The Scalar Meson Sector and the σ, κ Problem

Ochs, Wolfgang

doi:10.1063/1.1799721

Cited by 7 publications

(2 citation statements)

References 31 publications

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“…The corresponding ground state glueball mass predictions are then m (D) S = 1.80 GeV and m (N) S = 1.34 GeV (where m S ≡ m 1 ). The latter is significantly smaller than most quenched lattice results but close to the f (1270) and to results of K-matrix analyses of scalar resonance data [68], mixing schemes with only one 0 ++ multiplet below 1.8 GeV [69], a topological knot model [70] and the QCD sum rule prediction m S = 1.25 ± 0.2 GeV [32]. One might speculate that fixing z −1 m in the flavored meson sector takes some light-quark effects into account and hence corresponds to a lower, unquenched value of the scalar glueball mass (at least under Neumann IR boundary conditions).…”

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confidence: 67%

Holographic glueball structure

Forkel

2008

Phys. Rev. D

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We derive and systematically analyze scalar glueball correlation functions in both the hard-wall and dilaton soft-wall approximations to holographic QCD. The dynamical content of the holographic correlators is uncovered by examining their spectral density and by relating them to the operator product expansion, a dilatational low-energy theorem and a recently suggested two-dimensional power correction associated with the short-distance behavior of the heavy-quark potential. This approach provides holographic estimates for the three lowest-dimensional gluon condensates or alternatively their Wilson coefficients, the two leading moments of the instanton size distribution in the QCD vacuum and an effective UV gluon mass. A remarkable complementarity between the nonperturbative physics of the hard- and soft-wall correlators emerges, and their ability to describe detailed QCD results can be assessed quantitatively. We further provide the first holographic estimates for the decay constants of the 0++ glueball and its excitations. The hard-wall background turns out to encode more of the relevant QCD physics, and its prediction f ~ 0.8-0.9 GeV for the phenomenologically important ground state decay constant agrees inside errors with recent QCD sum rule and lattice results.Comment: 25 pages, discussion extended to match the published version (up to stylistic details), results and conclusions unchange

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confidence: 67%

Holographic glueball structure

Forkel

2008

Phys. Rev. D

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“…Finally, we should comment on the problem of the σ, κ poles whose interpretation as particles remains controversial [56,57]. The evidence has been studied in detail in ππ scattering within a class of parametrizations which respect chiral symmetry and unitarity [58].…”

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confidence: 99%

B decays into light scalar particles and glueball

Minkowski

Ochs

2005

Eur. Phys. J. C

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The recent observations of f 0 (980) in charmless B-decays motivate further studies of scalar particle and glueball production in these processes. Amplitudes for charmless 2-body B decays involving the members of the scalar nonet are presented based on the symmetries of the dominant penguin contribution. Different scenarios for the lightest scalar nonet are investigated in view of the presently available data. We describe the evidence from B-decays for f 0 (1500) with a flavour octet like mixing and the hints towards the members of the q q nonet of lowest mass. There is further support for the hypothesis of a broad 0 ++ glueball acting as coherent background especially in B → KKK. The estimated B decay rates into gluonic mesons represent a sizable fraction of the theoretically derived decay rate for b → sg.

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Direct instantons, topological charge screening, and QCD glueball sum rules

Forkel

2005

Phys. Rev. D

167

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Nonperturbative Wilson coefficients of the operator product expansion (OPE) for the spin-0 glueball correlators are derived and analyzed. A systematic treatment of the direct instanton contributions is given, based on realistic instanton size distributions and renormalization at the operator scale. In the pseudoscalar channel, topological charge screening is identified as an additional source of (semi-) hard nonperturbative physics. The screening contributions are shown to be vital for consistency with the anomalous axial Ward identity, and previously encountered pathologies (positivity violations and the disappearance of the 0 −+ glueball signal) are traced to their neglect. On the basis of the extended OPE, a comprehensive quantitative analysis of eight Borel-moment sum rules in both spin-0 glueball channels is then performed. The nonperturbative OPE coefficients turn out to be indispensable for consistent sum rules and for their reconciliation with the underlying low-energy theorems. The topological short-distance physics strongly affects the sum rule results and reveals a rather diverse pattern of glueball properties. New predictions for the spin-0 glueball masses and decay constants and an estimate of the scalar glueball width are given, and several implications for glueball structure and experimental glueball searches are discussed. I. INTRODUCTIONAmong exotic hadrons, i.e. those which evade classification according to the constituent quark model, glueballs [1, 2, 3] occupy an extreme position. In fact, they contain no valence quarks at all and are the only hadrons which would persist in a world without quarks. Even the exclusion of sea quarks from QCD, as in quenched lattice simulations, is not expected to alter their properties drastically [94]. Hence glueball structure provides a unique source of information on nonperturbative gluon dynamics and may even shed light on the often elusive gluon component of the light classical hadrons (and potentially hybrids). A suggestive way to access this information is to investigate the role of known coherent gluon fields, with instantons as the most prominent example, in glueball structure.The operator product expansion (OPE) [4] of glueball correlation functions provides an effective analytical framework for such investigations. In fact, it exhibits several exceptional features of the gluonium channels already at the qualitative level. The probably most instructive one is directly associated with the defining characteristic of the OPE, i.e. its factorization of the short-distance correlators into contributions from hard and soft field modes. Indeed, since the glueball's gluon content should be mostly nonperturbative, one might expect it to manifest itself primarily in the soft contributions, i.e. in the gluon condensates. Surprisingly, this is not the case: the condensate contributions are unusually weak [5,6,7] and cannot fully reflect the nonperturbative nature of low-lying gluonia. This suggests that a major part of the nonperturbative physics is relatively hard ...

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The Scalar Meson Sector and the σ, κ Problem

Cited by 7 publications

References 31 publications

Holographic glueball structure

Holographic glueball structure

B decays into light scalar particles and glueball

Direct instantons, topological charge screening, and QCD glueball sum rules

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