Heavy Tetraquarks Research Articles

Rotation and Vibration in Tetraquarks

A novel approach is introduced for obtaining precise solutions of the pairing Hamiltonian for tetraquarks, which utilizes an algebraic technique in infinite dimensions. The parameters involved in the transition phase are calibrated based on potential tetraquark candidates derived from phenomenology. Our investigation shows that the rotation and vibration transitional theory delivers a reasonable agreement with other works for heavy tetraquarks compared to other methods. To illustrate the concept, we compute the spectra of several tetraquarks, namely charm, bottom, bottom–charm and open charm and bottom systems, and contrast them with those of other particles.

Prediction of charmed-bottom pentaquarks in quark model

Inspired by the fully heavy tetraquark states reported by the LHCb, ATLAS and CMS Collaborations, we perform a systematical investigation of the low-lying fully heavy pentaquark systems composed of charm and bottom quarks (anti-quark) in the chiral quark model. With the help of the channel-coupling, we obtain several fully heavy pentaquark candidates, which are ccccbar{b} and bbbbbar{c} systems with J^P = 1/2^- and 3/2^-, cccbbar{c}, bbbcbar{b}, cccbbar{b} and bbbcbar{c} systems with J^P = 5/2^-. The binding energies of these states are all below 10 MeV and the root mean square (RMS) are around 1.8 fm, which indicates that these states are likely to be molecular states. These predicted exotic states may provide new ideas for experimental searches and we expect more experimental and theoretical researches to study and understand the fully heavy states in future.

Mass spectra of doubly heavy tetraquarks in diquark−antidiquark picture* *Supported by the National Natural Science Foundation of China under the No. 12165017.

Inspired by the recent observation of the first doubly charmed tetraquark T cc , we apply the linear Regge relation and mass scaling to study low-lying mass spectra of the doubly heavy tetraquark in a heavy-diquark−light-antidiquark picture. The measured data and other compatible estimates of ground-state masses of doubly heavy baryons are employed to evaluate masses of heavy diquark M QQ (Q = c, b) and the D/D s meson masses are used in mass scaling to determine the hyperfine mass splitting. Our mass computation indicates that all low-lying states of doubly heavy tetraquarks are unstable against strong decays to two heavy-light mesons, except for the ground states of nonstrange bb tetraquarks.

Doubly heavy tetraquark multiplets as heavy antiquark-diquark symmetry partners of heavy baryons

Symmetries play important roles in the understanding of hadron structures and spectroscopy. Motivated by the discovery of the doubly charmed tetraquark ${T}_{cc}^{+}(3875)$, we study the ground states of the doubly heavy tetraquarks with the QCD inspired heavy antiquark-diquark symmetry in the constituent quark model. Six ground states of ${T}_{QQ}(Q=c,b)$ are predicted and the lightest ${T}_{cc}$ state has a mass of $3875.8\ifmmode\pm\else\textpm\fi{}7.6\text{ }\text{ }\mathrm{MeV}$ and spin-parity ${1}^{+}$, which are consistent with those of the observed ${T}_{cc}^{+}(3875)$. In addition, the magnetic moments of the predicted tetraquarks ${T}_{cc}^{+}(3876)$ and ${T}_{bb}^{\ensuremath{-}}(10396)$ are also estimated in the same model, which provide further information to distinguish the structures of the ${T}_{QQ}$ states.

Possible triply heavy tetraquark states in a chiral quark model

In the present work, the triply heavy tetraquarks states $QQ\overline{Q}\overline{q}$ with $Q=(c,b)$ and $q=(u,d,s)$ with all possible quantum numbers are systematically investigated in the framework of the chiral quark model with the resonating ground method. Two kinds of structures, including the meson-meson configuration (the color-singlet channels and the hidden-color channels) and the diquark-antidiquark configuration (the color sextet-antisextet and the color triplet-antitriplet), are considered. In the considered system, several bound states are obtained for the $cc\overline{c}\overline{{q}^{\ensuremath{'}}}$, $bb\overline{c}\overline{{q}^{\ensuremath{'}}}$, and $bc\overline{c}\overline{q}$ tetraquarks. From the present estimations, we find that the coupled-channel effect is of great significance for forming below-threshold tetraquark states, which are stable for strong decays.

Investigation of potential for heavy tetraquarks with hidden charm

Investigation of potential for heavy tetraquarks with hidden charm

Generalized fractional of the extended Nikiforov–Uvarov method for heavy tetraquark masses spectra

In this paper, the new analytic–exact energy eigenvalues and eigenfunctions are obtained in the fractional forms by using the extended Nikiforov–Uvarov approach in which the heavy diquark systems are described. We have recalculated the mass spectra and fractional radial wave of heavy tetraquarks. The mass spectra are compared to the experimental data. The present results show a good agreement with the experimental data and are improved in comparison with other studies. We conclude that the fractional models play a good role in the heavy tetraquark masses.

Analytical solution of relativistic four quark bound systems

Since in recent years most of the heavy tetraquarks are discovered by Belle, LHCb, BESIII, etc., it motivated us to study these exotic hadrons. To the extent of our knowledge about the mass characteristics of heavy tetraquarks, we utilize the spinless relativistic Bethe–Salpeter equation by applying the Cornell potential in order to calculate the eigenvalue and mass of heavy tetraquarks. For this purpose, we present an ansatz solution to obtained Schrödinger-like equation to calculate the ground-state energy of diquarks and tetraquarks. Eventually, we compare our obtained predictions for heavy tetraquark masses with available experimental and theoretical data.

Mechanisms of Fully Heavy Tetraquark Production in Proton–Proton Collisions

Mechanisms of Fully Heavy Tetraquark Production in Proton–Proton Collisions

Doubly heavy tetraquarks in the chiral quark soliton model

The chiral quark soliton model has been successfully applied to describe the heavy baryon spectrum, both for charm and bottom, leading to the conclusion that the heavy quark has no effect on the soliton. This suggests that replacing a heavy quark by a heavy antidiquark $\overline{Q}\overline{Q}$ in color triplet should give a viable description of heavy tetraquarks. We follow this strategy to compute tetraquark masses. To estimate heavy diquark masses, we use the Cornell potential with appropriately rescaled parameters. The lightest charm tetraquark is 70 MeV above the $D{D}^{*}$ threshold. On the contrary, both nonstrange and strange bottom tetraquarks are bound by approximately 140 and 60 MeV, respectively.

Masses of doubly heavy tetraquarks QQq̄n̄ with JP = 1+

In this paper, we apply the method of QCD sum rules to study the doubly heavy tetraquark states [Formula: see text] with spin-parity [Formula: see text] and strangeness [Formula: see text] using careful estimates of the Borel and threshold parameters involved. Masses of the doubly bottom and charmed tetraquarks with isospin [Formula: see text] are computed precisely via taking into account multifarious condensates up to dimension 10. Compared with the two-heavy meson thresholds, we find that all nonstrange doubly-bottom tetraquarks and a doubly-charmed tetraquarks associated with [Formula: see text] with [Formula: see text] are stable against strong decay into two bottom mesons while a doubly-charmed tetraquark associated with current [Formula: see text] is unstable against strong decay. By the way, weak decay widths of the doubly bottom tetraquarks are also given.

Fully Heavy Tetraquark Spectroscopy in the Relativistic Quark Model

Masses of the ground and excited (1P, 2S, 1D, 2P, 3S) states of the fully heavy tetraquarks, composed of charm (c) and bottom (b) quarks and antiquarks, are calculated in the diquark–antidiquark picture within the relativistic quark model based on the quasipotential approach and quantum chromodynamics. The quasipotentials of the quark–quark and diquark–antidiquark interactions are constructed similarly to the previous consideration of mesons and baryons. Relativistic effects are consistently taken into account. A tetraquark is considered a bound state of a diquark and an antidiquark. The finite size of the diquark is taken into account, using the form factors of the diquark–gluon interaction. It is shown that most of the investigated states of tetraquarks lie above the decay thresholds into a meson pair; as a result, they can be observed only as broad resonances. The narrow state X(6900) recently discovered in the di-J/ψ production spectrum by the LHCb, CMS and ATLAS Collaborations corresponds to an excited state of the fully charmed tetraquark. Other recently discovered exotic heavy resonances, X(6200), X(6400), X(6600), X(7200), and X(7300), can also be interpreted as the different excitations of the fully charmed tetraquark.

NLO results with operator mixing for fully heavy tetraquarks in QCD sum rules

We study the mass spectra of overline{Q}Qoverline{Q}Q (Q = c, b) systems in QCD sum rules with the complete next-to-leading order (NLO) contribution to the perturbative QCD part of the correlation functions. Instead of meson-meson or diquark-antidiquark currents, we use diagonalized currents under operator renormalization. We find that differing from conventional mesons overline{q}q and baryons qqq, a unique feature of the multiquark systems like overline{Q}Qoverline{Q}Q is the operator mixing or color configuration mixing induced by NLO corrections, which is crucial to understand the color structure of the states. Our numerical results show that the NLO corrections are very important for the overline{Q}Qoverline{Q}Q system, because they not only give significant contributions but also reduce the scheme and scale dependence and make Borel platform more distinct, especially for the overline{b}boverline{b}b in the overline{textrm{MS}} scheme. We use currents that have good perturbation convergence in our phenomenological analysis. With the overline{textrm{MS}} scheme, we get three JPC = 0++ states, with masses {6.35}_{-0.17}^{+0.20} GeV, {6.56}_{-0.20}^{+0.18} GeV and {6.95}_{-0.35}^{+0.21} GeV, respectively. The first two seem to agree with the broad structure around 6.2 ~ 6.8 GeV measured by the LHCb collaboration in the J/ψJ/ψ spectrum, and the third seems to agree with the narrow resonance X(6900). For the 2++ states we find one with mass {7.03}_{-0.26}^{+0.22} GeV, which is also close to that of X(6900), and another one around {7.25}_{-0.35}^{+0.21} GeV, which has good scale dependence but slightly large scheme dependence.

Study of three-flavored heavy dibaryons using lattice QCD

We present results of the first lattice QCD calculation of three-flavored heavy dibaryons both in the flavor-symmetric and antisymmetric channels. These dibaryons have spin zero, and are constructed using various possible combinations of quark flavors with at least one of them as the charm or the bottom quark, i.e., namely, $H_c(cudcud), H_b(budbud), H_{bcs}(bcsbcs)$, $H_{csl}(cslcsl), H_{bsl}(bslbsl)$ and $H_{bcl}(bclbcl)$; $l\in u,d$. We compute the ground state masses of these dibaryons and the calculations are performed on three $N_f=2+1+1$ HISQ gauge ensembles of the MILC collaboration, with lattice spacings $a =$ 0.1207, 0.0888 and 0.0582 fm. A relativistic overlap action is employed for the valence light to charm quarks while a non-relativistic-QCD Hamiltonian with improved coefficients is used for the bottom quarks. Unlike the doubly heavy tetraquarks, one and two-flavored heavy dibaryons, for which lattice QCD calculations have predicted deeply bound strong-interactions-stable states, for these $H_c, H_b, H_{csl},H_{bsl}$ dibaryons we do not find any such deeply bound state. However, for $H_{bcs}$, our results indicate the presence of an energy level $29\pm 24$ MeV below the lowest two-baryon threshold, which could be relevant for its future experimental searches. Moreover, we find that the energy difference between the ground state of $H_{bcl}$ and its lowest threshold increases when $m_l>m_s$. Taken together, our findings indicate the possibility of the existence of the $H_{bcs}$ dibaryon while all other physical three-flavored dibaryons are much closer to their thresholds suggesting either they are weakly bound or unbound, resolving which requires further detail study. Our results also point that the binding of a dibaryon configuration becomes stronger with the increase of its valence quark masses which suggests an interesting aspect of strong interactions at multiple scales.

Fully heavy hexaquark states via the QCD sum rules

In this paper, we construct the diquark–diquark–diquark-type vector six-quark currents to investigate the vector and scalar hexaquark states in the framework of the QCD sum rules in a consistent way, and make predictions for the hexaquark masses. We can search for the fully heavy hexaquark states in the di-[Formula: see text] and di-[Formula: see text] invariant mass spectra in the future. Combined with our previous works on the fully heavy tetraquark states and pentaquark states, the present predictions can shed light on the nature of the fully heavy multiquark states.

Decoding the double heavy tetraquark state [formula omitted

We analyse the deuteron-like $T^+_{cc}$ state observed by the LHCb Collaboration from the perspective of the quark clustering. The $T^+_{cc}$ state implies the possible existence of other compact doubly heavy tetraquark states.

Production mechanism of fully heavy tetraquarks in proton-proton collisions

We discuss the production mechanism of fully charm tetraquark, observed last year by the LHCb at M = 6.9 GeV in the J/ψJ/ψ channel. Both single parton scattering (SPS) and double parton scattering (DPS) mechanisms are considered. We calculate the distribution in the invariant mass of the four-quark system, M4c, for SPS and DPS production of ccc¯c¯ in the kt-factorization approach. We present transverse momentum distribution in pt,4c for ccc¯ c¯ system in a mass window around tetraquark mass. The calculation of the SPS g ∗ g ∗ → T4c(6900) fusion mechanism is performed in the kT -factorization approach assuming different spin scenarios (0 + and 0 −).

Doubly heavy tetraquarks in a chiral-diquark picture

Energy spectrum of doubly heavy tetraquarks, $T_{QQ}$ ($QQ \bar{q} \bar{q}$ with $Q = c, b$ and $q = u, d, s$), is studied in the potential chiral-diquark model. Using the chiral effective theory of diquarks and the quark-diquark-based potential model, the $T_{bb}$, $T_{cc}$, and $T_{cb}$ tetraquarks are described as a three-body system composed of two heavy quarks and an antidiquark. We find several $T_{bb}$ bound states, while no $T_{cc}$ and $T_{cb}$ (deep) bound state is seen. We also study the change of the $T_{QQ}$ tetraquark masses under restoration of chiral symmetry.

An analytical approach to the mass spectrum of heavy tetraquarks in dimeson model

An analytical approach to the mass spectrum of heavy tetraquarks in dimeson model

Lineshape of the compact fully heavy tetraquark

Hadrons and their distributions are the most direct observables in experiment, which would shed light on the non-perturbative mystery of quantum chromodynamics (QCD). As the result, any new hadron will challenge our current knowlege on the one hand, and provide additional inputs on the other hand. The fully heavy $cc\bar{c}\bar{c}$ system observed by LHCb recently opens a new era for hadron physics. We first extract the internal structure of the fully heavy tetraquarks directly from the experimental data, within the compact tetraquark picture. By fitting to the di-$J/\psi$ lineshape, we find that the $X(6900)$ is only cusp effect from the $J/\psi\psi(3770)$ channel. In addition, there is also a cusp slightly below $6.8~\mathrm{GeV}$ stemming from the $J/\psi\psi^\prime$ channel. The two $0^{++}$ tetraquarks behave as two resonances above the di-$\eta_c$ and di-$J/\psi$ threshold, respectively. The $2^{++}$ state is a bound state below the di-$J/\psi$ threshold. Furthermore, we find that the $X_{0^{++}}(6035)$ shows a significant structure in the di-$\eta_c$ lineshape even after the coupled channel effect. This is an unique feature which can distinguish compact $cc\bar{c}\bar{c}$ tetraquark from the loosely hadronic molecules.