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Register a new userMass spectra of doubly heavy tetraquarks in an improved chromomagnetic interaction model
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Doubly heavy tetraquark $(QQbar qbar q)$ states are the prime candidates of tightly bound exotic systems and weakly decaying. In the framework of the improved chromomagnetic interaction (ICMI) model, we complete a systematic study on the mass spectra of the $S$-wave doubly heavy tetraquark states $QQbar{q}bar{q}$ ($q=u, d, s$ and $Q=c, b$) with different quantum numbers $J^P=0^+$, $1^+$, and $2^+$. The parameters in the ICMI model are extracted by fitting the conventional hadron spectra and used directly to predict the masses of tetraquark states. For heavy quarks, the uncertainties of the parameters are acquired by comparing the masses of doubly (triply) heavy baryons with these given by lattice QCD, QCD sum rule, and potential models. Several compact and stable bound states are found in both charm and bottom tetraquark sectors. The predicted mass of $ccbar ubar d$ state is compatible with the recent result of the LHCb collaboration.
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Using an extended chromomagnetic model, we perform a systematic study of the masses of the doubly heavy tetraquarks. We find that the ground states of the doubly heavy tetraquarks are dominated by color-triplet $ket{(qq)^{bar{3}_{c}}(bar{Q}bar{Q})^{3_{c}}}$ configuration, which is opposite to that of the fully heavy tetraquarks. The combined results suggest that the color-triplet configuration becomes more important when the mass difference between the quarks and antiquarks increases. We find three stable states which lie below the thresholds of two pseudoscalar mesons. They are the $IJ^{P}=01^{+}$ $nnbar{b}bar{b}$ tetraquark, the $IJ^{P}=00^{+}$ $nnbar{c}bar{b}$ tetraquark and the $J^{P}=1^{+}$ $nsbar{b}bar{b}$ tetraquark.
We outline the most important results regarding the stability of doubly heavy tetraquarks $QQbar qbar q$ with an adequate treatment of the four-body dynamics. We consider both color-mixing and spin-dependent effects. Our results are straightforwardly applied to the case of all-heavy tetraquarks $QQbar Qbar Q$. We conclude that the stability is favored in the limit $M_Q/m_q gg 1$ pointing to the stability of the $bbbar ubar d$ state and the instability of all-heavy tetraquarks.
We extend the chromomagnetic model by further considering the effect of color interaction. The effective mass parameters between quark pairs ($m_{qq}$ or $m_{qbar{q}}$) are introduced to account both the effective quark masses and the color interaction between the two quarks. Using the experimental masses of hadrons, the quark pair parameters are determined between the light quark pairs and the light-heavy quark pairs. Then the parameters of heavy quark pairs ($cc$, $cb$, $bb$) are estimated based on simple quark model assumption. We calculate all masses of doubly and triply heavy-quark baryons. The newly discovered doubly charmed baryon $Xi_{cc}$ fits into the model with an error of 12 MeV.
We study the interesting problem of interaction and identification of the hadronic molecules which seem to be deuteron-like structure. In particular, we propose a binding mechanism in which One Boson Exchange Potential plus Yukawa screen-like potential is applied in their relative s-wave state. We propose the dipole-like interaction between two color neutral states to form a hadronic molecule. For the identification of the hadronic molecules, the Weinbergs compositeness theorem is used to distinguish the molecule from confined (elementary) state. The present formalism predict some di-hadronic molecular states, involving quarks (s, c, b or $overline{s}$, $overline{c}$, $overline{b}$) as a constituents, namely, $pn$, $Koverline{K}$, $rho overline{rho}$, $K^{*}overline{K^{*}}$, $Doverline{D^{*}}$($overline{D}D^{*}$), $D^{*}overline{D^{*}}$, $Boverline{B^{*}}$, $B^{*}overline{B^{*}}$, $D^{*pm}overline{D_{1}^{0}}$, $ D^{0}overline{K^{pm}}$, $D^{*0}overline{K^{pm}}$, with their possible quantum numbers.
In this paper we present in greater detail previous work on the Born-Oppenheimer approximation to treat the hydrogen bond of QCD, and add a similar treatment of doubly heavy baryons. Doubly heavy exotic resonances X and Z can be described as color molecules of two-quark lumps, the analogue of the H_2 molecule, and doubly heavy baryons as the analog of the H_2^+ ion, except that the two heavy quarks attract each other. We compare our results with constituent quark model and lattice QCD calculations and find further evidence in support of this upgraded picture of compact tetraquarks and baryons.
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