We discuss the possible existence of the fullyheavy tetraquarks. We calculate the ground-state energy of the bbbb bound state, where b stands for the bottom quark, in a nonrelativistic effective field theory framework with onegluon-exchange (OGE) color Coulomb interaction, and in a relativized diquark model characterized by OGE plus a confining potential. Our analysis advocates the existence of uni-flavor heavy four-quark bound states. The ground state bbbb tetraquark mass is predicted to be (18.72 ± 0.02) GeV. Mass inequality relations among the lowest Q QQQ states, where Q ∈ {c, b}, and the corresponding heavy quarkonia are presented, which give the upper limit on the mass of ground state Q QQQ. The possible decays of the lowest bbbb are highlighted, which might provide useful references in the search for them in ongoing LHC experiments, and its width is estimated to be a few tens of MeV.

With Gaussian expansion method (GEM), realistic wave functions are used to calculate coupledchannel effects for the bottomonium under the framework of 3 P 0 model. The simplicity and accuracy of GEM are explained. We calculate the mass shifts, probabilities of the B meson continuum, S − D mixing angles, strong and dielectric decay widths. Our calculation shows that both S − D mixing and the B meson continuum can contribute to the suppression of the vector meson's dielectric decay width. We suggest more precise measurements on the radiative decays of Υ(10580) and Υ(11020) to distinguish these two effects. The above quantities are also calculated with simple harmonic oscillator (SHO) wave function approximation for comparison. The deviation between GEM and SHO indicates that it is essential to treat the wave functions accurately for near threshold states.

We calculate the spectrum of qqcc and sscc tetraquarks, where q, s and c stand for light (u, d), strange and charm quarks, respectively, in a relativized diquark model, characterized by one-gluonexchange (OGE) plus confining potential. In the diquark model, a qqcc (sscc) tetraquark configuration is made up of a heavy-light diquark, qc (sc), and anti-diquark,qc (sc). According to our results, 13 charmonium-like observed states can be accommodated in the tetraquark picture, both in the hidden-charm (qqcc) and hidden-charm hidden-strange (sscc) sectors.

No abstract

No abstract

We propose a new model to create a light meson in the heavy quarkonium transition, which is inspired by the Nambu−Jona-Lasinio (NJL) model. Hadronic transitions of J P C = 1 −− higher charmonia with the emission of an η meson are studied in the framework of the proposed model. The model shows its potential to reproduce the observed decay widths and make predictions for the unobserved channels. We present our predictions for the decay width of Ψ → J/ψη and Ψ → h c (1P )η, where Ψ are higher S and D wave vector charmonia, which provide useful references to search for higher charmonia and determine their properties in forthcoming experiments. The predicted branching fraction B(ψ(4415) → h c (1P )η) = 4.62 × 10 −4 is one order of magnitude smaller than the J/ψη channel. Estimates of partial decay width Γ(Y → J/ψη) are given for Y (4360), Y (4390) and Y (4660) by assuming them as cc bound states with quantum numbers 3 3 D 1 , 3 3 D 1 and 5 3 S 1 , respectively. Our results are in favor of these assignments for Y (4360) and Y (4660). The corresponding experimental data for these Y states has large statistical errors which do not provide any constraint on the mixing angle if we introduce S − D mixing. To identify Y (4390), precise measurements on its hadronic branching fraction are required which are eagerly awaited from BESIII. *

We calculate the probabilities of various charmed meson molecules for X(4260) under the framework of the 3 P 0 model. The results indicate that, even though heavy quark spin symmetry forbids S wave coupling of D 1D to the 3 S 1 charmonia [ψ(nS)], the D wave coupling is allowed and not negligible. Under this symmetry, the D 1D can couple to 3 D 1 charmonia [ψ(nD)] via both S and D waves, and the overall coupling is around three times larger than that of ψ(nS). The X(4260) cannot be a pure molecule but a mixture of a charmonium and various charmed meson components. Since the D 1D couples strongly to ψ(nD), our results suggest that, in the D 1D molecular picture, the charmonium core of X(4260) is ψ(nD) instead of ψ(nS). As a result, the experimental fact that the R ratio has a dip around 4.26 GeV can be understood in the D 1D molecular picture of the X(4260).

We calculate the masses of χ c (3P) states with threshold corrections in a coupled-channel model. The model was recently applied to the description of the properties of χ c (2P) and χ b (3P) multiplets (Ferretti and Santopinto in Phys Lett B 789:550, 2019]. We also compute the open-charm strong decay widths of the χ c (3P) states and their radiative transitions. According to our predictions, the χ c (3P) states should be dominated by the charmonium core, but they may also show small meson-meson components. The X (4274) is interpreted as a cc χ c1 (3P) state. More information on the other members of the χ c (3P) multiplet, as well as a more rigorous analysis of the X (4274)'s decay modes, are needed to provide further indications on the quark structure of the previous resonance.