Observation of a Narrow Pentaquark State, Pc(4312)+ , and of the Two-Peak Structure of the

R. Aaij¹,

C. Abellán Beteta²,

B. Adeva³

et al.

Abstract

A narrow pentaquark state, P c ð4312Þ þ , decaying to J=ψp, is discovered with a statistical significance of 7.3σ in a data sample of Λ 0 b → J=ψpK − decays, which is an order of magnitude larger than that previously analyzed by the LHCb Collaboration. The P c ð4450Þ þ pentaquark structure formerly reported by LHCb is confirmed and observed to consist of two narrow overlapping peaks, P c ð4440Þ þ and P c ð4457Þ þ , where the statistical significance of this two-peak interpretation is 5.4σ. The proximity of the Σ þ cD 0 and Σ þ cD Ã0 thresholds to the observed narrow peaks suggests that they play an important role in the dynamics of these states.

Doubly charmed pentaquarks

“…By a mass shift with respect to Σ c D, according to previous discussion, the obtained resonance state is Σ c D(4446) with a very small width of Γ = 2.2 MeV. As one can elucidate from our discussion until now is that the doubly-charmed pentaquark states present similar features than those hidden-charm ones observed experimentally, P + c (4312), P + c (4440) and P + c (4457) [1], which are mainly explained as molecular states of Σ We expect that, in the near future, the potential molecular candidates in the doubly-charm sector, Σ c D(4431) and Σ c D(4446), being confirmed experimentally.…”

“…During the past 15 years, more than two dozens of nontraditional charmonium-and bottomonium-like states, the so-called XYZ mesons, have been observed at Bfactories (BaBar, Belle and CLEO), τ -charm facilities (CLEO-c and BESIII) and also proton-(anti)proton colliders (CDF, D0, LHCb, ATLAS and CMS). Among all of them, one can highlight the new three hiddencharm pentaquark candidates observed in 2019 by the LHCb Collaboration [1] in the J/ψp invariant mass spectrum of Λ 0 b → J/ψK − p decays, they are signed as P c (4312) + , P c (4440) + and P c (4457) + , respectively. The story of hidden-charm pentaquark states can actually be dated back to 2015, when two exotic signals: P c (4380) + and P c (4450) + , were announced by the same collaboration [2].…”

Pentaquark components in low-lying baryon resonances

“…The predicted values of 4483 and 4495 MeV for the lowest hidden-charm pentaquark in the [21] lying below the threshold of a single bottom baryon and B(B * ) mesons, which is consistent with other work [40]. The newly observed P c states by the LHCb collaboration have been largely interpreted as hadronic molecule states since there are abundant charmed meson and charmed baryon thresholds available [26]. Within the molecular scenario, the mass spectrum [27][28][29][30][31][32][33][34][35][36][37][38][39][40] and dynamical properties [35][36][37][38][39][40] have been successfully explained in various methods.…”

“…In this constituent quark model with a color dependent Cornell-like potential, however, we have given not only the possible theoretical interpretations for N (1895)1/2 − , N (1875)3/2 − , ∆(1900)1/2 − , and ∆(1940)3/2 − states as negative-parity partners of the well known nucleon and ∆ resonances, but also effectively solved the long-standing ordering problem of N (1440), N (1520) and N (1535) by mixing the q 3 and q 4q components. Motivated by the hidden-charm pentaquark candidates recently found by the LHCb Collaboration [26] we also calculate the mass spectra of hidden heavy pentaquarks of q 3 QQ systems. The quark configurations and wave functions of the q 3 QQ systems are derived in Appendix B.…”

Recently observed Pc as molecular states and possible mixture of Pc(4457)

“…Indeed, with the limited informations in [21] we can not trace P c (4457) for now. We expect that LHCb can further investigate quantum numbers and more decay channels, as well as add P c (4457) in their amplitude analysis, to justify our predictions.…”