Pseudoscalar Glueball Research Articles

Pseudoscalar glueball in a chiral Lagrangian model with instanton effect

We study the pseudoscalar glueball ground state in a chiral effective Lagrangian model proposed by 't Hooft, motivated by taking into account the instanton effects, which can describe not only the chiral symmetry breaking, but also the solution of ${U}_{A}(1)$. We study the parameter space allowed by constraints from vacuum conditions and unitary bounds. By considering two scenarios in the ${0}^{++}$ sector, we find that parameter space which can accommodate the ${0}^{\ensuremath{-}+}$ sector is sensitive to the conditions in ${0}^{++}$ sector. From our analysis, it is found that three $\ensuremath{\eta}$ states, i.e. $\ensuremath{\eta}(1295)$, $\ensuremath{\eta}(1405)$, $\ensuremath{\eta}(1475)$, can be the pseudoscalar glueball ground state if we assume that the lightest ${0}^{++}$ glueball ground state has a mass 1710 (or 1500) MeV. While there will be no ${0}^{\ensuremath{-}+}$ glueball candidate ground state found in experiments if we assume that the lightest ${0}^{++}$ glueball ground state has a mass 660 MeV. We also point out the determined instanton density (i.e. the parameter ${k}_{t}$) is consistent with those determined from other methods, e.g. instanton liquid approximation and lattice simulations.

SCALAR AND PSEUDOSCALAR GLUEBALLS

We employ two simple and robust results to constrain the mixing matrix of the isosinglet scalar mesons f0(1710), f0(1500), f0(1370): one is the approximate SU (3) symmetry empirically observed in the scalar sector above 1 GeV and confirmed by lattice QCD, and the other is the scalar glueball mass at 1710 MeV in the quenched approximation. In the SU (3) symmetry limit, f0(1500) becomes a pure SU (3) octet and is degenerate with a0(1450), while f0(1370) is mainly an SU (3) singlet with a slight mixing with the scalar glueball which is the primary component of f0(1710). These features remain essentially unchanged even when SU (3) breaking is taken into account. The observed enhancement of ωf0(1710) production over ɸf0(1710) in hadronic J/ψ decays and the copious f0(1710) production in radiative J/ψ decays lend further support to the prominent glueball nature of f0(1710). We deduce the mass of the pseudoscalar glueball G from an η-η′-G mixing formalism based on the anomalous Ward identity for transition matrix elements. With the inputs from the recent KLOE experiment, we find a solution for the pseudoscalar glueball mass around (1.4±0.1) GeV, which is fairly insensitive to a range of inputs with or without Okubo-Zweig-Iizuka-rule violating effects. This affirms that η(1405), having a large production rate in the radiative J/ψ decay and not seen in γγ reactions, is indeed a leading candidate for the pseudoscalar glueball. It is much lower than the results from quenched lattice QCD (> 2.0 GeV) due to the dynamic fermion effect. It is thus urgent to have a full QCD lattice calculation of pseudoscalar glueball masses.

η(1405)in a chiral approach based on mixing of the pseudoscalar glueball with the first radial excitations ofηandη′

The supernumerous $\ensuremath{\eta}(1405)$ is considered a strong candidate for the pseudoscalar glueball. In a phenomenological chiral approach, we consider a mixing scenario of bare pseudoscalar $n\overline{n}$ and $s\overline{s}$ quarkonia with the glueball. We study the decay properties and point out the peculiarities of this scenario in order to support the possible identification of the ${J}^{\mathrm{PC}}={0}^{\ensuremath{-}+}$ glueball.

Pseudoscalar glueball mass fromη-η′-Gmixing

We deduce the mass of the pseudoscalar glueball G from an {eta}-{eta}{sup '}-G mixing formalism based on the anomalous Ward identity for transition matrix elements. With the inputs from the recent KLOE experiment, we find a solution for the pseudoscalar glueball mass around (1.4{+-}0.1) GeV, which is fairly insensitive to a range of inputs with or without Okubo-Zweig-Iizuka-rule violating effects. This affirms that {eta}(1405), having a large production rate in the radiative J/{psi} decay and not seen in {gamma}{gamma} reactions, is indeed a leading candidate for the pseudoscalar glueball. Other relevant quantities including the anomaly and pseudoscalar density matrix elements are obtained. The decay widths for G{yields}{gamma}{gamma}, l{sup +}l{sup -} are also predicted.

On normal modes of a warped throat

As shown in arXiv:hep-th/0405282, the warped deformed conifold has two bosonic massless modes, a pseudoscalar and a scalar, that are dual to the phase and the modulus of the baryonic condensates in the cascading gauge theory. We reconsider the scalar mode sector, mixing fluctuations of the NS-NS 2-form and the metric, and include non-zero 4-d momentum $k_\mu$. The resulting pair of coupled equations produce a discrete spectrum of $m_4^2=- k_\mu^2$ which is interpreted as the spectrum of $J^{PC}= 0^{+-}$ glueballs in the gauge theory. Similarly, we derive the spectrum of certain pseudoscalar glueballs with $J^{PC}= 0^{--}$, which originate from the decoupled fluctuations of the RR 2-form. We argue that each of the massive scalar or pseudoscalar modes we find belongs to a 4-d massive axial vector or vector supermultiplet. We also discuss our results in the context of a finite length throat embedded into a type IIB flux compactification.

Euclidean correlation functions in a holographic model of QCD

We compute Euclidean coordinate space correlation functions in a holographic model of QCD. We concentrate, in particular, on channels that are related to the $U(1{)}_{A}$ problem, the flavor-singlet axial vector, pseudoscalar meson, and pseudoscalar glueball (topological charge) correlator. We find that even a very simple holographic model defined on a slice of five-dimensional anti-de Sitter space provides a qualitatively correct description of QCD correlation functions. We study the role of anomaly terms, and show that both Euclidean positivity and low energy theorems based on the axial anomaly relation are correctly implemented. We compare the results with expectations from an instanton model of the QCD vacuum.

Decays of J/ψ and ψ′ into vector and pseudoscalar mesons and the pseudoscalar glueball– mixing

We introduce a parametrization scheme for J/ψ(ψ′) → VP where the effects of SU(3) flavor symmetry breaking and doubly OZI-rule violation (DOZI) can be parametrized by certain parameters with explicit physical interpretations. This scheme can be used to clarify the glueball– mixing within the pseudoscalar mesons. We also include the contributions from the electromagnetic (EM) decays of J/ψ and ψ′ via J/ψ(ψ′) → γ* → VP. Via study of the isospin violated channels, such as J/ψ(ψ′) → ρη, ρη′, ωπ0 and ϕπ0, reasonable constraints on the EM decay contributions are obtained. With up-to-date experimental data for J/ψ(ψ′) → VP, J/ψ(ψ′) → γP and P → γγ, etc, we arrive at a consistent description of the mentioned processes with a minimal set of parameters. As a consequence, we find that there exists an overall suppression of the ψ′ → 3g form factors, which sheds some light on the long-standing ‘ρπ puzzle’. By determining the glueball components inside the pseudoscalar η and η′ in three different glueball– mixing schemes, we deduce that the lowest pseudoscalar glueball, if it exists, has a rather small component, and it makes η(1405) a preferable candidate for a 0−+ glueball.

Glueball-induced partonic energy loss in quark-gluon plasma

We discuss the energy loss of energetic parton jets in quark-gluon plasma above the deconfinement temperature T{sub c} by the interaction with scalar and pseudoscalar glueballs. It is shown that the loss by this mechanism is quite important and may play the important role of the observed jet quenching.

Role of glueballs in non-perturbative quark–gluon plasma

Discussed is how non-perturbative properties of quark gluon plasma, recently discovered in RHIC experiment, can be related to the change of properties of scalar and pseudoscalar glueballs. We set up a model with the Cornwall–Soni's glueball–gluon interaction, which shows that the pseudoscalar glueball becomes massless above the critical temperature of deconfinement phase transition. This change of properties gives rise to the change of sign of the gluon condensate at T>Tc. We discuss the other physical consequences resulting from the drastic change of the pseudoscalar glueball mass above the critical temperature.

Formula omitted] as the lowest mass pseudoscalar glueball and proton spin problem

We consider the parity doublet structure observed in high hadronic excitations within the instanton model for the QCD vacuum. In the conventional approach this doubling phenomenon is treated as a manifestation of the partial restoration of chiral or U(1)A symmetry. We demonstrate that the suppression of direct instanton contribution to the masses of excited hadrons leads to the partial U(1)A symmetry restoration in hadron spectrum. The origin of X(1835) resonance observed by BES Collaboration is studied upon the doublet structure. We argue also how X(1835) be interpreted as the lowest pseudoscalar glueball state, and derive its coupling constant to proton. It turns out that this coupling is large and negative. Demonstrated is how this large coupling affects the gluonic contribution to the proton spin.

ηc-glueball mixing and resonance X(1835)

The mixing of ${\ensuremath{\eta}}_{c}$ and the lowest mass pseudoscalar glueball is estimated within the framework of the instanton liquid model. It is demonstrated that the mixing is large and may explain the difference between the observed mass of the glueball candidate X(1835) and the theoretical prediction of the QCD sum rule analysis.

On theta dependence of glueballs from AdS/CFT

We study the theta dependence of the glueball spectrum in a strongly coupled cousin of large N gluodynamics defined via the AdS/CFT correspondence. By explicitly diagonalizing the 10d gravity equations in the presence of the RR 3-form and 1-form fluxes we found a mixing pattern for the lowest-spin lightest glueballs. The mixing between the scalar and pseudoscalar states is not suppressed, suggesting that the CP-odd effects persist in the large N theory. As a consequence, the lightest mass eigenstate ceases to be a parity eigenstate. We found the former as a linear combination of a scalar and pseudoscalar glueballs. On the other hand, the mass eigenvalues in a theory with and without the theta term remain equal in the large N limit.

The holographic life of the η′

In the string holographic dual of large-Nc QCD with Nf ∞avours of (1), the · 0 meson is massless at inflnite Nc and dual to a collective ∞uctuation of Nf D6-brane probes in a supergravity background. Here we identify the string diagrams responsible for the gen- eration of a mass of order Nf=Nc, consistent with the Witten-Veneziano formula, and show that the supergravity limit of these diagrams corresponds to mixings with pseudoscalar glueballs. We argue that the dependence on the µ-angle in the supergravity description occurs only through the combination µ + 2 p Nf· 0 =f…, as dictated by the U(1)A anomaly. We provide a quantitative test by computing the linear term in the · 0 potential in two independent ways, with perfect agreement.

Glueballs, symmetry breaking and axionic strings in non-supersymmetric deformations of the Klebanov-Strassler background

We obtain an analytic solution for an axionic non-supersymmetric deformation of the warped deformed conifold. This allows us to study D-strings in the infrared limit of non-supersymmetric deformations of the Klebanov-Strassler background. They are interpreted as axionic strings in the dual field theory. Following the arguments of [hep-th/0405282], the axion is a massless pseudo-scalar glueball which is present in the supergravity fluctuation spectrum and it is interpreted as the Goldstone boson of the spontaneously broken U(1) baryon number symmetry, being the gauge theory on the baryonic branch. Besides, we briefly discuss about the Pando Zayas-Tseytlin solution where the SU(2) \times SU(2) global symmetry is spontaneously broken. This background has been conjectured to be on the mesonic branch of the gauge theory.

Symmetry Breaking and Axionic Strings in the Warped Deformed Conifold

We interpret D-strings at the bottom of the warped deformed conifold as axionic strings in the dual cascading SU(N+M) x SU(N) gauge theory. The axion is a massless pseudo-scalar glueball which we find in the supergravity fluctuation spectrum and interpret as the Goldstone boson of spontaneously broken U(1) baryon number symmetry. The existence of this massless glueball, anticipated in hep-th/0101013, supports the idea that the cascading gauge theory is on the baryonic branch, i.e. the U(1)_B global symmetry is broken by expectation values of baryonic operators. We also find a massless scalar glueball, which is a superpartner of the pseudo-scalar. This scalar mode is a mixture of an NS-NS 2-form and a metric perturbation of the warped deformed conifold of a type first considered in hep-th/0012034.

Topological charge screening and pseudoscalar glueballs

Topological charge screening in the QCD vacuum is found to provide crucial nonperturbative contributions to the short-distance expansion of the pseudoscalar (0^{-+}) glueball correlator. The screening contributions enter the Wilson coefficients and are an indispensable complement to the direct instanton contributions. They restore consistency with the anomalous axial Ward identity and remedy several flaws in the 0^{-+} glueball sum rules caused by direct instantons in the absence of screening (lack of resonance signals, violation of the positivity bound and of the underlying low-energy theorem). The impact of realistic instanton size distributions and the (gauge-invariant) renormalization of the instanton contributions are also discussed. Predictions for the 0^{-+} glueball mass and decay constant are presented.

Semiclassical double-Pomeron production of glueballs andη′

A semiclassical theory of high energy scattering based on interrupted tunneling (instantons) or QCD sphaleron production has been recently developed to describe the growing hadronic cross section and properties of the soft Pomeron. In this work we address double-pomeron processes in this framework for the first time. We specifically derive the cross section for central production of parity even and odd clusters, scalar and pseudoscalar glueballs, and $\eta'$ in parton-parton scattering at high energy. We show that the specific dependence of the production cross section on all its kinematical variables compares favorably with the UA8 data on inclusive cluster production, as well as the WA102 data on exclusive central production of scalar glueball and $\eta'$, in double-pomeron exchange $pp$ scattering. The magnitude of the cross section and its dependece on kinematic variables is correct, explaining in particular a large deviation from the Pomeron factorization at cluster masses in the range $M_X<8$ GeV reported by UA8.

GLUON CORRELATORS IN THE KOGAN–KOVNER MODEL

The Lorentz-invariant gluon correlation functions &lt;F2(x) F2(x′)&gt; and [Formula: see text], corresponding to scalar and pseudoscalar glueballs, are calculated for Kogan's and Kovner's variational ansatz for the pure SU (N) Yang–Mills wave functional. One expects only one dynamical mass scale should be present in QCD; the ansatz generates the expected scale for both glueballs, as well as an additional scale for the scalar glueball coming from the correlator of the color electric field. The additional mass scale must therefore vanish, or be close to the expected one. This is shown to constrain the nature of the phase transition in the Kogan–Kovner ansatz.

THE MASS RELATION BETWEEN THE PURE AND PHYSICAL GROUND PSEUDOSCALAR GLUEBALLS

The experimental information indicates that for the ground pseudoscalar states, the omission of the transition amplitudes between quarkonia can result in the unreasonable result. It is believed that the mass of the pure glueball employed in the general form of the mass matrix is different from the mass predicted by lattice QCD in quenched approximation for the ground pseudoscalar glueball. The mass relation between the pure and physical ground pseudoscalar glueballs is determined from the experimental data.

New meson mass relation and lowest pseudoscalar glueball mass

A new meson mass relation for meson nonet is given after considering mixing with glueball. The mixing between pseudoscalar mesons and pseudoscalar glueball will decrease the mass of glueball by about 500 Mev. So, according to the predicted mass of the pure pseudoscalar glueball given by lattice calculation and effective Hamiltonian, the expected mass of mixed pseudoscalar glueball is about 1.7 Gev. This result is helpful for experimemtal search for the mixed Isoscalar pseudoscalar glueball.