Glueball Candidate Research Articles

Decays of the tensor glueball in a chiral approach

Glueballs remain an experimentally undiscovered prediction of QCD. Lattice QCD predicts a spectrum of glueballs, with the tensor (JPC = 2++) glueball being the second lightest, behind the scalar glueball. From an effective hadronic model based on spontaneous and explicit chiral symmetry breaking, we compute decay ratios of the tensor glueball into various meson decay chan nels. We find the tensor glueball to primarily decay into 2 vector mesons, dom inated by ρρ and K* K*. These results are compared to experimental data of decay rates of spin 2 mesons. Based on this comparison we make statements on the eligibility of these mesons as potential tensor glueball candidates.

Radiative meson and glueball decays in the Witten-Sakai-Sugimoto model

We calculate radiative decay rates of mesons and glueballs in the top-down holographic Witten-Sakai-Sugimoto model with finite quark masses. After assessing to what extent this model agrees or disagrees with experimental data, we present its predictions for so far undetermined decay channels. Contrary to widespread expectations, we obtain sizeable two-photon widths of scalar, tensor, and pseudoscalar glueballs, suggesting in particular that the observed two-photon rate of the glueball candidate ${f}_{0}(1710)$ is not too large to permit a glueball interpretation, but could be even much higher. We also discuss the so-called exotic scalar glueball, which in the Witten-Sakai-Sugimoto model is too broad to match either of the main glueball candidates ${f}_{0}(1500)$ and ${f}_{0}(1710)$ but might be of interest with regard to the alternative scenario of the so-called fragmented scalar glueball. Employing the exotic scalar glueball for the latter, much smaller two-photon rates are predicted for the ground-state glueball despite a larger total width; relatively large two-photon rates would then apply to the excited scalar glueball described by the predominantly dilatonic scalar glueball. In either case, the resulting contributions to the muon $g\ensuremath{-}2$ from hadronic light-by-light scattering involving glueball exchanges are small compared to other single meson exchanges, of the order of $\ensuremath{\lesssim}{10}^{\ensuremath{-}12}$.

Repercussion of the [formula omitted] [[formula omitted]] resonance and future developments

In this paper, we discuss the significance and prospect for the newly discovered a0(1710)[a0(1817)] resonance state at BESIII experiment, in which they reported the observation of a scalar meson of spin-parity $J^P=0^+$ with isospin $I=1$, branded as $a_0(1817)$. This state may be the same particle as the $a_0(1710)$ observed by the BaBar experiment earlier. As early as 2008, we found that f0(1710) can be regarded as a $K^* \bar{K}^*$ molecular state based on the chiral unitary theory, and there is a partner state $a_0(1710)$ with an isospin $I=1$. Our theoretical prediction based on this picture is in good agreement with the latest BESIII data, which further supports the molecular state picture of $a_0(1710)[a_0(1817)]$. If it is indeed the isospin partner state of $f_0(1710)$, this would rule out $f_0(1710)$ as a glueball candidate. This paper briefly reviews the relevant theoretical studies and suggests new experiments to further examine the nature of $a_0(1710)[a_0(1817)]$.

Nature of X(2370)

We address the nature of the $X(2370)$ resonance observed in the $J/\psi$ radiative decays, $J/\psi\rightarrow\gamma K^{+} K^{-}\eta'$, $J/\psi\rightarrow\gamma K_S K_S\eta'$ and $J/\psi\rightarrow\gamma \pi^{+}\pi^{-}\eta'$. By studying the invariant mass spectra we confirm that decays of the $X(2370)$ into three pseudo-scalars are well described by an effective chiral Lagrangian. We extract the branching ratio of $J/\psi\to X(2370)\gamma$ and show that it is an order of magnitude larger compared to the glueball production rate predicted by lattice QCD. This indicates that $X(2370)$ is not likely to be a glueball candidate.

Scalar and tensor resonances in J/psi radiative decays

We perform a systematic analysis of the J/psi rightarrow gamma pi ^0pi ^0 and rightarrow gamma K_S^0 K_S^0 partial waves measured by BESIII. We use a large set of amplitude parametrizations to reduce the model bias. We determine the physical properties of seven scalar and tensor resonances in the 1–2.5 , {mathrm {GeV}} mass range. These include the well known f_0(1500) and f_0(1710), that are considered to be the primary glueball candidates. The hierarchy of resonance couplings determined from this analysis favors the latter as the one with the largest glueball component.

Recent results on branching fraction and CP asymmetry in B → ϕϕK decays

We present precise measurements of the branching fraction and CP-violation asymmetry in the B meson system, specifically in the charmless decays B → ϕϕK, ϕ → K+K−. This study is based on the full ϒ(4S) data set of 772×106BB‾ pairs collected by the Belle detector at KEKB asymmetric energy e+e− collider. These decays are mediated by the b → s flavor-changing neutral current (FCNC) transition, which could exhibit large CP violations due to interference of potential new-physics amplitudes appearing in the quantum loop with the b → c tree-level transition of B → ηcK, ηc → ϕϕ. Therefore, an observation of direct CP violation in B → ϕϕK decays would be a clear sign of physics beyond the standard model. In addition to being an NP probe, the decay is sensitive to possible production of glue-ball candidate that later decays as ξ → ϕϕ. Our results obtained with nine times larger statistics and refined analysis techniques significantly improve upon, and supersede, the Belle's earlier result with due consideration of the nonresonant K+K− contribution underneath the ϕ resonance.

Holographic description of heavy-flavored baryonic matter decay involving glueball

We holographically investigate the decay of heavy-flavoured baryonic hadron involving glueball by using the Witten-Sakai-Sugimoto model. Since baryon in this model is recognized as the D4-brane wrapped on $S^{4}$ and the glueball field is identified as the bulk gravitational fluctuations, the interaction of the bulk graviton and the baryon brane could be naturally interpreted as glueball-baryon interaction through the holography which is nothing but the close-open string interaction in string theory. In order to take account into the heavy flavour, an extra pair of heavy-flavoured branes separated from the other flavour branes with a heavy-light open string is embedded into the bulk. Due to the finite separation of the flavour branes, the heavy-light string creates massive multiplets which could be identified as the heavy-light meson fields in this model. As the baryon brane on the other hand could be equivalently described by the instanton configuration on the flavour brane, we solve the equations of motion for the heavy-light fields with the Belavin-Polyakov-Schwarz-Tyupkin (BPST) instanton solution for the $N_{f}=2$ flavoured gauge fields. Then with the solutions, we evaluate the soliton mass by deriving the flavoured onshell action in strongly coupling limit and heavy quark limit. After the collectivization and quantization, the quantum mechanical system for glueball and heavy-flavoured baryon is obtained in which the effective Hamiltonian is time-dependent. Finally we use the standard technique for the time-dependent quantum mechanical system to analyze the decay of heavy-flavoured baryon involving glueball and we find one of the decay process might correspond to the decay of baryonic B-meson involving the glueball candidate $f_{0}\left(1710\right)$. This work is a holographic approach to study the decay of heavy-flavoured hadron in nuclear physics.

Revisiting the pseudoscalar meson and glueball mixing and key issues in the search for a pseudoscalar glueball state

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. Such a result is in agreement with the recent claim that the slightly shifted peak positions for two possible states $\eta(1405)$ and $\eta(1475)$ observed in different channels are actually originated from one single state with the triangle singularity interferences. By resolving this long-standing paradox, one should pay more attention to higher mass region for the purpose of searching for the pseudoscalar glueball candidate.

Light Hadron Spectroscopy at BESIII

The BESIII has collected 1.3 billion J/ψ and 478 million ψ(3686) data since 2009. In this talk, we will introduce five recent analyses on light hadron spectroscopy at BESIII, including two studies on the X(1835), two partial wave analyses that are related to searching and studying glueball candidates, and one study on χc1.

Holographic QCD predictions for production and decay of pseudoscalar glueballs

The top–down holographic Witten–Sakai–Sugimoto model for low-energy QCD, augmented by finite quark masses, has recently been found to be able to reproduce the decay pattern of the scalar glueball candidate f0(1710) on a quantitative level. In this Letter we show that this model predicts a narrow pseudoscalar glueball heavier than the scalar glueball and with a very restricted decay pattern involving η or η′ mesons. Production should be either in pairs or in association with η(′) mesons. We discuss the prospect of discovery in high-energy hadron collider experiments through central exclusive production by comparing with η′ pair production.

X(1835) Decay in the Fock-Tani Formalism

In this work we have obtained an effective Hamiltonian to describe the strong decay of pseudoscalar glueball, where the microscopic interaction between the constituent gluons have been taking into account. The pseudoscalar glueball candidate we have considered here is the [Formula: see text] resonance. In our calculation the [Formula: see text] was a pure glueball.

Pomeron interactions from the Einstein-Hilbert action

Holographic models of QCD, collectively known as AdS/QCD, have been proven useful in deriving several properties of hadrons. One particular feature well reproduced by such models is the Regge trajectories, both for mesons and glueballs. We focus on scalar and tensor glueballs, and derive an effective theory for the Pomeron by analytic continuation along the leading trajectory from the tensor glueball. It then follows that the Pomeron, as the tensor glueball itself, should possess a two-index polarization tensor, inherited from the graviton. The three-graviton interaction is deduced from the Einstein-Hilbert action. Using this structure in the cross section of double-Pomeron production of the tensor glueball, we calculate certain angular distributions of production and compare them with those from the CERN WA102 experiment. We find that the agreement is very good for the $f_2(2300)$ tensor glueball candidate. At the same time, other tensor states -- such as $f_2(1270)$ and $f'_2(1520)$ -- have completely different distributions, which we interpret as consequence of the fact that they are not glueballs and thus, in our model, unrelated to the gravitational excitations, which are dual to spin-2 glueballs.

Glueballs and vector mesons at NICA

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 or in-medium broadening of vector and axial-vector mesons may occur there but the extent of such phenomena is still uncertain. Additionally, glueball properties could also be modified in medium. Exploration of these issues is the second suggested field of interest that can be pursued at NICA.

Light meson spectroscopy at BESIII

The BESIII collaboration has collected a sample of 1.311 billion J/ψ events since 2009. In this talk, we will introduce four recent analyses on light meson spec-troscopy at BESIII, including two studies on the X (1835) and two partial wave analyses that are related to searching for and studying glueball candidates.

Constraints on theηη′decay rate of a scalar glueball from gauge/gravity duality

Predictions of glueball decay rates in the holographic Witten-Sakai-Sugimoto model for low-energy QCD can be uniquely extended to include finite quark masses up to an as yet undetermined parameter in the coupling of glueballs to the nonanomalous part of the pseudoscalar mass terms. The assumption of a universal coupling of glueballs to mass terms of the full nonet of pseudoscalar mesons leads to flavor asymmetries in the decay rates of scalar glueballs that agree well with experimental data for the glueball candidate $f_0(1710)$ and implies a vanishing decay rate into $\eta\eta'$ pairs, for which only upper bounds for the $f_0(1710)$ meson are known at present from experiment. Relaxing this assumption, the holographic model gives a tight correlation between the decay rates into pairs of pseudo-Goldstone bosons of same type and $\eta\eta'$ pairs. If $\Gamma(G\to KK)/\Gamma(G\to\pi\pi)$ is kept within the range reported currently by the Particle Data Group for the $f_0(1710)$ meson, the rate $\Gamma(G\to\eta\eta')/\Gamma(G\to\pi\pi)$ is predicted to be $\lesssim 0.04$. The corresponding situation for $f_0(1500)$ is also discussed, which however is found to be much less compatible with the interpretation of a largely unmixed glueball.

Nonchiral Enhancement of Scalar Glueball Decay in the Witten-Sakai-Sugimoto Model.

We estimate the consequences of finite masses of pseudoscalar mesons on the decay rates of scalar glueballs in the Witten-Sakai-Sugimoto model, a top-down holographic model of low-energy QCD, by extrapolating from the calculable vertex of glueball fields and the η^{'} meson that follows from the Witten-Veneziano mechanism for giving mass to the latter. Evaluating the effect on the recently calculated decay rates of glueballs in the Witten-Sakai-Sugimoto model, we find a strong enhancement of the decay of scalar glueballs into kaons and η mesons, in fairly close agreement with experimental data on the glueball candidate f_{0}(1710).

Glueball decay rates in the Witten-Sakai-Sugimoto model

We revisit and extend previous calculations of glueball decay rates in the Sakai-Sugimoto model, a holographic top-down approach for QCD with chiral quarks based on D8 probe branes in Witten's holographic model of nonsupersymmetric Yang-Mills theory. The rates for decays into two pions, two vector mesons, four pions, and the strongly suppressed decay into four pi0 are worked out quantitatively, using a range of the 't Hooft coupling which closely reproduces the decay rate of rho and omega mesons and also leads to a gluon condensate consistent with QCD sum rule calculations. The lowest holographic glueball, which arises from a rather exotic polarization of gravitons in the supergravity background, turns out to have a significantly lower mass and larger width than the two widely discussed glueball candidates f0(1500) and f0(1710). The lowest nonexotic and predominantly dilatonic scalar mode, which has a mass of 1487 MeV in the Witten-Sakai-Sugimoto model, instead provides a narrow glueball state, and we conjecture that only this nonexotic mode should be identified with a scalar glueball component of f0(1500) or f0(1710). Moreover the decay pattern of the tensor glueball is determined, which is found to have a comparatively broad total width when its mass is adjusted to around or above 2 GeV.

On the analytic structure of scalar glueball operators at the Born level

We study the analytic structure of the two-point function of the operator ${F}^{2}$ which is expected to describe a scalar glueball. The calculation of the involved integrals is complicated by nonanalytic structures in the integrands, which we take into account properly by identifying cuts generated by angular integrals and deforming the contours for the radial integration accordingly. The obtained locations of the branch points agree with Cutkosky's cut rules. As input we use different nonperturbative Landau gauge gluon propagators with different analytic properties as obtained from lattice and functional calculations. All of them violate positivity and describe thus gluons absent from the asymptotic physical space. The resulting spectral densities for the glueball candidate show a cut but no poles for lightlike momenta, which can be attributed to the employed Born approximation.

Meson production in two-photon interactions at energies available at the CERN Large Hadron Collider

The meson production cross sections are estimated considering photon-photon interactions in hadron-hadron collisions at CERN Large Hadron Collider (LHC) energies. We consider a large number of mesons with photon-photon partial decay width well constrained by the experiment and some mesons which are currently considered as hadronic molecule and glueball candidates. Our results demonstrate that the experimental analysis of these states is feasible at the CERN LHC.

Low-lying scalars in an extended linearσmodel

We formulate an extended linear $\sigma$ model of a quarkonia nonet and a tetraquark nonet as well as a complex iso-singlet (glueball) by virtue of chiral symmetry $SU_L(3) \times SU_R(3)$ and $U_A(1)$ symmetry. In the linear realization formalism, we study the mass spectra and components of the low-lying scalars and pseudo scalars in this model. The mass matrices for physical staes are obtained and the glueball candidates are examined. We find that the model can accommodate the mass spectra of low-lying states quite well. Our fits indicate that the most glueball like scalar should be 2 GeV or higher while the glueball pseudoscalar is $\eta(1756)$. We also examine the parameter region where the lightest iso-scalar $f_0(600)$ can be the glueball and quarkonia dominant but find such a parameter region may be confronted with the problem of the unbounded vacuum from below.