Casimir scaling, glueballs, and hybrid gluelumps

Mathieu, V.; Semay, Claude; Brau, Fabian

doi:10.1140/epja/i2005-10251-7

Cited by 30 publications

(50 citation statements)

References 34 publications

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“…For further developments, it is useful to briefly sum up the key points of this last reference. Assuming the Casimir scaling hypothesis, it can be shown that the flux tubes in a qqg system are two fundamental straight strings linking the gluon to the quark and to the antiquark [7], in agreement with refs. [5,9].…”

supporting

confidence: 89%

“…This picture has been firstly studied in refs. [ but also in more recent works including effective models as well as lattice QCD calculations [6][7][8][9]. Very good descriptions of mesons and baryons, even light ones, are obtained within the framework of potential models with constituent quarks.…”

mentioning

confidence: 99%

“…Let us begin with the ccg hybrid, for which we use the parameters of ref. [7]: m c = 1.3 GeV and a = 0.175 GeV 2 . These values are fitted so that the mass of the J/Ψ -meson is correctly reproduced as well as the Regge slope of the ρ-meson family.…”

mentioning

confidence: 99%

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Excited flux tube from q¯g hybrid mesons

et al. 2007

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Abstract. In the framework of quark models, hybrid mesons are either seen as two-body qq systems with an excited flux tube connecting the quark to the antiquark or as three-body qqg systems including a constituent gluon. In this work we show that, starting from the three-body wave function of the qqg hybrid meson in which the gluonic degrees of freedom are averaged, the excited flux tube picture emerges as an equivalent qq potential. This equivalence between the excited flux tube and the constituent-gluon approach is confirmed for heavy hybrid mesons but, for the first time, it is shown to hold in the light sector too, provided the contribution of the quark dynamics is correctly taken into account. The study of hybrid mesons is an active domain in theoretical and in experimental particle physics with future experiments BESIII, GLUEX and PANDA. From a theoretical point of view, they are interpreted as mesons in which the color field is in an excited state. Numerous lattice QCD calculations have been devoted to hybrid mesons [1,2], as well as many studies involving effective models. In particular, within the framework of quark models, there are two main approaches. In the first one, the quark and the antiquark are linked by a string, or flux tube, which is responsible for the confinement. In this stringy picture, it is possible for the flux tube to fluctuate, and thus to be in an excited state [3,4]. The second approach assumes that the hybrid meson is a three-body system formed of a quark, an antiquark, and a constituent gluon. Two straight strings then link the gluon to the quark and to the antiquark. This picture has been firstly studied in refs. but also in more recent works including effective models as well as lattice QCD calculations [6][7][8][9]. Very good descriptions of mesons and baryons, even light ones, are obtained within the framework of potential models with constituent quarks. Moreover, it has been recently shown that such models, with constituent gluons, give gg and ggg glueball spectra very similar to results predicted by lattice QCD works [10]. This picture of constituent particles is also validated by recent lattice calculations [9]. So it seems relevant to work in this framework. PACSIt was suggested in ref.[8] that, in the static quark limit, the constituent-gluon picture is equivalent to the excited flux tube one, the total energy of the constituent gluon being equal to the energy contained in the excited string. These results were extended in ref. [11], where the dynamics of the quarks has been taken into account. For further developments, it is useful to briefly sum up the key points of this last reference. Assuming the Casimir scaling hypothesis, it can be shown that the flux tubes in a qqg system are two fundamental straight strings linking the gluon to the quark and to the antiquark [7], in agreement with refs. [5,9].In this work, in order to simplify, we will neglect all short-range interactions between quarks and gluon and only consider the dominant confining potential. In this

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confidence: 89%

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confidence: 99%

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Excited flux tube from q¯g hybrid mesons

et al. 2007

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“…[5,12], and will be further developed in sec. IV C. Let us note that the same argument holds in the case of the massless u and d quarks, whose constituent mass is around 0.3 GeV [14].…”

Section: B Gluonsmentioning

confidence: 60%

“…m has thus here to be understood as the constituent gluon mass in a particular bound state, which typically has a value around 0.5 − 0.6 GeV [14,23]. This argument has already been used in refs.…”

Section: B Gluonsmentioning

confidence: 98%

Short-range potentials from QCD at orderg²

Mathieu¹,

Buisseret²

2008

J. Phys. G: Nucl. Part. Phys.

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We systematically compute the effective short-range potentials arising from second order QCDdiagrams related to bound states of quarks, antiquarks, and gluons. Our formalism relies on the assumption that the exchanged gluons are massless, while the constituent gluons as well as the lightest quarks acquire a nonvanishing constituent mass because of confinement. We recover the well-known Fermi-Breit interaction in the heavy quark limit. Such an effective potential has been proved in the past to be relevant for the building of accurate potential models describing usual hadrons (mesons and baryons). The general potentials we obtain in this work are also expected to be useful in the understanding of exotic hadrons like glueballs and qqg hybrids. In particular, we compute for the first time an effective short-range quark-gluon potential, and show the existence of a quadrupolar interaction term in this case. We also discuss the influence of a possible nonzero mass for the exchanged gluons.

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