Mass spectrum of the hidden-charm pentaquarks in the compact diquark model

Abstract

The LHCb collaboration have recently updated their analysis of the resonant J/ψ p mass spectrum in the decay Λ 0 b → J/ψ p K − , making use of their combined Run 1 and Run 2 data. In the updated analysis, three narrow states, P c (4440) + , P c (4457) + , and P c (4312) + , are observed. The spin-parity assignments of these states are not yet known. We interpret these narrow resonances as compact hidden-charm diquark-diquarkantiquark pentaquarks. Using an effective Hamiltonian, based on constituent quarks and diquarks, we calculate the pentaquark mass spectrum for the complete SU (3) F lowest Sand P -wave multiplets, taking into account dominant spin-spin, spin-orbit, orbital and tensor interactions. The resulting spectrum is very rich and we work out the quark flavor compositions, masses, and J P quantum numbers of the pentaquarks. However, heavy quark symmetry restricts the observable states in Λ b -baryon, as well as in the decays of the other weakly-decaying b-baryons, Ξ b and Ω b . In addition, some of the pentaquark states are estimated to lie below the J/ψ p threshold in Λ b -decays (and corresponding thresholds in Ξ b -and Ω b -decays). They decay via cc annihilation into light hadrons or a dilepton pair, and are expected to be narrower than the P c -states observed. We anticipate their discovery, as well as of the other pentaquark states present in the spectrum at the LHC, and in the long-term future at a Tera-Z factory.

Spectrum of the $$uudc \bar{c}$$ hidden charm pentaquark with an SU(4) flavor-spin hyperfine interaction

“…This analysis has been extended in Ref. [15], and presently includes a spin-spin, a spin-orbit and a tensor interaction, obtained from the integration in the color space of the one gluon exchange (OGE) interaction between quarks [16]. The basis contains only the color3 configuration, therefore is smaller than the basis used in the present paper.…”

Spectrum of p -wave hidden-charm exotic mesons in the diquark model

“…We now tabulate matrix elements ∆M of the diquark spin-dependent operators in Eqs. (7) and (16) for the 1P states:…”

“…Alternate constructions of triquark-diquark pentaquarks are studied in Refs. [15,16]. This initial picture has been developed in stages into the dynamical diquark model.…”

Pc(4457)+ , PcCheng1, Liu2 2019Phys. Rev. D960580View full textAdd to dashboardCite

“…Note added.-After the submission of the paper, more studies about the properties of the LHCb pentaquark states appeared [61][62][63][64][65][66][67][68][69][70][71][72][73][74][75]. A number of them discussed the J P assignments of the LHCb pentaquark states.…”

“…In the molecule picture [63][64][65][66][67][68][69][70][71][72], the J P of P c ð4312Þ are always 1=2 − while those of [P c ð4440Þ, P c ð4457Þ] can be ½1=2 − ; 3=2 − , ½3=2 − ; 1=2 − , or ½3=2 − ; 1=2 þ . In the diquark-diquark-antidiquark configuration [73], the J P of P c ð4312Þ can be 3=2 − while those of [P c ð4440Þ, P c ð4457Þ] are ½3=2 þ ; 5=2 þ . A study with QCD sum rule indicates that the lowest ðudcÞ 8 c ðcuÞ 8 c state with mass 4.4 GeV has J P ¼ 1=2 − [75].…”