The Physics of Glueballs

Abstract

Glueballs are particles whose valence degrees of freedom are gluons and therefore in their description the gauge field plays a dominant role. We review recent results in the physics of glueballs with the aim set on phenomenology and discuss the possibility of finding them in conventional hadronic experiments and in the Quark Gluon Plasma. In order to describe their properties we resort to a variety of theoretical treatments which include, lattice QCD, constituent models, AdS/QCD methods, and QCD sum rules. The review is supposed to be an informed guide to the literature. Therefore, we do not discuss in detail technical developments but refer the reader to the appropriate references.

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

“…(c) The results in QCD-based constituent models are controversial from each other, the lowest lying 2 ++ glueball lies in the mass region of 0.96 − 2.5 GeV [55], and our prediction is located in between.…”

“…[55] by the variational procedure in Monte-Carlo simulations [36], however, the mass of the lowest-lying glueball should be understood as the upper bound of the glueball in the channel of interest. It is important to note that our result in this work is to confront with the reality case.…”

“…Later, in the mass region of the first radial excitation of the η and η ′ mesons, a supernumerous candidate, the η(1405) has been observed. It seems to be clear that η(1405) is allowed as a glueball dominated state mixed with isoscalar qq states due to its behavior in production and decays, namely, it has comparably large branching ratios in the J/ψ radiativedecay, but it has not been observed in γγ collisions [19,55,58]. A review on the experimental status of the qq is given in Ref.…”

“…The resonance masses and widths appearing in (50) could be estimated by matching both sides of sum rules (55) optimally in the fiducial domain (sum rule window) where the mentioned resonance parameters should approximately be stable. At t max of the sum rule window, the resonance contribution should be great than the continuum one…”

Dalitz plot analysis ofηc→K+K−ηandLees1, Poireau2, Tisserand3 et al. 2014Phys. Rev. D

“…One of the motivations for these studies is the search for non-qq mesons such as glueballs or molecular states that are predicted by QCD to populate the low mass region of the hadron mass spectrum [3]. Recently, a search for exotic resonances was performed through Dalitz plot analyses of χ c1 states [4].…”