We show that the latest and very precise dispersive data analyses require a large and very unnat- ural fine-tuning of the 1/Nc expansion at Nc = 3 if the f_0(600) and K(800) light scalar mesons are to be considered predominantly quark-antiquark states, which is not needed for light vector mesons. For this, we use scattering observables whose 1/Nc corrections are suppressed further than one power of 1/Nc for quark-antiquark or glueball states, thus enhancing contributions of other nature. This is achieved without using unitarized ChPT, but if it is used we can also show that it is not just that the coefficients of the 1/Nc expansion are unnatural, but that the expansion itself does not even follow the expected 1/Nc scaling of a glueball or a quark-antiquark meson.
使用Schwinger型质量关系筛选人口过多的等密度张量状态。找到了两种解决方案：一个是胶球是fJ（2220），另一个是胶球分布更广，其中f2（1820）具有最大分量。f2（1565）和fJ（1710）不能被容纳为胶球-（杂化）介子混合物，在没有显着耦合到衰变通道。f2 '（1525）-> pi pi与实验结果一致。fJ（2220）既不民主地衰减味道，也不狭窄。
We discuss the importance of mixing between glueballs -- bound states of gluons -- and excited $\bar{q}q$ states for the glueball search. A preliminary study of the excited states in the Extended Linear Sigma Model (eLSM) suggests their masses in the scalar channel to be in the vicinity of the scalar-glueball mass found in Lattice QCD. This could have implications for future glueball searches.
The vast majority of mesons can be understood as quark-antiquark states. Yet, various other possibilities exists: glueballs (bound-state of gluons), hybrids (quark-antiquark plus gluon), and four-quark states (either as diquark-antidiquark or molecular objects) are expected. In particular, the existence of glueballs represents one of the first predictions of QCD, which relies on the nonabelian feature of its structure; this is why the search for glueballs and their firm discovery would be so important, both for theoretical and experimental developments. At the same time, many new resonances ($…
We present a generalized linear sigma model that includes both scalar and pseudoscalar glueballs in addition to a quark-antiquark as well as a four-quark chiral nonet. Utilizing the axial and trace anomalies of QCD (at the effective mesonic level), we aim to develope the most general structure of the Lagrangian which can be used to study the interaction of quarkonia with glueballs. We then study the effect of scalar glueball on the vacuum of the model by considering a decoupling limit in which the glueball fields are decoupled from quarkonia. This determines the properties of the pure scalar g…
We study the interaction of scalar glueball with quark-antiquark and four-quark spinless meson fields within the framework of a generalized linear sigma model in which the trace anomaly of QCD is exactly realized. To determine the pure scalar glueball mass ($m_h$), we consider the decoupling limit in which the scalar glueball decouples from the meson fields. We find the exact relationship $m_h = 2\, h_0$ where $h_0$ is the vacuum expectation value of the scalar glueball field independent of the properties of the framework used.
We study the quark-antiquark scattering phase shift and meson spectral function in the pion superfluid described by the Nambu--Jona-Lasinio model. The meson mixing in the pion superfluid changes dramatically the full scattering phase shift and spreads strongly the spectral function of some of the collective modes.
The mixing angles between scalar isoscalar resonances and a scalar glueball are determined from their decays into two pseudoscalar mesons. For $f_0(1370)$ and $f_0(1500)$, at most a small glueball component is admitted by the data. The decay modes of $f_0(1710)$, $f_0(1770)$, $f_0(2020)$, and $f_0(2100)$ require significant glueball fractions. Above this mass, the errors in the decay frequencies become too large to extract a glueball component. The summation of all observed glueball fractions up to 2100\,MeV yields (78\er18)\%. The glueball fractions as function of the mass are consistent with…
We solve a Minkowski-space integral equation, derived in the Covariant Spectator Theory, for quark-antiquark bound states describing heavy and heavy-light mesons. The equation's kernel contains a one-gluon exchange interaction and a covariant generalization of a linear confining potential with a mixed scalar, pseudoscalar, and vector Lorentz structure, characterized by a continuous mixing parameter. We investigate to what extent the Lorentz structure of the confining kernel can be determined by fitting the mixing parameter to the meson spectrum.
This compact review about gluonium focuses on a slate of theoretical efforts; among the many standing works, I have selected several that are meant to assist in the identification, among ordinary mesons, of the few Yang-Mills glueball configurations that populate the energy region below 3 GeV. This includes $J/ψ$ radiative and vector-meson decays, studies of scalar meson mixing, of high-energy cross sections via the Pomeron and the odderon, glueball decays, etc. The weight of accumulated evidence seems to support the $f_0(1710)$ as having a large (and the largest) glueball component among the …
We study the vacuum properties of the pseudoscalar glueball and charmed mesons by using the so-called extended Linear Sigma Model (eLSM). This model includes scalar and pseudoscalar mesons, as well as vector and axial-vector mesons. We calculate the mesonic and baryonic decays of the pseudoscalar glueball, where we fixed its mass to $2.6$ GeV, as predicted by lattice-QCD simulations, and take a closer look at the scalar-isoscalar decay channel. As a second step, we enlarge the so-called extended linear Sigma model (eLSM) by including the charm quark to a global $U(4)_r\times U(4)_l$ chiral sym…
In this study we present a unified phenomenological analysis of the scalar glueball and scalar meson spectra within an AdS/QCD framework in the bottom up approach. For this purpose we generalize the recently developed graviton soft-wall (GSW) model, which has shown an excellent agreement with the lattice QCD glueball spectrum, to a description of glueballs and mesons with a unique energy scale. In this scheme, dilatonic effects, are incorporated in the metric as a deformation of the AdS space. We apply the model also to the heavy meson spectra with success. We obtain quadratic mass equations f…
We revisit the mixing mechanism for pesudscalar mesons and glueball which is introduced by the axial vector anomaly. We demonstrate that the physical mass of the pseudoscalar glueball does not favor to be lower than 1.8 GeV if all the parameters are reasonably constrained. This conclusion, on the one hand, can accommodate the pseudoscalar glueball mass calculated by Lattice QCD, and on the other hand, is consistent with the high-statistics analyses at BESIII that all the available measurements do not support the presence of two closely overlapping pseudoscalar states in any exclusive channel. …
We expand the study of the pseudoscalar glueball and its first excited state by constructing an interaction Lagrangian which produces the two- and three-body decays of the pseudoscalar glueball, $J^{PC}=0^{-+}$, into the (pseudo)scalar and the excited (pseudo)scalar mesons as well as by constructing other two different chiral Lagrangians which describe the two- and three-body decays of the first excited pseudoscalar glueball, $J^{PC}=0^{*-+}$, into the (pseudo)scalar and the excited (pseudo)scalar mesons. We compute the decay channels for the ground state of a pseudoscalar glueball with a mass…
Two interconnected fields of interest are suggested for NICA. Firstly, existence of glueballs is predicted by the theory of strong interaction but -- even after decades of research -- glueball identification in the physical spectrum is still unclear. NICA can help to ascertain experimental glueball candidates via J/Psi decays whose yield is expected to be large. Importance of glueballs is not limited to vacuum: since they couple to other meson states, glueballs can also be expected to influence signatures of chiral-symmetry restoration in the high-energy phase of strong dynamics. Mass shifting…
A phenomenological analysis of the scalar glueball and scalar meson spectra is carried out by using the AdS/QCD framework in the bottom-up approach. The resulting spectra are in good agreement for glueballs with lattice QCD results and for mesons with PDG data. We make use of the relation between the mode functions in AdS/QCD and the wave functions in Light-Front $QCD$ to discuss the mixing of glueballs and mesons. The results of our investigation point out that above 2 GeV scalar particles will appear in almost degenerate pairs of unmixed glueball and mesons states leading to an interesting p…
The graviton soft wall model (GSW) provides a unified description of the scalar glueball and meson spectra with a unique energy scale. This success has led us to extend the analysis to the description of the spectra of other hadrons. We use this model to calculate masses of the odd and even ground states of glueballs for various spins, and show that the GSW model is able to reproduce the Regge trajectory of these systems. In addition, the spectra of the $ρ$, $a_1$ and the $η$ mesons will be addressed. Results are in excellent agreement with current experimental data.Furthermore such an achieve…
