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تسجيل مستخدم جديدThe possible tetraquark states $cc bar c bar c$ observed by the LHCb experiment
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We give a brief comment on the possible tetraquark states $cc bar c bar c$ observed by the LHCb experiment.
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We have studied the masse spectra for the $ccbar{b}bar{b}$/$bbbar{c}bar{c}$ tetraquark states with quantum numbers $J^{P}=0^{pm},1^{pm}$, and $2^{+}$. We systematically construct the interpolating currents with various spin-parity quantum numbers and
calculate their two-point correlation functions in the framework of QCD moment sum rule method. Our calculations show that the masses are about $12.3-12.4$ GeV for the positive parity $ccbar{b}bar{b}$ tetraquark ground states with $J^{P}=0^+, 1^+, 2^+$, while $12.8-13.1$ GeV for the negative parity channels with $J^{P}=0^-, 1^-$. The mass predictions for the positive parity $ccbar{b}bar{b}$ ground states are lower than the $B_{c}B_{c}$ threshold, implying that these tetraquarks can only decay via weak interaction and thus are expected to be stable and narrow.
We study the existence of fully-heavy hidden-flavor $bcbar{b}bar{c}$ tetraquark states with various $J^{PC}=0^{pm+}, 0^{--},1^{pmpm}, 2^{++}$, by using the moment QCD sum rule method augmented by fundamental inequalities. Using the moment sum rule an
alyses, our calculation shows that the masses for the S-wave positive parity $bcbar{b}bar{c}$ tetraquark states are about $12.2-12.4$ GeV in both $[mathbf{bar{3}_c}]_{bc}otimes[mathbf{3_c}]_{bar{b}bar{c}}$ and $[mathbf{6_c}]_{bc}otimes[mathbf{bar{6}_c}]_{bar{b}bar{c}}$ color configuration channels. Except for two $0^{++}$ states, such results are below the thresholds $T_{eta_ceta_b}/T_{Upsilonpsi}$ and $T_{B_cB_c}$, implying that these S-wave positive parity $bcbar{b}bar{c}$ tetraquark states are probably stable against the strong interaction. For the P-wave negative parity $bcbar{b}bar{c}$ tetraquarks, their masses in the $[mathbf{bar{3}_c}]_{bc}otimes[mathbf{3_c}]_{bar{b}bar{c}}$ channel are around $12.9-13.2$ GeV, while a bit higher in the $[mathbf{6_c}]_{bc}otimes[mathbf{bar{6}_c}]_{bar{b}bar{c}}$ channel. They can decay into the $cbar c+bbar b$ and $cbar b+bbar c$ final states via the spontaneous dissociation mechanism, including the $J/psiUpsilon$, $eta_cUpsilon$, $J/psieta_b$, $B_c^+B_c^-$ channels.
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.
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. Comput
ations 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.
We have calculated the mass spectra for the $bar{D}_s^{(*)}D^{(*)}$ molecular states and $scbar qbar c$ tetraquark states with $J^P=0^+, 1^+, 2^+$. The masses of the axial-vector $bar{D}_sD^{*}$, $bar{D}_s^{*}D$ molecular states and $mathbf{1}_{[sc]}
oplus mathbf{0}_{[bar q bar{c}]}$, $mathbf{0}_{[sc]} oplus mathbf{1}_{[bar q bar{c}]}$ tetraquark states are predicted to be around 3.98 GeV, which are in good agreement with the mass of $Z_{cs}(3985)^-$ from BESIII cite{besiii2020Zcs}. In both the molecular and diquark-antidiquark pictures, our results suggest that there may exist two almost degenerate states, as the strange partners of the $X(3872)$ and $Z_c(3900)$. We propose to carefully examine the $Z_{cs}(3985)$ in future experiments to verify this. One may also search for more hidden-charm four-quark states with strangeness not only in the open-charm $bar{D}_s^{(*)}D^{(*)}$ channels, but also in the hidden-charm channels $eta_c K/K^ast$, $J/psi K/K^ast$.
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