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Register a new userScalar Fully-heavy Tetraquark States $QQ^prime bar{Q} bar{Q^prime}$ in QCD Sum Rules
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Very recently, the LHCb Collaboration observed distinct structures with the $ccbar{c}bar{c}$ in the $J/Psi$-pair mass spectrum. In this work, we construct four scalar ($J^{PC} = 0^{++}$) $[8_c]_{Qbar{Q^prime}}otimes [8_c]_{Q^prime bar{Q}}$ type currents to investigate the fully-heavy tetraquark state $Q Q^prime bar{Q} bar{Q^prime}$ in the framework of QCD sum rules, where $Q=c, b$ and $Q^prime = c, b$. Our results suggest that the broad structure around 6.2-6.8 GeV can be interpreted as the $0^{++}$ octet-octet tetraquark states with masses $6.44pm 0.11$ GeV and $6.52pm 0.10$ GeV, and the narrow structure around $6.9$ GeV can be interpreted as the $0^{++}$ octet-octet tetraquark states with masses $6.87pm 0.11$ GeV and $6.96pm 0.11$ GeV, respectivley. Extending to the b-quark sector,the masses of their fully-bottom partners are found to be around 18.38-18.59 GeV. Additionally, we also analyze the spectra of the $[cbar{c}][bbar{b}]$ and $[cbar{b}] [b bar{c}]$ tetraquark states, which lie in the range of 12.51-12.74 GeV and 12.49-12.81 GeV, respectively.
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We analyze the weak decay of doubly-heavy baryon decays into anti-triplets $Lambda_Q$ with light-cone sum rules. To calculate the decay form factors, both bottom and charmed anti-triplets $Lambda_b$ and $Lambda_c$ are described by the same set of leading twist light-cone distribution functions. With the obtained form factors, we perform a phenomenology study on the corresponding semi-leptonic decays. The decay widths are calculated and the branching ratios given in this work are expected to be tested by future experimental data, which will help us to understand the underlying dynamics in doubly-heavy baryon decays.
As a continuation of our previous work, we investigate the weak decays of doubly-heavy baryons $Xi_{QQ^{prime}}$ into sextet $Sigma_{Q^{prime}}$ with light-cone sum rules. We calculate the form factors for these decays with the parallel light-cone distribution amplitudes of $Sigma_{Q^{prime}}$. Numerical results of these form factors are used to predict the decay widths and branching ratios of the corresponding semi-leptonic processes. Parametric uncertainties and theoretical analyses are also given in detail. We find that the decay widths of $Xi_{cc}$ and $Xi_{bc}$ decays are several orders of magnitude larger than those of $Xi_{bb}$ decays.
In the framework of the color-magnetic interaction, we systematically investigate the mass spectrum of the tetraquark states composed of four heavy quarks with the $QQbar Qbar Q$ configuration in this work. We also show their strong decay patterns. Stable or narrow states in the $bbbar{b}bar{c}$ and $bcbar{b}bar{c}$ systems are found to be possible. We hope the studies shall be helpful to the experimental search for heavy-full exotic tetraquark states.
We use QCD sum rules to study the possible existence of $QQ-bar{u}bar{d}$ mesons, assumed to be a state with $J^{P}=1^{+}$. For definiteness, we work with a current with an axial heavy diquark and a scalar light antidiquark, at leading order in $alpha_s$. We consider the contributions of condensates up to dimension eight. For the $b$-quark, we predict $M_{T_{bb}}= (10.2pm 0.3) {rm GeV}$, which is below the $bar{B}bar{B}^*$ threshold. For the $c$-quark, we predict $M_{T_{cc}}= (4.0pm 0.2) {rm GeV}$, in agreement with quark model predictions.
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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