QCD sum rule study of hidden-charm pentaquarks

We study the mass spectra of hidden-charm pentaquarks having spin J = 1/2/3/2/5/2 and quark contents uudc (c) over bar. We systematically construct all the relevant local hidden-charm 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(-0.13)(+0.17) GeV, while the one of J(P) = 1/2(+) is significantly higher, that is, around 4.7-4.9GeV; (b) the lowest-lying hidden-charm pentaquark state of J(P) = 3/2(-) has the mass 4.37(-0.13)(+0.18) 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 4.6GeV; (c) the hidden-charm pentaquark state of J(P) = 5/2(-) has a mass around 4.5-4.6GeV, slightly larger than the P-c(4450) of J(P) = 5/2(+).