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Register a new userMass spectrum and strong decays of tetraquark $bar cbar s qq$ states
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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.
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We have systematically investigated the mass spectrum and rearrangement decay properties of the exotic tetraquark states with four different flavors using a color-magnetic interaction model. Their masses are estimated by assuming that the $X(4140)$ is a $csbar{c}bar{s}$ tetraquark state and their decay widths are obtained by assuming that the Hamiltonian for decay is a constant. According to the adopted method, we find that the most stable states are probably the isoscalar $bsbar{u}bar{d}$ and $csbar{u}bar{d}$ with $J^P=0^+$ and $1^+$. The width for most unstable tetraquarks is about tens of MeVs, but that for unstable $cubar{s}bar{d}$ and $csbar{u}bar{d}$ can be around 100 MeV. For the $X(5568)$, our method cannot give consistent mass and width if it is a $bubar{s}bar{d}$ tetraquark state. For the $I(J^P)=0(0^+),0(1^+)$ double-heavy $T_{bc}=bcbar{u}bar{d}$ states, their widths can be several MeVs.
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 weak decays of the axial-vector tetraquark $T_{bb;bar{u} bar{d}}^{-}$ to the scalar state $Z_{bc;bar{u} bar{d}}^{0}$ are investigated using the QCD three-point sum rule approach. In order to explore the process $T_{bb; bar{u} bar{d}}^{-} to Z_{bc;bar{u} bar{d}}^{0}l bar{ u_l}$, we recalculate the spectroscopic parameters of the tetraquark $T_{bb;bar{u} bar{d}}^{-}$ and find the mass and coupling of the scalar four-quark system $Z_{bc;bar{u} bar{d}}^{0}$, which are important ingredients of calculations. The spectroscopic parameters of these tetraquarks are computed in the framework of the QCD two-point sum rule method by taking into account various condensates up to dimension ten. The mass of the $T_{bb;bar{u} bar{ d}}^{-}$ state is found to be $m=(10035~pm 260)~mathrm{MeV}$, which demonstrates that it is stable against the strong and electromagnetic decays. The full width $Gamma$ and mean lifetime $tau$ of $T_{bb;bar{u} bar{d} }^{-}$ are evaluated using its semileptonic decay channels $T_{bb; bar{u} bar{d}}^{-} to Z_{bc;bar{u} bar{d}}^{0}l bar{ u_l}$, $l=e,mu$ and $tau$. The obtained results, $Gamma=(7.17pm 1.23)times 10^{-8 } mathrm{MeV}$ and $tau =9.18_{-1.34}^{+1.90}~mathrm{fs}$, can be useful for experimental investigations of the doubly-heavy tetraquarks.
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.
In this work, we study systematically the mass splittings of the $qqbar{Q}bar{Q}$ ($q=u$, $d$, $s$ and $Q=c$, $b$) tetraquark states with the color-magnetic interaction by considering color mixing effects and estimate roughly their masses. We find that the color mixing effect is relatively important for the $J^P=0^+$ states and possible stable tetraquarks exist in the $nnbar{Q}bar{Q}$ ($n=u$, $d$) and $nsbar{Q}bar{Q}$ systems either with $J=0$ or with $J=1$. Possible decay patterns of the tetraquarks are briefly discussed.
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