Narrow Results

In the framework of meson–meson mixing, in the presence of the a₄(2040), and f₄(2050) being the 1 ³F₄ states, we suggest that the f′₄, the ninth member of the 1 ³F₄ meson nonet, has a mass of about 2084 MeV, and some predictions on the f₄ and f′₄ decaying into two photons and pseudoscalar mesons are presented. Also, the mass of the lowest lying 4⁺⁺ glueball is predicted to be about 3.15 GeV by using the meson-glueball mass relation derived from the glueball dominance picture, which is in agreement with 3.42 GeV, the average value of the recent predicted results was given by lattice QCD, potential model, semi-relativistic potential model and quasi-particle model.

We calculate the glueball 〈gg〉 wavefunction and mass in SU(3) Lattice gauge with improved gauge actions on the anisotropic lattice. All simulations are performed on the cluster of our lab. We have measured the scalar and tensor glueball wavefunction. At the same time, we have briefly calculated the glueball mass as for a consistent check.

Data of the Crystal Barrel and L3 collaborations clarified essentially the situation in the 2⁺⁺ sector in the mass region up to 2400 MeV, demonstrating the linearity of (n, M²) trajectories, where n is the radial quantum number of a quark–antiquark state with mass M. We discuss these data and show that there exists a superfluous state for the (n, M²) trajectories: a broad resonance f₂(2000). We pay special attention to the reactions in the mass region 1990–2400 MeV where, together with f₂(2000), four relatively narrow resonances are seen: f₂(1920), f₂(2020), f₂(2240), f₂(2300). We analyze the branching ratios of all these resonances and show that only the decay couplings of the broad state f₂(2000) → π⁰π⁰, ηη, ηη′ satisfy relations inherent in the glueball decay.

We present a short review of the current understanding of the scalar meson sector, with special attention to the problem of the low-mass σ. The dispersion relation N/D-method used for the restoration of the low-energy ππ (IJ^PC = 00⁺⁺)-wave amplitude is discussed. The low-energy ππ amplitude was determined from the data in the energy region 280–500 MeV and it was sewn with the previously found K-matrix solution for the region 450–1950 MeV. The N/D-amplitude has a pole on the second sheet of the complex-s plane, near the ππ threshold at , that corresponds to the low-mass σ-meson. We discuss the hypothesis that this pole may be related to the confinement forces, thus being the eyewitness of confinement.

We discuss the scalar meson mixing scenario and present an OZI rule violation mechanism for understanding the scalar productions in charmoium hadronic decays. We stress that the OZI violation could play a key role in disentangling the structure of the scalars: f₀(1370), f₀(1500) and f₀(1710).

We investigate 3D Yang-Mills theory coupled to an adjoint scalar, which can be regarded as a zeroth order approximation in (de)constructing 4D Yang-Mills theory. We develop a new algorithm to obtain the renormalized Hamiltonian with the Karabali-Nair variable, by carefully identifying finite local counterterms. We also discuss how this formalism can be applied to obtain glueball spectrum.

We report here on recent advances that shed light on the topic of scalar meson sector, which is controversial up to date. We study the scattering and spectroscopy of the strongly interacting mesons in coupled channels with quantum numbers J^PC = 0⁺⁺ and I = 0 and I = 1/2, up to a center of mass energy . Our framework is based on Unitary Chiral Perturbation Theory, but extended now to include many more channels. The resonant content of our fits is discussed, with the appearence of σ, f₀(980), f₀(1310), f₀(1500), f₀(1710) and f₀(1790) for I = 0 and the κ and the for I = 1/2.

I give a brief introduction to central exclusive production in hadron–hadron collisions, the subject of this special issue of the International Journal of Modern Physics A.

The CERN Intersecting Storage Rings, with from 22 GeV to 63 GeV and , allowed the first observations of p + p → p + X + p with two leading protons (x_F > 0.95) or two rapidity gaps Δy > 3. Studies of the central hadronic system (X) were made to search for glueballs, finding f₀ and f₂ resonances, and to advance our understanding of hadronic diffraction. I review the experiments, not including those at the Split Field Magnet (SFM) facility covered elsewhere in this volume. Some double pomeron exchange studies at the CERN Collider are also covered.

At CERNs Large Hadron Collider, a unique possibility to study central exclusive processes such as the production of low mass resonances, charmonium states and jets, as well as to search for missing mass or momentum signatures opens up by the detection of both leading protons with the special β* = 90 m optics. At with that optics the leading proton acceptance of the TOTEM Roman Pots covers all diffractive masses, provided that the proton four-momentum transfer |t| ≳ 0.04 GeV². This paper describes the physics potential with an integrated luminosity of 10 pb^-1 and 100 pb^-1 for common CMS and TOTEM data taking at β* = 90 m optics.

We derive the bound state equation for two gluons in relativistic quantum field theory, i.e. the Bethe–Salpeter (BS) equation for two gluons. To solve it, we choose the kernel as the sum of a one-gluon exchange potential, a contact interaction and a linear confining potential. Under instantaneous approximation, this BS equation is solved numerically. The spectrum and the BS wave function of the glueballs are obtained in this framework. The numerical results are in agreement with that of recent lattice calculation.

We investigate the two-meson decay modes for f₀(1710). In this calculation, we consider this resonance as a glueball. The Fock–Tani formalism is introduced to calculate the decay width.

In this work we use a mapping technique to derive in the context of a constituent gluon model an effective Hamiltonian that involves explicit gluon degrees of freedom. We study glueballs with two gluons using the Fock-Tani formalism. In the present work we calculate the glueball-glueball potential, in the context of the constituent gluon model, with gluon interchange.

In the last years many exotic states have been identified in several colliders around the world. One of the exotic states provided in QCD is the glueball. Using a non-relativistic gluon bound-state model, we compute $\mathrm{\Gamma }(G\to \gamma \gamma )$, where $G$ is a pseudoscalar, tensor, or scalar digluon. For the starting from the amplitudes we considers the process $\gamma \gamma \to g^{\ast }{g}^{\ast }$ at threshold, where the amplitudes are obtained in perturbative QCD at lowest order by deriving them from QED calculation and the $g^{\ast }$s are massive constituent gluons. In this calculation the unknown parameters of the model, such as the digluon wave function, are obtained using measured values of $\mathrm{\Gamma }(J/\mathrm{\Psi }\to G\gamma )$. Our theorical results are compared with the present experimental limits for the various glueballs candidates.

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 $X(1835)$ resonance. In our calculation the $X(1835)$ was a pure glueball.

BESIII has collected $1.3\times 10^{8}J/\psi$ and $0.4\times 10^8$ of ${\psi }^{\prime }$, which are the world’s largest data samples of $J/\psi$ and ${\psi }^{\prime }$ from $e^{+}{e}^{-}$ collision. Radiative decays of charmonium provide a gluon-rich environment and are therefore regarded as one of the most promising hunting grounds for gluonic excitations. Significant progresses in the light-quark sector have been made with the unprecedented high statistics data sets. Several recent results on light hadron spectroscopy and light hadron decays will be reported, including: 1, the observation of the anomalous line shape of $X(1835)$ near $p\bar{p}$ mass threshold and related studies; 2, studies of glueballs in $J/\psi$ radiative decays; 3, search for $1^{-+}$ exotic in ${\chi }_{c1}\to \eta \pi \pi$.

The study of light hadrons is central to the understanding of confinement–a unique property of QCD. The quark model describs mesons as bound states of quarks and antiquarks. LQCD and QCD-motivated models for hadrons, however, predict a richer spectrum of mesons that takes into account not only the quark degrees of freedom but also the gluonic degrees of freedom. A selection of recent progress in the light-quark sector with unprecedented high-statistics data sets from e⁺e⁻ experiments are reviewed.

It is shown that the conventional mesons and the lowest glueball state can be reasonably described within a simple relativistic quantum-field model of interacting quarks and gluons under the analytic confinement by using a path-integral approach. The ladder Bethe-Salpeter equation is solved for the meson and glueball (gg) spectra. A minimal set of parameters (the quark masses m_f, the coupling constant α_s and the confinement scale Λ) is used to fit the latest experimental data. In spite of the simplicity, the model provides a reasonable framework to estimate the decay constants f_π and f_K as well as the non-exotic meson and glueball masses in a wide range of energy up to 10 GeV.

On October 4th, 2010, nine countries signed the international agreement on the construction of the Facility for Antiproton and Ion Research FAIR. The new facility is going to be constructed within the next eight years adjacent to the existing accelerator complex of the GSI Helmholtz Centre for Heavy Ion Research at Darmstadt/Germany, expanding the research goals and technical possibilities substantially. Providing a broad spectrum of unprecedented fore-front research at worldwide unique accelerator and experimental facilities, FAIR will open the way for a large variety of experiments in hadron, nuclear, atomic and plasma physics as well as applied sciences which will be briefly described in this article.

Questions to discuss:

• Is heavy quark flavor physics really needed in the LHC era? If LHC discovers new physics, how will flavor physics help to interpret it? What if LHC finds nothing new?
• There is a flow of experimental results on XYZ states and their interpretations. Is there a convergence or a consensus on any of these?
• Most of experiments deal with s-channel formation of baryons. Are other mechanisms like t-channel useful as a complementary source?
• Is there a feasible unification of data presentation from various experiments for mesons similar to what is done for baryon spectroscopy?
• Where are glueballs?