Narrow Results

We study the mixing of excited states of a hydrogen atom in a cavity with de-excited states plus a confined photon as a model for the coupling of quark–antiquark and quark–antiquark–gluon hybrid states in QCD. For an interesting range of parameters, the results are analytic. We find a case for which wave functions (and hence decay patterns) may be at odds with mass with respect to identification of a state as hybrid or not.

Considering the strong coupling to a field of two particles bound by a quark–quark-like potential, we calculate the energy and width of a hybrid state in a simplified model.

A major component of the approved upgrade of the GSI facility in Darmstadt, Germany is the High Energy Storage Ring (HESR) for high intensity, phase space cooled antiprotons with momenta up to 15 GeV/c. At this facility a wide physics program is planned to investigate both the structure of hadrons in the charmonium mass range and the spectroscopy of double hypernuclei. To serve the many experiments planned at this new facility, a general purpose detector called PANDA (Proton ANtiproton Detector Array) is planned. An overview of the PANDA detector concept, as well as selected results from simulation of the detector's performance will be presented.

Recently GSI presented the plans for a major new international research facility, called FAIR. A key feature of this new facility will be the delivery of intense, high-quality secondary beams which embody the production of antiprotons. For the antiproton beams a High Energy Storage Ring (HESR) is comprised. The design luminosity is 2·10³²cm^-2s^-1. Experiments will take place at an internal target. The rich spectroscopy program on exotic hadrons with antiproton beams is presented.

Glueballs and hybrids are predicted to exist but searches for them have failed to provide conclusive evidence. One–gluon exchange is not an important part of strong interactions in this energy regime. Instead, quarks seem to interact indirectly, via changes of the QCD vacuum. Strong interactions seem to be governed by instanton–induced interactions; the chiral soliton model gives a more suitable interpretation of the Θ⁺(1540) than models based on the dynamics of four quarks and one antiquark.

This paper gives an introduction to the hadron physics program and the planned PANDA experiment at the future FAIR facility located at GSI in Germany.

Investigations of the mass and decays of the J^PC=1^-+ hybrid are reviewed, including calculation of the π₁(1^-+)→ηπ, η′π decay widths within the QCD sum rules technique. In this calculation, the recently-proposed η, η′ quark mixing scheme is employed. The results indicate that the decay width Γ_π1→ηπ≈250 MeV is large compared with the decay width Γ_{π1→η′π}≈20 MeV. Inspired by these results, some phenomenological approaches are suggested to gain an understanding of the underlying mechanism of ηπ and η′π hybrid decays.

A new resonance X(1835) in the J/psi radiative decays, a couple of significant enhancements near threshold, and clear evidences for a broad 1^-- resonant structure of K⁺K^-, the σ and κ mesons in the J/psi hadronic decays from BES are reported. Favored interpretations of these observations are discussed.

We examine resonances for two systems consisting of a particle coupled to a massless boson's field. The field is the free field in the whole space. In the first system, the particle is confined inside a ball. We show that besides the usual energy levels of the particle, which have become complex through the coupling to the field, other resonances are to be taken into account if the ball's radius is comparable to the particle's Compton wavelength. In the second system, the particle is in a finite-depth square-well potential. We study the way the resonances' energy and width depend on the extent of the uncoupled particle's wave functions. In both cases, we limit ourselves to considering two levels of the particle only.

We calculate resonances which are formed by a particle in a potential which is either Coulombian or quadratic when the particle is strongly coupled to a massless boson, taking only two energy levels into consideration. From these calculations we derive how the moving away of the particle from its attraction center goes together with the energy lowering of hybrid states that this particle forms with the field. We study the width of these states and we show that stable states may also appear in the coupling.

We present results from a Partial-Wave Analysis (PWA) of diffractive dissociation of 190 GeV/c π^- into π^-π⁺π^- final states on nuclear targets. A PWA of the data sample taken during a COMPASS pilot run in 2004 on a Pb target showed a significant spin-exotic J^PC = 1^-+ resonance consistent with the controversial π₁(1600), which is considered to be a candidate for a non- mesonic state. In 2008 COMPASS collected a large diffractive π^-π⁺π^- data sample using a hydrogen target. A first comparison with the 2004 data shows a strong target dependence of the production strength of states with spin projections M = 0 and 1.

The COMPASS experiment at CERN is well designed for light-hadron spectroscopy with emphasis on the detection of new states, in particular the search for J^PC-exotic states and glueballs. We have collected data with 190 GeV/c charged hadron beams on a liquid hydrogen and nuclear targets in 2008/09. The spectrometer features good coverage by electromagnetic calorimetry and a RICH detector further provides π K separation, allowing for studying final states involving neutral particles like π⁰ or η as well as hidden strangeness, respectively. We discuss the status of ongoing analyses with specific focus on diffractively produced (π⁰π⁰π)^- as well as final states.

A strategy for continuous fabrication of a microscale 3D-patterned hybrid composite film composed of alumina and acrylate resin was developed using roll-to-roll production. Conventional thermal curing was replaced with a UV curing procedure to facilitate rapid and economical processing. A seamless engraved soft urethane mold was first produced using a patterned metal roll. Subsequently, alumina and acrylate resin were cured on the engraved mold via UV irradiation to produce patterned hybrid films. The dispersion of alumina particles in acylate resin was enhanced by utilizing amine acrylate. Photopolymerization was measured using Fourier-transform infrared spectroscopy. The morphology of the soft engraved mold and the patterned hybrid film was investigated using scanning electron microscopy.

Palladium-catalyzed Suzuki–Miyaura coupling of 5-functionalized Ni(II) porphyrins with 1,3,6,8-tetrafunctionalizedpyrenes was carried out to obtain two kinds of porphyrin–pyrene hybrids. These compounds were comprehensively characterized by nuclear magnetic resonance (NMR), high-resolution mass spectrometry and ultraviolet-visible (UV-vis) absorption spectrometry, and their electrochemical properties were studied by both cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Fluorescence spectra for zinc compounds and free-base compounds were performed. In addition, the structure of 4Zn, a porphyrin tetramer, was determined by X-ray diffraction analysis, in which two planes formed by the porphyrin unit and the pyrene moiety adopt nearly perpendicular geometry with two sets of dihedral angles displaying 85.14 (4)${}^{°}$ and 83.90 (4)${}^{°}$, respectively. In the UV-vis absorption spectra, the maximum wavelengths of Soret bands and Q bands for these hybrids were observed at 434 and 648 nm. As the number of porphyrin units increases, the corresponding molar extinction coefficient rises markedly, in which the maximal value is 7.4 × 10⁵ M${}^{-1}$ • cm${}^{-1}$ belonging to 4Zn. Moreover, the presence of energy transformation from the pyrene moiety to the porphyrin unit has been proved by emission spectra. Finally, the electrochemical properties of these porphyrin–pyrene hybrids were analyzed by using cyclic voltammetry and differential pulse voltammetry, which show that the nickel hybrids possessed the maximal electrochemical highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) gap and the zinc compounds displayed the minimum electrochemical HOMO–LUMO gap.

Carbon nanotube-inorganic hybrid materials have stimulated a new boost in CNT research as a new class of multifunctional materials with properties distinct from the well-known CNT composites. Synergistic effects based on interfacial charge and heat transfer processes commend these hybrids for use in photocatalysis, gas sensors and in electrochemical devices. A major challenge is the synthesis of hybrids with hierarchical architectures and controlled interfaces. Common wet-chemical techniques have the major drawback that the CNT array typically collapses upon drying due to stresses imposed by the surface tension of the solvent. In this work, we synthesized hierarchical hybrids with coherent 3D architectures using unique CNT fibers, based on the "Cambridge process" as well as vertical arrays of CNTs ("carpets"). We demonstrate that separating the liquid reactants from the CNT array is key to preserving the hybrid's architecture. In addition, we show that the presence of benzyl alcohol as a linking agent is beneficial to maximizing the interfacial area in TiO₂-coated CNT fibers.

Multi-component hybrid materials are intriguing. They have the potential to act as a platform to manifest the properties of their components. In this review, we discuss the catalytic applications of few such hybrids that are based on oxometalates (OMs). Due to the structural flexibility and enormous properties, OMs are unrivaled in the field of catalysis. Thus, here we primarily focus on the synthesis and catalysis of such OM-based hybrids. The present overview shows that it is possible to improve the catalytic property of bare oxometalates and even that of their soft-matter state namely soft-oxometalates (SOMs) through rational choice of organic ligand and oxometalates.

The QCD analysis of the recent experimental data (L3@LEP) of the hard exclusive ρρ production in two photon collisions shows that these data can be understood as a signal for the existence of an exotic isotensor resonance with a mass around 1.5 GeV. We also argue that hard exclusive reactions are a powerful tool for an experimental study of exotic hybrid mesons with J^PC = 1^-+.

Many charmonium-like and bottomonium-like XYZ resonances have been observed by the Belle, Babar, CLEO and BESIII collaborations in the past decade. They are difficult to fit in the conventional quark model and thus are considered as candidates of exotic hadrons, such as multi-quark states, meson molecules, and hybrids. In this talk, we first briefly introduce the method of QCD sum rules and then provide a short review of the mass spectra of the quarkonium-like tetraquark states and the heavy quarkonium hybrids in the QCD sum rules approach. Possible interpretations of the XYZ resonances are briefly discussed.