Topological charge screening and pseudoscalar glueballs

Forkel, Hilmar

doi:10.1590/s0103-97332004000500045

Cited by 4 publications

(3 citation statements)

References 12 publications

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“…[19]. However, this state lies considerably lower than the theoretical expectations: the lattice QCD predictions suggest a glueball around 2.5 GeV [36,59]; the mass scale of the pseudoscalar glueball obtained in the QCD sum rule approach is above 2 GeV [7,15,16,60]. Moreover, there are attractive arguments for the scalar and pseudoscalar glueballs being approximately degenerate in mass [61], and even the scenario that a pseudoscalar glueball may be lower in mass than the scalar one was recently discussed in Ref.…”

Section: Conclusion and Discussionmentioning

confidence: 91%

Finite-width Laplacian sum rules for 2++ tensor glueball in the instanton vacuum model

Chen

Liu

2017

Phys. Rev. D

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The more-carefully defined, and more appropriate 2 ++ tensor glueball current is a SUc(3) gaugeinvariant, symmetric, traceless and conserved Lorentz-irreducible tensor. After Lorentz decomposition, the invariant amplitude of the correlation function is abstracted, and calculated based on the semiclassical expansion for quantum chromodynamics (QCD) in the instanton liquid background. Besides taking the perturbative contribution into account, we calculate the contribution arising from the interaction (or the interference) between instantons and the quantum gluon fields, which is infrared free. Instead of the usual zero-width approximation for the resonances, the Breit-Wigner form with a correct threshold behavior for the spectral function of the finite-width three resonances is adopted. The properties of the 2 ++ tensor glueball are investigated via a family of the QCD Laplacian sum rules for the invariant amplitude. The values of the mass, decay width and coupling constants for the 2 ++ resonance in which the glueball fraction is dominant are obtained.

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Section: Conclusion and Discussionmentioning

confidence: 91%

Finite-width Laplacian sum rules for 2++ tensor glueball in the instanton vacuum model

Chen

Liu

2017

Phys. Rev. D

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show abstract

“…[13]. However, this state lies considerably lower than the theoretical expectations: the lattice QCD predictions suggest a glueball around 2.5GeV [44,45]; the mass scale of the pseudoscalar glueball obtained in the QCD sum rule approach is above 2GeV [37,38,40,7]. On the other hand, there are attractive arguments for the approximately degenerate in mass for the scalar and pseudoscalar glueballs [46], and even the scenario that a pseudoscalar glueball may be lower in mass than the scalar one is recently discussed in Ref.…”

Section: Introductionmentioning

confidence: 79%

“…An other serious problem in the 0 −+ glueball sum rule approach is that the fundamental spectral positivity bound is violated when including the strong repulsive pure instanton contribution, and as a consequence, the signal for the pseudoscalar glueball disappears [39]. To cure this pathology of positivity violation, the topological charge screening effect in the QCD vacuum is added to the correlation function, and a suitable instanton size distribu-tion is taken into account [40,7]. However, as comparing with the interference contribution, which we have recalculated in this paper, and the pure perturbative one in the considered energy region, the topological screening effect turns out to be negligible; and the pathology of positivity violation disappears when including the interference contribution (s. below).…”

Section: Introductionmentioning

confidence: 99%

Finite-width Gaussian sum rules for $$0^{-+}$$ 0 - + pseudoscalar glueball based on correction from instanton–gluon interference to correlation function

2015

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Based on a correction from instanton-gluon interference to the correlation function, the properties of the 0 −+ pseudoscalar glueball are investigated in a family of finite-width Gaussian sum rules. In the framework of a semiclassical expansion for quantum chromodynamics in the instanton liquid background, the contribution arising from the interference between instantons and the quantum gluon fields is calculated, and it is included in the correlation function together with a pure-classical contribution from instantons and the perturbative one. The interference contribution turns out to be gauge-invariant, to be free from an infrared divergence, and to have a great role to play in restoring the positivity of the spectra of the full correlation function. The negligible contribution from vacuum condensates is excluded in our correlation function to avoid double counting. Instead of the usual zero-width approximation for the resonances, the usual Breit-Wigner form with a suitable threshold behavior for the spectral function of the finite-width resonances is adopted. Consistency between the subtracted and unsubtracted sum rules is very well justified. The values of the mass, decay width, and coupling constants for the 0 −+ resonance in which the glueball fraction is dominant are obtained, and they agree with the phenomenological analysis.

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Vacuum structure and string tension in Yang-Mills dimeron ensembles

2012

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We numerically simulate ensembles of SU(2) Yang-Mills dimeron solutions with a statistical weight determined by the classical action and perform a comprehensive analysis of their properties. In particular, we examine the extent to which these ensembles capture topological and confinement properties of the Yang-Mills vacuum. This further allows us to test the classic picture of meron-induced quark confinement as triggered by dimeron dissociation. At small bare couplings, spacial, topological-charge and color correlations among the dimerons generate a short-range order which screens topological charges. With increasing coupling this order weakens rapidly, however, in part because the dimerons gradually dissociate into their meron constituents. Monitoring confinement properties by evaluating Wilson-loop expectation values, we find the growing disorder due to these progressively liberated merons to generate a finite and (with the coupling) increasing string tension. The short-distance behavior of the static quark-antiquark potential, on the other hand, is dominated by small, "instanton-like" dimerons. String tension, action density and topological susceptibility of the dimeron ensembles in the physical coupling region turn out to be of the order of standard values. Hence the above results demonstrate without reliance on weak-coupling or low-density approximations that the dissociating dimeron component in the Yang-Mills vacuum can indeed produce a meron-populated confining phase. The density of coexisting, hardly dissociated and thus instanton-like dimerons seems to remain large enough, on the other hand, to reproduce much of the additional phenomenology successfully accounted for by non-confining instanton vacuum models. Hence dimeron ensembles should provide an efficient basis for a rather complete description of the Yang-Mills vacuum.Comment: 36 pages, 17 figure

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Topological charge screening and pseudoscalar glueballs

Cited by 4 publications

References 12 publications

Finite-width Laplacian sum rules for 2++ tensor glueball in the instanton vacuum model

Finite-width Laplacian sum rules for 2++ tensor glueball in the instanton vacuum model

Finite-width Gaussian sum rules for $$0^{-+}$$ 0 - + pseudoscalar glueball based on correction from instanton–gluon interference to correlation function

Vacuum structure and string tension in Yang-Mills dimeron ensembles

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