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Register a new userFull-heavy tetraquark states and their evidences in the LHCb di-$J/psi$ spectrum
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In the framework of a nonrelativistic potential quark model (NRPQM) for heavy quark system, we investigate the mass spectrum of the $P$-wave tetraquark states of $ccbar{c}bar{c}$ and $bbbar{b}bar{b}$. The Hamiltonian contains a linear confinement potential and parameterized one-gluon-exchange potential which includes a Coulomb type potential and spin-dependent potentials. The full-heavy tetraquark system is solved by a harmonic oscillator expansion method. With the same parameters fixed by the charmonium and bottomonium spectra, we obtained the full spectra for the $S$ and $P$-wave heavy tetraquark states. We find that the narrow structure around 6.9 GeV recently observed at LHCb in the di-$J/psi$ invariant mass spectrum can be naturally explained by the $P$-wave $ccbar{c}bar{c}$ states. Meanwhile, the observed broad structure around $6.2sim 6.8$ GeV can be consistently explained by the $S$-wave states around 6.5 GeV predicted in our previous work. Some contributions from those suppressed low-lying $P$-wave states around 6.7 GeV are also possible. Other decay channels are implied in such a scenario and they can be investigated by future experimental analysis. Considering the large discovery potential at LHCb, we give our predictions of the $P$-wave $bbbar{b}bar{b}$ states which can be searched for in the future.
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Partial wave analysis is performed, with effective potentials as dynamical inputs, to scrutinize the recent LHCb data on the di-$J/psi$ invariant mass spectrum. Coupled-channel effects are incorporated in the production amplitude via final state interactions. The LHCb data can be well described. A dynamical generated pole structure, which can be identified as the $X(6900)$ state, is found. Our analysis also provides hints for the existence of three other possible states: a bound state $X(6200)$, a broad resonant state $X(6680)$ and a narrow resonant state $X(7200)$. The $J^{PC}$ quantum numbers of the $X(6680)$ and $X(6900)$ states should be $2^{++}$, while the $X(6200)$ and $X(7200)$ states prefer $0^{++}$. To determine the above states more precisely, more experimental data for the channels, such as $J/psipsi(2S)$, $J/psipsi(3770)$, di-$psi(2S)$, are required.
Motivated by a recent successful dynamical explanation for the newly observed fully-charm structure $X(6900)$ in the mass spectrum of di-$J/psi$ by LHCb [J.~Z.~Wang textit{et al.} arXiv:2008.07430], in this work, we extend the same dynamical rescattering mechanism to predict the line shape of more potential fully-heavy structures in the invariant mass spectrum of $J/psi psi(3686)$, $J/psi psi(3770)$, $psi(3686) psi(3686)$, and $J/psi Upsilon(1S)$ at high energy proton-proton collisions, whose verification in experiments should be helpful to further clarify the nature of $X(6900)$. The above final states of vector heavy quarkonia can be experimentally reconstructed more effectively by a $mu^+mu^-$ pair in the muon detector compared with $Qbar{Q}$ meson with other quantum numbers. Furthermore, the corresponding peak mass positions of each of predicted fully-heavy structures are also given. Our theoretical studies here could provide some valuable information for the future measurement proposals of LHCb and CMS, especially based on the accumulated data after completing Run III of LHC in the near future.
The two exotic $P_c^+(4380)$ and $P_c^+(4450)$ discovered in $2015$ by the LHCb Collaboration, together with the four resonances $X(4140)$, $X(4274)$, $X(4500)$ and $X(4700)$, reported in $2016$ by the same collaboration, are described in a constituent quark model which has been able to explain the properties of charmonium states from the $J/psi$ to the $X(3872)$. Using this model we found a $bar DSigma_c^*$ bound state with $J^P=frac{3}{2}^-$ that may be identified with the $P_c^+(4380)$. In the $bar D^*Sigma_c$ channel we found three possible candidates for the $P_c^+(4450)$ with $J^P=frac{1}{2}^-$, $frac{3}{2}^-$ and $frac{3}{2}^+$ with almost degenerated energies. The $X(4140)$ resonance appears as a cusp in the $J/psiphi$ channel due to the near coincidence of the $D_{s}^{pm}D_{s}^{astpm}$ and $J/psiphi$ mass thresholds. The remaining three $X(4274)$, $X(4500)$ and $X(4700)$ resonances appear as conventional charmonium states with quantum numbers $3^{3}P_{1}$, $4^{3}P_{0}$ and $5^{3}P_{0}$, respectively; and whose masses and widths are slightly modified due to their coupling with the corresponding closest meson-meson thresholds.
Structure in the di-$J/psi$ mass spectrum observed by the LHCb experiment around 6.9 and 7.2 GeV is interpreted in terms of $J^{PC}=0^{++}$ and $2^{++}$ resonances between a $cc$ diquark and a $bar c bar c$ antidiquark, using a recently confirmed string-junction picture to calculate tetraquark masses. The main peak around 6.9 GeV is likely dominated by the $0^{++}(2S)$ state, a radial excitation of the $cc$-$bar c bar c$ tetraquark, which we predict at $6.871pm 0.025$ GeV. The dip around 6.75 GeV is ascribed to the opening of the Swave di-$chi_{c0}$ channel, while the dip around 7.2 GeV could be correlated with the opening of the di-$eta_c(2S)$ or $Xi_{cc} bar Xi_{cc}$ channel. The low-mass part of the di-$J/psi$ structure appears to require a broad resonance consistent with a predicted $2^{++}(1S)$ state with invariant mass around $M_{rm inv} = 6400$ MeV. Implications for $bb bar b bar b$ tetraquarks are discussed.
We use the Laplace/Borel sum rules (LSR) and the finite energy/local duality sum rules (FESR) to investigate the non-strange $udbar ubar d$ and hidden-strange $usbar ubar s$ tetraquark states with exotic quantum numbers $J^{PC}=0^{+-}$ . We systematically construct all eight possible tetraquark currents in this channel without covariant derivative operator. Our analyses show that the $udbar ubar d$ systems have good behaviour of sum rule stability and expansion series convergence in both the LSR and FESR analyses, while the LSR for the $usbar ubar s$ states do not associate with convergent OPE series in the stability regions and only the FESR can provide valid results. We give the mass predictions $1.43pm0.09$ GeV and $1.54pm0.12$ GeV for the $udbar ubar d$ and $usbar ubar s$ tetraquark states, respectively. Our results indicate that the $0^{+-}$ isovector $usbar ubar s$ tetraquark may only decay via weak interaction mechanism, e.g. $X_{usbar{u}bar{s}}to Kpipi$, since its strong decays are forbidden by kinematics and the symmetry constraints on the exotic quantum numbers. It is predicted to be very narrow, if it does exist. The $0^{+-}$ isoscalar $usbar ubar s$ tetraquark is also predicted to be not very wide because its dominate decay mode $X_{usbar{u}bar{s}}tophipipi$ is in $P$-wave.
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