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Register a new userFully-strange tetraquark $ssbar{s}bar{s}$ spectrum and possible experimental evidence
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In this work we construct 36 tetraquark configurations for the $1S$-, $1P$-, and $2S$-wave states, and make a prediction of the mass spectrum for the tetraquark $ssbar{s}bar{s}$ system in the framework of a nonrelativistic potential quark model without the diquark-antidiquark approximation. The model parameters are well determined by our previous study of the strangeonium spectrum. We find that the resonances $f_0(2200)$ and $f_2(2340)$ may favor the assignments of ground states $T_{(ssbar{s}bar{s})0^{++}}(2218)$ and $T_{(ssbar{s}bar{s})2^{++}}(2378)$, respectively, and the newly observed $X(2500)$ at BESIII may be a candidate of the lowest mass $1P$-wave $0^{-+}$ state $T_{(ssbar{s}bar{s})0^{-+}}(2481)$. Signals for the other $0^{++}$ ground state $T_{(ssbar{s}bar{s})0^{++}}(2440)$ may also have been observed in the $phiphi$ invariant mass spectrum in $J/psitogammaphiphi$ at BESIII. The masses of the $J^{PC}=1^{--}$ $T_{ssbar{s}bar{s}}$ states are predicted to be in the range of $sim 2.44-2.99$ GeV, which indicates that the $phi(2170)$ resonance may not be a good candidate of the $T_{ssbar{s}bar{s}}$ state. This study may provide a useful guidance for searching for the $T_{ssbar{s}bar{s}}$ states in experiments.
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We systematically study the mass spectrum and strong decays of the S-wave $bar cbar s q q$ states in the compact tetraquark scenario with the quark model. The key ingredients of the model are the Coulomb, the linear confinement, and the hyperfine interactions. The hyperfine potential leads to the mixing between different color configurations, as well as the large mass splitting between the two ground states with $I(J^P)=0(0^+)$ and $I(J^P)=1(0^+)$. We calculate their strong decay amplitudes into the $bar D^{(*)}K^{(*)}$ channels with the wave functions from the mass spectrum calculation and the quark interchange method. We examine the interpretation of the recently observed $X_0(2900)$ as a tetraquark state. The mass and decay width of the $I(J^P)=1(0^+)$ state are $M=2941$ MeV and $Gamma_X=26.6$ MeV, respectively, which indicates that it might be a good candidate for the $X_0(2900)$. Meanwhile, we also obtain an isospin partner state $I(J^P)=0(0^+)$ with $M=2649$ MeV and $Gamma_{Xrightarrow bar D K}=48.1$ MeV, respectively. Future experimental search for $X(2649)$ will be very helpful.
We have studied the masses for fully open-flavor tetraquark states $bcbar{q}bar{s}$ and $scbar{q}bar{b}$ with quantum numbers $J^{P}=0^{+},1^{+}$. We systematically construct all diquark-antiquark interpolating currents and calculate the two-point correlation functions and spectral densities in the framework of QCD sum rule method. Our calculations show that the masses are about $7.1-7.2$ GeV for the $bcbar{q}bar{s}$ tetraquark states and $7.0-7.1$ GeV for the $scbar{q}bar{b}$ tetraquarks. The masses of $bcbar{q}bar{s}$ tetraquarks are below the thresholds of $bar{B}_{s}D$ and $bar{B}_{s}^{*}D$ final states for the scalar and axial-vector channels respectively. The $scbar{q}bar{b}$ tetraquark states with $J^{P}=1^{+}$ lie below the $B_{c}^{+}K^{*}$ and $B_{s}^{*}D$ thresholds. Such low masses for these possible tetraquark states indicate that they can only decay via weak interaction and thus are very narrow and stable.
The mass and coupling of the doubly charmed $J^P=0^{-}$ diquark-antidiquark states $T_{cc;bar{s} bar{s}}^{++}$ and $T_{cc;bar{d} bar{s}}^{++}$ that bear two units of the electric charge are calculated by means of QCD two-point sum rule method. Computations are carried out by taking into account vacuum condensates up to and including terms of tenth dimension. The dominant $S$-wave decays of these tetraquarks to a pair of conventional $ D_{s}^{+}D_{s0}^{ast +}(2317)$ and $D^{+}D_{s0}^{ast +}(2317)$ mesons are explored using QCD three-point sum rule approach, and their widths are found. The obtained results $m_{T}=(4390~pm 150)~mathrm{MeV}$ and $Gamma =(302 pm 113~mathrm{MeV}$) for the mass and width of the state $T_{cc;bar{ s} bar{s}}^{++}$, as well as spectroscopic parameters $widetilde{m} _{T}=(4265pm 140)~mathrm{MeV}$ and $widetilde{Gamma }=(171~pm 52)~ mathrm{MeV}$ of the tetraquark $T_{cc;bar{d} bar{s}}^{++}$ may be useful in experimental studies of exotic resonances.
The new members of the charm-strange family $D_{sJ}^{*}(2317)$, $D_{sJ}(2460)$ and $D_s(2632)$, which have the surprising properties, are challenging the present models. Many theoretical interpretations have been devoted to this issue. Most of authors suggest that they are not the conventional $cbar s$ quark model states, but possibly are four-quark states, molecule states or mixtures of a P-wave $cbar s$ and a four-quark state. In this work, we follow the four-quark-state picture, and study the masses of $cnbar nbar s/csbar sbar s$ states ($n$ is $u$ or $d$ quark) in the chiral SU(3) quark model. The numerical results show that the mass of the mixed four-quark state ($cnbar nbar s/csbar sbar s$) with spin parity $J^P=0^{+}$ might not be $D_s(2632)$. At the same time, we also conclude that $D_{sJ}^{*}(2317)$ and $D_{sJ}(2460)$ cannot be explained as the pure four-quark state.
Inspired by the recent observation of $chi_{c0}(3930)$, $X(4685)$ and $X(4630)$ by the LHCb Collaboration and some exotic resonances such as $X(4350)$, $X(4500)$, etc. by several experiment collaborations, the $csbar{c}bar{s}$ tetraquark systems with $IJ^{P}=00^+$, $01^+$ and $02^+$ are systematically investigated in the framework of the quark delocalization color screening model(QDCSM). Two structures, the meson-meson and diquark-antidiquark structures, as well as the channel-coupling of all channels of these two configurations are considered in this work. The numerical results indicate that the molecular bound state $bar{D}_{s}D_{s}$ with $IJ^{P}=00^+$ can be supposed to explain the $chi_{c0}(3930)$. Besides, by using the stabilization method, several resonant states are obtained. There are four $IJ^{P}=00^{+}$ states around the resonance mass 4035 MeV, 4385 MeV, 4524 MeV, and 4632 MeV, respectively; one $IJ^{P}=01^{+}$ state around the resonance mass 4327 MeV; and two $IJ^{P}=02^{+}$ states around the resonance mass 4419 MeV and 4526 MeV, respectively. All of them are compact tetraquarks. Among these states, $X(4350)$, $X(4500)$ and $X(4700)$ can be explained as the compact tetraquark state with $IJ^{P}=00^{+}$, and the $X(4274)$ is possible to be a candidate of the compact tetraquark state with $IJ^{P}=01^{+}$. More experimental tests are expected to check the existence of all these possible resonance states.
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