Scalar or Vector Tetraquark State Candidate: Z_c(4100)

In this article, we separate the vector and axialvector components of the tensor diquark operators explicitly,construct the axialvector-axialvector type and vector-vector type scalar tetraquark currents and scalar-tensor type tensor tetraquark current to study the scalar, vector and axialvector tetraquark states with the QCD sum rules in a consistent way. The present calculations do not favor assigning the Zc(4100) to be a scalar or vector tetraquark state. If the Zc(4100) is a scalar tetraquark state without mixing effects, it should have a mass about 3.9 GeV or 4.0 GeV rather than4.1 GeV; on the other hand, if the Zc(4100) is a vector tetraquark state, it should have a mass about 4.2 GeV rather than 4.1 GeV. However, if we introduce mixing, a mixing scalar tetraquark state can have a mass about 4.1 GeV. As a byproduct, we obtain an axialvector tetraquark candidate for the Zc(4020).     

Analysis of the Z(4430) as the First Radial Excitation of the Z_c(3900)

In this article,we take the Zc(3900) and Z(4430) as the ground state and the first radial excited state of the axial-vector tetraquark states with J~(PC) = 1~(+-),respectively,and study their masses and pole residues with the QCD sum rules by calculating the contributions of the vacuum condensates up to dimension-10 in a consistent way in the operator product expansion.The numerical result favors assigning the Z_c(3900) and Z(4430) as the ground state and first radial excited state of the axial-vector tetraquark states,respectively.     

Reanalysis of the Z_c(4020), Z_c(4025), Z(4050) and Z(4250) as Tetraquark States with QCD Sum Rules

In this article, we calculate the contributions of the vacuum condensates up to dimension-10 in the operator product expansion, and study the C γμ- Cγνtype scalar, axial-vector and tensor tetraquark states in details with the QCD sum rules. In calculations, we use the formula μ = (M 2X/ Y /Z-(2Mc)2)~(1/2) to determine the energy scales of the QCD spectral densities. The predictions MJ =2=(4.02+0.09-0.09) GeV, MJ =1=(4.02+0.07-0.08) GeV favor assigning the Zc(4020) and Zc(4025) as the JP C= 1+-or 2++diquark-antidiquark type tetraquark states, while the prediction M++J =0=(3.85+0.15-0.09) GeV disfavors assigning the Z(4050) and Z(4250) as the JP C= 0diquark-antidiquark type tetraquark states. Furthermore, we discuss the strong decays of the 0++, 1+-, 2++diquark-antidiquark type tetraquark states in details.     

可能的qQqQ,qqQQ和qQQQ重四夸克态

假设X(3872)是一个qcqc四夸克态, 并用它的质量作为输入, 用具有味对称性破坏的色磁相互作用系统研究了可能的重四夸克态的质量谱.     

D(s0)+ (2317)-D0(2308) mass difference as evidence for tetraquarks

We argue that the anomalously small mass difference between the D(s0)+ (2317) and the recently observed D0(2308) (Belle) state is the first "smoking gun" experimental evidence of their tetraquark [cq(q q)] structure. The recently reported D(sJ)+ (2632) (SELEX) state completes the low-lying nonexotic tetraquark spectrum, as predicted by 't Hooft's instanton-induced effective quark interaction.     

AdS-QCD quark–antiquark potential,meson spectrum and tetraquarks

The AdS/QCD correspondence predicts the structure of the quark–antiquark potential in the static limit. We use this piece of information together with the Salpeter equation (Schrödinger equation with relativistic kinematics) and a short range hyperfine splitting potential to determine quark masses and the quark potential parameters from the meson spectrum. The agreement between theory and experimental data is satisfactory, provided one considers only mesons comprising at least one heavy quark. We use the same potential (in the one-gluon-exchange approximation) and these data to estimate the constituent diquark masses. Using these results as input we compute tetraquark masses using a diquark–antidiquark model. The masses of the states X(3872) or Y(3940) are predicted rather accurately. We also compute tetraquark masses with open charm and strangeness. Our result is that tetraquark candidates such as D _s (2317), D _s (2457) or X(2632) can hardly be interpreted as diquark–antidiquark states within the present approach.     

Production of Tetraquark State T_(cc) at B-Factories

We study production of the tetraquark state Tcc via virtual photon at the B-factories in the QCD factor- ization framework. We predict the cross section of tetraquark state production in the leading order at the B-factories.     

Is Ds(2700) a charmed tetraquark state?

In this article,we assume that the Ds(2700) is a tetraquark state,which consists of a scalar diquark and a vector antidiquark,and calculate its mass with the QCD sum rules.The numerical result indicates that the mass of the vector charmed tetraquark state is about Mv = (3.75±0.18) GeV or Mv = (3.71±0.15) GeV from different sum rules,which is about 1 GeV larger than the experimental data.Such tetraquark component should be very small in the Ds(2700).     

Three-body force and the tetraquark interpretation of light scalar mesons

We study the possible tetraquark interpretation of light scalar meson states a0(980), f0(980), κ,σ within the framework of the non-relativistic potential model. The wave functions of tetraquark states are obtained in a space spanned by multiple Gaussian functions. We find that the mass spectra of the light scalar mesons can be well accommodated in the tetraquark picture if we introduce a three-body quark interaction in the quark model. Using the obtained multiple Gaussian wave functions, the decay constants of tetraquarks are also calculated within the "fall apart" mechanism.     

Analysis of X（1576） as a Tetraquark State with the QCD Sum Rules

We take the viewpoint that X（1576） is the tetraquark state which consists of a scalar diquark and an antiscalar-diquark in relative P-wave, and calculate its mass in the framework of the QCD sum rule approach. The numerical value of the mass mx= （1.66 =k 0.14） GeV is consistent with the experimental data. There might be some tetraquark components in the vector meson X（1576）.     

Analysis of X(5568) as Scalar Tetraquark State in Diquark-Antidiquark Model with QCD Sum Rules

In this article, we take the X(5568) as the diquark-antidiquark type tetraquark state with the spin-parity J^P=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 M_X=(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.     

X_0(2900) and X_1(2900):Hadronic Molecules or Compact Tetraquarks

Very recently the LHCb collaboration reported their observation of the first two fully open-flavor tetraquark states,the X₀(2900) of J^P=0⁺ and the X₁(2900) of J^P=1^-.We study their possible interpretations using the method of QCD sum rules,paying special attention to an interesting feature of this experiment that the higher resonance X₁(2900) has a width significantly larger than the lower one X₀(2900).Our res...     

0~+ tetraquark states from improved QCD sum rules:delving into X(5568)

In order to investigate the possibility of the recently observed X(5568) being a 0~+ tetraquark state, we make an improvement to the study of the related various configuration states in the framework of the QCD sum rules. Particularly, to ensure the quality of the analysis, condensates up to dimension 12 are included to inspect the convergence of operator product expansion(OPE) and improve the final results of the studied states. We note that some condensate contributions could play an important role on the OPE side. By releasing the rigid OPE convergence criterion, we arrive at the numerical value 5.57+0.35 for the scalar-scalar diquark-antidiquark 0~+ -0.23 Ge Vstate, which agrees with the experimental data for the X(5568) and could support its interpretation in terms of a 0~+ tetraquark state with the scalar-scalar configuration. The corresponding result for the axial-axial current is calculated to be 5.77+0.44 still consistent with the mass of X(5568) in view of the uncertainty. The feasibility of-0.33 Ge V, which isX(5568) being a tetraquark state with the axial-axial configuration therefore cannot be definitely excluded. For the pseudoscalar-pseudoscalar and the vector-vector cases, their unsatisfactory OPE convergence make it difficult to find reasonable work windows to extract the hadronic information.     

Can X(3872) be a JP=2- Tetraquark State?

In this article, we test the nature of X(3872), which is assumed to be a P-wave [cq]-scalar-diquark [cq]-axial-vector-antidiquark tetraquark state with J^P=2^-. The interpolating current representing the J^P=2^- state is proposed. Technically, contributions of the operators up to dimension six are included in the operator product expansion. The mass obtained for such state is m_2-=(4.38? 0.15) GeV. We conclude that it is impossible to describe the X(3872) structure as J^P=2^- tetraquark state.     

Light scalar tetraquarks from a holographic perspective

We discuss how a dominant tetraquark component of the lightest scalar mesons may emerge in AdS/QCD gravity duals. In particular, we show that the exceptionally strong binding required to render the tetraquark ground state lighter than the lowest-lying scalar quark–antiquark nonet can be holographically encoded into bulk-mass corrections for the tetraquark's dual mode. The latter are argued to originate from the anomalous dimension of the corresponding four-quark interpolator. To provide a concrete example, we implement this mechanism into the dilaton soft-wall dual for holographic QCD. Preventing the lowest-lying dual mode from collapsing into the AdS boundary then establishes a rather generic lower bound on the tetraquark mass (which may be overcome in the presence of additional background fields). We further demonstrate that the higher tetraquark excitations can become heavier than their quark–antiquark counterparts and are thus likely to dissolve into the multiparticle continuum.     

The ■ tetraquark states and the structure of X(2239) observed by the BESⅢ collaboration

We investigate the mass spectrum of the■tetraquark states in the relativized quark model.By solving the Schrodinger-like equation with the relativized potential,the masses of S-and P-wave■tetraquarks are obtained.The screening effects are also taken into account.It is found that the resonant structureX(2239)observed in thee+e-→K+K-process by the BESIII collaboration can be assigned as a P-wave 1--■tetraquark state.Furthermore,the radiative transition and the strong decay behavior of this structure are also estimated,which can provide helpful information for future experimental searches.     

Decay properties of the X(3872) through the Fierz rearrangement

We systematically construct all the tetraquark currents of J^PC = 1⁺⁺ with the quark configurations $[{cq}][\bar{c}\bar{q}]$, $[\bar{c}q][\bar{q}c]$, and $[\bar{c}c][\bar{q}q]$ (q = u/d). Their relations are derived using the Fierz rearrangement of the Dirac and color indices, through which we study decay properties of the X(3872) under both the compact tetraquark and hadronic molecule interpretations. We conduct a search for the X(3872) → χ_c0π, η_cππ, and χ_c1ππ decay processes in particle experiments.     

Tetraquark-based analysis and predictions of the cross sections and distributions for the processes e+e-→Υ(1S)(π+π-,K+K-,ηπ0) near Υ(5S)

We calculate the cross sections and final state distributions for the processes e(+)e(-)→Υ(1S)×(π(+)π(-),K(+)K(-),ηπ(0)) near the Υ(5S) resonance based on the tetraquark hypothesis. This framework is used to analyze the data on the Υ(1S)π(+)π(-) and Υ(1S)K(+)K(-) final states [K.?F. Chen et al. (Belle Collaboration), Phys. Rev. Lett. 100, 112001 (2008); I. Adachi et al. (Belle Collaboration), Phys. Rev. D 82, 091106 (2010).], yielding good fits. Dimeson invariant-mass spectra in these processes are shown to be dominated by the corresponding light scalar and tensor states. The resulting correlations among the cross sections are worked out. We also predict σ(e(+)e(-)→Υ(1S)K(+)K(-))/σ(e(+)e(-)→Υ(1S)K(0)K(0))=1/4. These features provide crucial tests of the tetraquark framework and can be searched for in the currently available and forthcoming data from the B factories.     

Possible assignments of the X(3872), Z_c(3900), and Z_b(10610) as axial-vector molecular states

Higgs Computed Axial Tomography, an excerpt. The Higgs boson lineshape ( $\dots $ and the devil hath power to assume a pleasing shape, Hamlet, Act II, scene 2) is analyzed for the ${\mathrm{g}}{\mathrm{g}}\rightarrow {\mathrm{Z}}{\mathrm{Z}}$ process, with special emphasis on the off-shell tail which shows up for large values of the Higgs virtuality. The effect of including background and interference is also discussed. The main focus of this work is on residual theoretical uncertainties, discussing how much-improved constraint on the Higgs intrinsic width can be revealed by an improved approach to analysis.