Exotic<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow><mml:mi>ρ</mml:mi></mml:mrow><mml:mrow><mml:mo>±</mml:mo></mml:mrow></mml:msup></mml:mrow><mml:mrow><mml:msup><mml:mrow><mml:mi>ρ</mml:mi></mml:mrow><mml:mrow><mml:mn>0</mml:mn></mml:mrow></mml:msup></mml:mrow></mml:math>state photoproduction

Achasov, N. N.; Shestakov, G. N.

doi:10.1103/physrevd.60.114021

Cited by 7 publications

(9 citation statements)

References 99 publications

(65 reference statements)

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“…The existence of tetraquark states with I = 0 and 2 and their destructive interference in → + − and constructive interference in → 0 0 was predicted a long time ago by Achasov, Devyanin and Shestakov [974] and by Li and Liu [975]. The data were thus be claimed to prove the existence of tetraquark isotensor resonances at M ≈ 1600 MeV/c 2 , ≈ 500 MeV/c 2 [976][977][978]. Calculations within QCD sum rules [979] do no exclude such resonances.…”

Section: Isospin Exoticsmentioning

confidence: 87%

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: Isospin Exoticsmentioning

confidence: 87%

Glueballs, hybrids, multiquarks

2007

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“…Also the a 0 πη coupling is very sensitive to loop corrections due to the K K threshold. σ → π + π − + π 0 π 0 2.17 1.95 [11] 574 300-1000 [3] σ → K + K − + K 0 K0 0.16 0.004 [11] 0 0 f 0 → π + π − + π 0 π 0 1.67 0.765 +0.20 −0.14 [12] see text 40 -100 [3] f 0 → K + K − + K 0 K0 6.54 4.26 1.78 −1.12 [12] 0 0 a + 0 → π + η 2.29 0.57 [12] 273 see text 50 -100 [3] a + 0 → K + K0 2.05 1.34 +0.36 −0.28 [12] 0 0…”

Section: Discussionmentioning

confidence: 99%

“…In some of the channels of table II the resonance is below threshold and the widths therefore vanish at the resonance mass. However, the coupling constants have recently been determined through a loop diagram from φ → K K → γππ and φ → K K → γπη (albeit in a somewhat model dependent way) by the Novosibirsk group [11,12]. For channels where the phase space is large, it is important that one includes a form factor related to the finite size of physical mesons.…”

Section: Tri-linear Couplings At the Tree Levelmentioning

confidence: 99%

Comparing the broken $U3 \times U3$ linear sigma model with experiment

Törnqvist

1999

Eur. Phys. J. C

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The linear σ model with broken U3×U3 is compared with data on the lightest scalar and pseudoscalar mesons. When 5 of the 6 parameters are fixed by the pseudoscalar masses and decay constants one finds that, already at the tree level, a reasonable description for the 4 scalar masses, mixing and up to 8 trilinear couplings of lightest scalars, taken as a 0 (980), f 0 (980), σ(≈ 500) and K * 0 (1430). This clearly indicates that these scalars are the chiral partners of the π, η, η ′ , K and strongly suggests that they like the latter are (unitarized) qq states.

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“…The a 1 exchange for the reaction πp → (ππ) S n was considered in [10,54]. In [10], the calculations of the ππ spectra were performed both with the a 1 exchange and within an effective π exchange.…”

Section: Peripheral Two-meson Production In Meson-nucleon Collisions mentioning

confidence: 99%

Systematics of quark–antiquark states and scalar exotic mesons

Anisovich¹

2004

Phys.-Usp.

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The analysis of the experimental data of Crystal Barrel Collaboration on the pp annihilation in flight with the production of mesons in the final state resulted in a discovery of a large number of mesons over the region 1900-2400 MeV, thus allowing us to systematize quark-antiquark states in the (n, M 2 ) and (J, M 2 ) planes, where n and J are radial quantum number and spin of the meson with the mass M . The data point to meson trajectories in these planes being approximately linear, with a universal slope. The sector of scalar mesons is discussed in more detail, where, on the basis of the recent K-matrix analysis, the nonet classification of quark-antiquark states was performed: in the region below 2000 MeV, two scalar nonets are fixed, that is, the basic one and the nonet of the first radial excitation. In the scalar sector, there are two states with the isospin

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Exoticρ±ρ0state photoproduction

Cited by 7 publications

References 99 publications

Glueballs, hybrids, multiquarks

Glueballs, hybrids, multiquarks

Comparing the broken $U3 \times U3$ linear sigma model with experiment

Systematics of quark–antiquark states and scalar exotic mesons

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