Diquark-antidiquark Type Research Articles

Analysis of the hidden-charm-hidden-strange tetraquark mass spectrum via the QCD sum rules

In the present work, we construct the diquark-antidiquark type four-quark currents to investigate the mass spectrum of the ground state hidden-charm-hidden-strange tetraquark states with the quantum numbers JPC=0++, 1+−, 1++ and 2++ via the traditional QCD sum rules in a comprehensive way. We update old calculations, perform new calculations and analysis in a rigorous way, and take account of the net light-flavor SU(3) breaking effects in a consistent way. And we make more reasonable identifications for the X(3960), X(4140), X(4274), X(4500), X(4685) and X(4700) and supersede some old identifications. Furthermore, we consider our previous theoretical predictions, and make reasonable/suitable identifications of the new LHCb states hc(4000) and χc1(4010).

Ground states and first radial excitations of vector tetraquark states with explicit P-waves via QCD sum rules* *Supported by the National Natural Science Foundation of China (12175068)

In this study, we chose the diquark-antidiquark type four-quark currents with an explicit P-wave between the diquark and antidiquark pairs to study the ground states and first radial excitations of the hidden-charm tetraquark states with quantum numbers . We also obtained the lowest vector tetraquark masses and made possible assignments of the existing states. There indeed exists a hidden-charm tetraquark state with at an energy of approximately 4.75 GeV as the first radial excitation that accounts for the BESIII data.

Fully-light vector tetraquark states with explicit P-wave via QCD sum rules*

Abstract In this study, we apply the QCD sum rules to investigate the vector fully-light tetraquark states with an explicit P-wave between the diquark and antidiquark pairs. We observed that the (or ) type current with fully-strange quarks couples potentially to a tetraquark state with a mass , which supports assigning as the diquark-antidiquark type tetraquark state with . The and vector tetraquark states with the structure (or ) are consistent with and , respectively, which lie in the region from to . The central values of the masses of the fully-strange vector tetraquark states with an explicit P-wave are approximately (or ). Predictions for other fully-light vector tetraquark states with and without hidden-strange are also presented.

D-wave excited tetraquark states with and * *Supported by the National Natural Science Foundation of China (12175318), the National Key R & D Program of China (2020YFA0406400), the Natural Science Foundation of Guangdong Province of China (2022A1515011922), and the Fundamental Research Funds for the Central Universities

We study the mass spectra of D-wave excited tetraquark states with and in both symmetric and antisymmetric color configurations using the QCD sum rule method. We construct the D-wave diquark-antidiquark type of tetraquark interpolating currents in various excitation structures with . Our results support the interpretation of the recently observed resonance as a D-wave tetraquark state with in the or excitation mode, although some other possible excitation structures cannot be excluded exhaustively within theoretical errors. Moreover, our results provide the mass relations and for the positive and negative -parity D-wave tetraquarks, respectively. We suggest searching for these possible D-wave tetraquarks in both the hidden-charm channels and , as well as open-charm channels such as and .

Analysis of the X(6600), X(6900), X(7300) and related tetraquark states with the QCD sum rules

In this work, we re-investigate the mass spectrum of the ground state, first, second and third radial excited states of the diquark-antidiquark type fully-charm tetraquark states with the QCD sum rules plus Regge trajectories. We take account of the CMS and ATLAS experimental data and preform a self-consistent analysis, then try to make possible assignments of the X(6600), X(6900) and X(7300) in the picture of tetraquark states with the JPC=0++ or 1+−.

Analysis of Zcs (3985) as the axialvector tetraquark state * *Supported by National Natural Science Foundation of China (11775079)

In this study, we choose the scalar and axialvector diquark operators in the color antitriplet as the fundamental building blocks to construct four-quark currents and investigate the diquark-antidiquark type axialvector tetraquark states in the framework of the QCD sum rules. The predicted tetraquark mass is in excellent agreement with the experimental value from the BESIII collaboration, which supports identifying as the cousin of with quantum numbers . We take into account the light flavor mass-breaking effect to estimate the mass spectrum of the diquark-antidiquark type hidden-charm tetraquark states with strangeness according to previous studies.

Vector hidden-bottom tetraquark candidate: Y(10750) * * Supported by National Natural Science Foundation (11775079)

In this article, we take the scalar diquark and antidiquark operators as the basic constituents, and construct the type tetraquark current to study Y(10750) with the QCD sum rules. The predicted mass and width support the assignment of Y(10750) as the diquark-antidiquark type vector hidden-bottom tetraquark state, with a relative P-wave between the diquark and antidiquark constituents.

Analysis of the axial vector Bc-like tetraquark states with the QCD sum rules

In this paper, we construct the diquark-antidiquark–type current operators to study the axial vector Bc-like tetraquark states with the QCD sum rules. In the calculations, we take the energy scale formula as a powerful constraint to choose the ideal energy scales of the QCD spectral densities and add detailed discussions to illustrate why we take the energy scale formula to improve the QCD sum rules for the doubly heavy tetraquark states. The predicted masses and lie between the conventional 2P and 3P Bc states with from the potential quark models, which is a typical feature of the diquark-antidiquark–type Bc-like tetraquark states.

The magnetic moment of the Z_c(3900) as an axialvector tetraquark state with QCD sum rules

In this article, we assign the Z_c^pm (3900) to be the diquark-antidiquark type axialvector tetraquark state, study its magnetic moment with the QCD sum rules in the external weak electromagnetic field by carrying out the operator product expansion up to the vacuum condensates of dimension 8. We pay special attention to matching the hadron side with the QCD side of the correlation function to obtain solid duality, the routine can be applied to study other electromagnetic properties of the exotic particles.

The decay width of the Z_c(3900) as an axialvector tetraquark state in solid quark\u2013hadron duality

In this article, we tentatively assign the Z_c^pm (3900) to be the diquark–antidiquark type axialvector tetraquark state, study the hadronic coupling constants G_{Z_cJ/psi pi }, G_{Z_ceta _crho }, G_{Z_cD bar{D}^{*}} with the QCD sum rules in details. We take into account both the connected and disconnected Feynman diagrams in carrying out the operator product expansion, as the connected Feynman diagrams alone cannot do the work. Special attentions are paid to matching the hadron side of the correlation functions with the QCD side of the correlation functions to obtain solid duality, the routine can be applied to study other hadronic couplings directly. We study the two-body strong decays Z_c^+(3900)rightarrow J/psi pi ^+, eta _crho ^+, D^+ bar{D}^{*0}, bar{D}^0 D^{*+} and obtain the total width of the Z_c^pm (3900). The numerical results support assigning the Z_c^pm (3900) to be the diquark–antidiquark type axialvector tetraquark state, and assigning the Z_c^pm (3885) to be the meson–meson type axialvector molecular state.

Investigating efficient methods for computing four-quark correlation functions

We discuss and compare the efficiency of various methods, combinations of point-to-all propagators, stochastic timeslice-to-all propagators, the one-end trick and sequential propagators, to compute two-point correlation functions of two-quark and four-quark interpolating operators of different structure including quark–antiquark type, mesonic molecule type, diquark–antidiquark type and two-meson type. Although we illustrate our methods in the context of the a0(980), they can be applied for other multi-quark systems, where similar diagrams appear. Thus our results could provide helpful guidelines on the choice of methods for correlation function computation for future lattice QCD studies of meson–meson scattering and possibly existing tetraquark states.

Analysis of the QQbar{Q}bar{Q} tetraquark states with QCD sum rules

In this article, we study the J^{PC}=0^{++} and 2^{++}QQbar{Q}bar{Q} tetraquark states with the QCD sum rules, and we obtain the predictions M_{X(ccbar{c}bar{c},0^{++})} =5.99pm 0.08,mathrm {GeV}, M_{X(ccbar{c}bar{c},2^{++})} =6.09pm 0.08,mathrm {GeV}, M_{X(bbbar{b}bar{b},0^{++})} =18.84pm 0.09,mathrm {GeV} and M_{X(bbbar{b}bar{b},2^{++})} =18.85pm 0.09,mathrm {GeV}, which can be confronted to the experimental data in the future. Furthermore, we illustrate that the diquark–antidiquark type tetraquark state can be taken as a special superposition of a series of meson–meson pairs and that it embodies the net effects.

Reanalysis of X(4140) as axial-vector tetraquark state with QCD sum rules

In this article, we take X(4140) as the diquark–antidiquark type $$cs\bar{c}\bar{s}$$ tetraquark state with $$J^{PC}=1^{++}$$ , and we study the mass and pole residue with the QCD sum rules in detail by constructing two types of interpolating currents. The numerical results $$M_{X_{L,+}}=3.95\pm 0.09\,\mathrm{GeV}$$ and $$M_{X_{H,+}}=5.00\pm 0.10\,\mathrm{GeV}$$ disfavor assigning the X(4140) to the $$J^{PC}=1^{++}$$ diquark–antidiquark type $$cs\bar{c}\bar{s}$$ tetraquark state. Moreover, we obtain the masses of the $$J^{PC}=1^{+-}$$ diquark–antidiquark type $$cs\bar{c}\bar{s}$$ tetraquark states as a byproduct. The present predictions can be confronted to the experimental data in the future.

Analysis of X(5568) as Scalar Tetraquark State in Diquark-Antidiquark Model with QCD Sum Rules**Supported by National Natural Science Foundation under Grant No. 11375063, and Natural Science Foundation of Hebei Province under Grant No. A2014502017

In this article, we take the X(5568) as the diquark-antidiquark type tetraquark state with the spin-parity JP = 0+, construct the scalar-diquark-scalar-antidiquark type current, carry out the operator product expansion up to the vacuum condensates of dimension-10, and study the mass and pole residue in details with the QCD sum rules. We obtain the value MX = (5.57±0.12) GeV, which is consistent with the experimental data. The present prediction favors assigning the X(5568) to be the scalar tetraquark state.

Tetraquark state candidates: Y(4260), Y(4360), Y(4660), and $$Z_c(4020/4025)$$ Z c ( 4020 / 4025 )

In this article, we construct the axialvector-diquark-axialvector-antidiquark type tensor current to interpolate both the vector and axialvector tetraquark states, then calculate the contributions of the vacuum condensates up to dimension-10 in the operator product expansion, and obtain the QCD sum rules for both the vector and axialvector tetraquark states. The numerical results support assigning the $Z_c(4020/4025)$ to be the $J^{PC}=1^{+-}$ diquark-antidiquark type tetraquark state, and assigning the $Y(4660)$ to be the $J^{PC}=1^{--}$ diquark-antidiquark type tetraquark state. Furthermore, we take the $Y(4260)$ and $Y(4360)$ as the mixed charmonium-tetraquark states, and construct the two-quark-tetraquark type tensor currents to study the masses and pole residues. The numerical results support assigning the $Y(4260)$ and $Y(4360)$ to be the mixed charmonium-tetraquark states.

Analysis of the Zc(4200) as axial-vector molecule-like state

In this paper, we assume the [Formula: see text] as the color octet–octet type axial-vector molecule-like state, and construct the color octet–octet type axial-vector current to study its mass and width with the QCD sum rules. The numerical values [Formula: see text] and [Formula: see text] are consistent with the experimental data [Formula: see text] and [Formula: see text], and support assigning the [Formula: see text] to be the color octet–octet type molecule-like state with [Formula: see text]. Furthermore, we discuss the possible assignments of the [Formula: see text], [Formula: see text] and [Formula: see text] as the diquark–antidiquark type tetraquark states with [Formula: see text].

Reanalysis of the Z c (4020), Z c (4025), Z(4050) and Z(4250) as Tetraquark States with QCD Sum Rules* *Supported by National Natural Science Foundation of Chian under Grant No. 11375063, and Natural Science Foundation of Hebei Province under Grant No. A2014502017

In this article, we calculate the contributions of the vacuum condensates up to dimension-10 in the operator product expansion, and study the Cγμ — Cγν type scalar, axial-vector and tensor tetraquark states in details with the QCD sum rules. In calculations, we use the formula to determine the energy scales of the QCD spectral densities. The predictions favor assigning the Zc(4020) and Zc(4025) as the JPC = 1+− or 2++ diquark-antidiquark type tetraquark states, while the prediction disfavors assigning the Z(4050) and Z(4250) as the JPC = 0++ diquark-antidiquark type tetraquark states. Furthermore, we discuss the strong decays of the 0++, 1+−, 2++ diquark-antidiquark type tetraquark states in details.

Tetraquark state candidates: Y(4140), Y(4274) and X(4350)

In this paper, we tentatively assign the Y(4140), Y(4274) and X(4350) to be the scalar and tensor [Formula: see text] tetraquark states, respectively, and study them with the QCD sum rules. In the operator product expansion, we take into account the vacuum condensates up to dimension-10. In calculations, we use the formula [Formula: see text] to determine the energy scales of the QCD spectral densities. The numerical results favor assigning the Y(4140) to be the JPC = 2++ diquark–antidiquark type tetraquark state, and disfavor assigning the Y(4274) and X(4350) to be the 0++ or 2++ tetraquark states.

Analysis of the $$Z_c(4020)$$ Z c ( 4020 ) , $$Z_c(4025)$$ Z c ( 4025 ) , $$Y(4360)$$ Y ( 4360 ) , and $$Y(4660)$$ Y ( 4660 ) as vector tetraquark states with QCD sum rules

In this article, we distinguish the charge conjugations of the interpolating currents, calculate the contributions of the vacuum condensates up to dimension-10 in the operator product expansion, and study the masses and pole residues of the $J^{PC}=1^{-\pm}$ hidden charmed tetraquark states with the QCD sum rules. We suggest a formula $\mu=\sqrt{M^2_{X/Y/Z}-(2{\mathbb{M}}_c)^2}$ with the effective mass ${\mathbb{M}}_c=1.8\,\rm{GeV}$ to estimate the energy scales of the QCD spectral densities of the hidden charmed tetraquark states, which works very well. The numerical results disfavor assigning the $Z_c(4020)$, $Z_c(4025)$, $Y(4360)$ as the diquark-antidiquark (with the Dirac spinor structure $C-C\gamma_\mu$) type vector tetraquark states, and favor assigning the $Z_c(4020)$, $Z_c(4025)$ as the diquark-antidiquark type $1^{+-}$ tetraquark states. While the masses of the tetraquark states with symbolic quark structures $c\bar{c}s\bar{s}$ and $c\bar{c}(u\bar{u}+d\bar{d})/\sqrt{2}$ favor assigning the $Y(4660)$ as the $1^{--}$ diquark-antidiquark type tetraquark state, more experimental data are still needed to distinguish its quark constituents. There are no candidates for the positive charge conjugation vector tetraquark states, the predictions can be confronted with the experimental data in the future at the BESIII, LHCb and Belle-II.

Chiral nonet mixing inππscattering

Pion-pion scattering is studied in a generalized linear sigma model which contains two scalar nonets (one of quark-antiquark type and the other of diquark-antidiquark type) and two corresponding pseudoscalar nonets. An interesting feature concerns the mixing of the four isosinglet scalar mesons which yield poles in the scattering amplitude. Some realism is introduced by enforcing exact unitarity via the K-matrix method. It is shown that a reasonable agreement with experimental data is obtained up to about 1 GeV. The poles in the unitarized scattering amplitude are studied in some detail. The lowest pole clearly represents the sigma meson (or ${f}_{0}(600)$) with a mass and decay width around 500 MeV. The second pole invites comparison with the ${f}_{0}(980)$ which has a mass around 1 GeV and decay width around 100 MeV. The third and fourth poles, resemble some of the isosinglet state in the complicated 1--2 GeV region. Some comparison is made to the situation in the usual SU(3) linear sigma model with a single scalar nonet.