCD sum rule analyses. We find that the P c (4380) and P c (4450) can be identified as hidden-charm pentaquark states composed of an anti-charmed meson and a charmed baryon. Besides them, we also find (a) the lowest-lying hidden-charm pentaquark state of J P = 1/2 − has the mass 4.33 +0.17 −0.13 GeV, while the one of J P = 1/2 + is significantly higher, that is, around 4.7-4.9 GeV; (b) the lowest-lying hidden-charm pentaquark state of J P = 3/2 − has the mass 4.37 +0.18 −0.13 GeV, consistent with the P c (4380) of J P = 3/2 − , while the one of J P = 3/2 + is also significantly higher, that is, above 4.6 GeV; (c) the hidden-charm pentaquark state of J P = 5/2 − has a mass around 4.5-4.6 GeV, slightly larger than the P c (4450) of J P = 5/2 + .

The hidden-charm pentaquark and tetraquark states

“…Their possible decay modes were also discussed. The same approach was used to systematically study hidden-charm pentaquarks of spins J = 1 2 / 3 2 / 5 2 [331], where a full classification of the local hidden-charm pentaquark interpolating currents is given.…”

“…[330,331], Wang applied the method of QCD sum rule to study the hidden-charm pentaquarks P c (4380) and P c (4450), but used the diquark-diquark-antiquark type interpolating currents [346,347] ilac…”

“…[330,331] based on the results of Refs. [332,333,334,335,336,337,338,339,340,341,36,342,343,344,345] which studied light baryon, tetraquark and dibaryon currents.…”

“…The first one η ccuud couples well to the combination ofD * and Σ c . These different internal structures suggest that the choice of currents could be important when applying the method of QCD sum rule to study multiquark states, in which cases there always exist many currents of different color, flavor, orbit and spin structures [331]. For example, if one wants to study a physical pentaquark state of the molecular type, it would be best to choose an interpolating current also of the molecular type to ensure a large overlap with that state.…”

“…[331]), despite of their different internal structures. The color rearrangement for pentaquarks was given in Ref.…”