Diquark and light four-quark states

Zhang, Ailin; Huang, Tao; Steele, T. G.

doi:10.1103/physrevd.76.036004

Cited by 46 publications

(40 citation statements)

References 82 publications

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“…However, there is no direct correspondence between the constituent quark picture and the operator (current) quark picture. Diquarks are thus not a meaningful concept in sum rule approaches [1134], and care must be taken not to overinterpret the results. Brito et al found that the mesons decay constants and hadronic couplings are consistent with a tetraquark structure for the light scalar mesons [1135].…”

Section: A Low-mass Nonet Of Scalar Mesonsmentioning

confidence: 99%

Glueballs, hybrids, multiquarks

2007

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Glueballs, hybrids and multiquark states are predicted as bound states in models guided by quantum chromo dynamics (QCD), by QCD sum rules or QCD on a lattice. Estimates for the (scalar) glueball ground state are in the mass range from 1000 to 1800 MeV, followed by a tensor and a pseudoscalar glueball at higher mass. Experiments have reported evidence for an abundance of meson resonances with 0 −+ , 0 ++ and 2 ++ quantum numbers. In particular, the sector of scalar mesons is full of surprises starting from the elusive and mesons. The a 0 (980) and f 0 (980), discussed extensively in the literature, are reviewed with emphasis on their Janus-like appearance as KK molecules, tetraquark states or qq mesons. Most exciting is the possibility that the three mesons f 0 (1370), f 0 (1500), and f 0 (1710) might reflect the appearance of a scalar glueball in the world of quarkonia. However, the existence of f 0 (1370) is not beyond doubt and there is evidence that both f 0 (1500) and f 0 (1710) are flavour octet states, possibly in a tetraquark composition. We suggest a scheme in which the scalar glueball is dissolved into the wide background into which all scalar flavour-singlet mesons collapse.There is an abundance of meson resonances with the quantum numbers of the . Three states are reported below 1.5 GeV/c 2 whereas quark models expect only one, perhaps two. One of these states, (1440), was the prime glueball candidate for a long time. We show that (1440) is the first radial excitation of the meson.Hybrids may have exotic quantum numbers which are not accessible by qq mesons. There are several claims for J P C = 1 −+ exotics, some of them with properties as predicted from the flux tube model interpreting the quark-antiquark binding by a gluon string. The evidence for these states depends partly on the assumption that meson-meson interactions are dominated by s-channel resonances. Hybrids with non-exotic quantum numbers should appear as additional states. Light-quark mesons exhibit a spectrum of (squared) masses which are proportional to the sum of orbital angular momentum and radial quantum numbers. Two states do not fall under this classification. They are discussed as hybrid candidates.The concept of multiquark states has received revived interest due to new resonances in the spectrum of states with open and hidden charm. The new states are surprisingly narrow and their masses and their decay modes often do not agree with simple quark-model expectations.Lattice gauge theories have made strong claims that glueballs and hybrids should appear in the meson spectrum. However, the existence of a scalar glueball, at least with a reasonable width, is highly questionable. It is possible that hybrids will turn up in complex multibody final states even though so far, no convincing case has been made for them by experimental data. Lattice gauge theories fail to identify the nonet of scalar mesons. Thus, at the present status of approximations, lattice gauge theories seem not to provide a trustworthy guide into unknown territory ...

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Section: A Low-mass Nonet Of Scalar Mesonsmentioning

confidence: 99%

Glueballs, hybrids, multiquarks

2007

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“…The quantitative calculations of hadronic properties run into arduous difficulties. However, one can apply the QCD sum rule method [15] (for reviews see [16][17][18][19] and references therein), which is a nonperturbative formulation firmly based on QCD basic theory and has been successfully employed to research some light four-quark states [20][21][22][23][24][25]. In this work, we are devoted to predicting masses of Z + s1 and Z + s2 from QCD sum rules.…”

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confidence: 99%

Search forZs1+andZs2+strangeonium-like structures

2012

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“…We take the updated values of the diquark masses from the QCD sum rules for consistency, where the interpolating currents U a (x), D a (x) and S a (x) are used [31], m Q = 0.46 GeV and m S = 0.40 GeV; the scalar diquarks were originally studied with the QCD sum rules about twenty years ago [32,33]. There have been several theoretical approaches to estimate the diquark masses, for example, the simple constituent diquark mass plus hyperfine spin-spin interaction model [34].…”

Section: Numerical Resultsmentioning

confidence: 99%

Analysis of the Nonet Scalar Mesons as Tetraquark States with New QCD Sum Rules

Wang

2011

Int J Theor Phys

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In this article, we take the scalar diquarks as point particles and describe them as basic quantum fields, then introduce the SU (3) color gauge interaction and new vacuum condensates to study the nonet scalar mesons as tetraquark states with the QCD sum rules. Comparing with the conventional quark currents, the diquark currents have the outstanding advantage to satisfy the two criteria of the QCD sum rules more easily.

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Diquark and light four-quark states

Cited by 46 publications

References 82 publications

Glueballs, hybrids, multiquarks

Glueballs, hybrids, multiquarks

Search forZs1+andZs2+strangeonium-like structures

Analysis of the Nonet Scalar Mesons as Tetraquark States with New QCD Sum Rules

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