Evidence for a 1−+ exotic meson

Alde, D.; Knapp, Edward E.A.; Binon, Freddy; Bricman, C.; Lagnaux, Jean-Pierre; Stroot, Jean-Pierre; Boutemeur, M.; Gouanère, M.; Massonnet, L.; Peigneux, Jean Pierre; Donskov, Sergey; Inyakin, Alexandre A.V.; Kachanov, Vasilij V.A.; Kakauridze, D.B.; Khaustov, G.V.; Lednev, A.A.; Obraztsov, V.; Prokoshkin, Yu Y.D.; Rodnov, Yu Y.V.; Sadovsky, Sergey S.A.; Samoylenko, V.D.; Shagin, Petr P.M.; Shtannikov, A.V. A.V.; Singovsky, Alexandre A.V.; Sugonyaev, V.P.

doi:10.1016/0370-2693(88)91686-3

Cited by 169 publications

(32 citation statements)

References 13 publications

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“…Z: The kaon K was already mentioned; the K 2 (1770) was discovered as L(1770) [86]. The M(1405) was a precursor of the 1 (1400) [87]. The N and P are reserved for neutron/nucleon and proton, the O is void.…”

Section: A Guide To the Literaturementioning

confidence: 96%

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 Guide To the Literaturementioning

confidence: 96%

Glueballs, hybrids, multiquarks

2007

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“…Experimentally, there are two candidates for the 1 −+ -one is π 1 (1400) [29] and the other is π 1 (1600) [30]. They are observed in the ηπ and ρπ channels.…”

Section: Meson a Hybrid? 1 Introductionmentioning

confidence: 99%

Is the1−+meson a hybrid?

Yang

Chen

et al. 2012

Phys. Rev. D

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We calculate the vacuum to meson matrix elements of the dimension-4 operatorψγ 4 ← → D i ψ and dimension-5 operatorψε ijk γ j ψB k of the 1 −+ meson on the lattice and compare them to the corresponding matrix elements of the ordinary mesons to discern if it is a hybrid. For the charmoniums and strange quarkoniums, we find that the matrix elements of 1 −+ are comparable in size as compared to other known qq mesons. They are particularly similar to those of the 2 ++ meson, since their dimension-4 operators are in the same Lorentz multiplet. Based on these observations, we find no evidence to support the notion that the lowest 1 −+ mesons in the cc and ss regions are hybrids. As for the exotic quantum number is concerned, the non-relativistic reduction reveals that the leading terms in the dimension-4 and dimension-5 operators of 1 −+ are identical up to a proportional constant and it involves a center-of-mass momentum operator of the quark-antiquark pair. This explains why 1 −+ is an exotic quantum number in the constituent quark model where the center of mass of the qq is not a dynamical degree of freedom. Since QCD has gluon fields in the context of the flux-tube which is appropriate for heavy quarkoniums to allow the valence qq to recoil against them, it can accommodate such states as 1 −+ . By the same token, hadronic models with additional constituents besides the quarks can also accommodate the qq center-of-mass motion. To account for the quantum numbers of these qq mesons in QCD and hadron models in the non-relativistic case, the parity and total angular momentum should be modified to P = (−) L+l+1 and J = L + l + S, where L is the orbital angular momentum of the qq pair in the meson.

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“…There are several experimental candidates for H : the π 1 (1400), seen at GAMS [82], E852 [83], Crystal Barrel [84,85], VES [86], the π 1 (1600), seen at E852 [87][88][89][90][91], Crystal Barrel [92], VES [86,[93][94][95], most recently confirmed by COMPASS [96], and the π 1 (2000) [90,91].…”

Section: Electroproduction Of An Exotic Hybrid Mesonmentioning

confidence: 98%

A Short Review of the Theory of Hard Exclusive Processes

Wallon

2012

Few-Body Syst

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We first present an introduction to the theory of hard exclusive processes. We then illustrate this theory by a few selected examples. The last part is devoted to the most recent developments in the asymptotical energy limit. Introduction Hard Processes in QCDQuantum chromodynamics (QCD) is the theory of strong interaction, one of the four elementary interactions of the universe. It is a relativistic quantum field theory of Yang-Mills type, with the SU (3) gauge group. The quark and gluon elementary fields are confined inside hadrons. Nevertheless, they can be expressed as superpositions of Fock states:-mesons (π, η, f 0 , ρ, ω . . .): |qq + |qqg + |qqqq + · · · -baryons ( p, n, N , . . .): |qqq + |qqqg + |qqqqq + · · · In contrast with electrodynamics, strong interaction increases with distance, or equivalently decreases when energy increases. This phenomenon, called asymptotical freedom, means that the coupling satisfies α s (Q) 1 for Q QC D 200 MeV. The natural question which then arises is how to describe and understand the internal structure of hadrons, starting from their elementary constituents, despite the confinement. In the non-perturbative domain, the two available tools are: -Chiral perturbation theory: systematic expansion based on the fact that u and d quarks have a very small mass, the π mass being an expansion parameter outside the chiral limit (in which these mass would be set to zero). -Discretization of QCD on a 4-d lattice, leading to numerical simulations.Other analytical tools have been proposed recently, among which is the AdS/QCD correspondence, a phenomenological extension of the AdS/CFT correspondence.Besides these tools, one may wonder whether it is possible to extract informations reducing the process to interactions involving a small number of partons (quarks, gluons), despite confinement. This is possible if the considered process is driven by short distance phenomena, with typical distances between the interacting partons much less than 1 fm, i.e. for α s 1. This is the underlying principle of perturbative methods.

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Evidence for a 1−+ exotic meson

Cited by 169 publications

References 13 publications

Glueballs, hybrids, multiquarks

Glueballs, hybrids, multiquarks

Is the1−+meson a hybrid?

A Short Review of the Theory of Hard Exclusive Processes

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