Related papers: Studies of $\eta^{(')}\pi$ Final States Using Glue…
The excitation spectrum of light mesons, which are composed of up, down, and strange quarks, is studied since decades. However, it still holds a number of puzzles and surprises that provide new insights into the nature of the strong…
Excited vector mesons, some of which are predicted to include gluonic excitation in their wavefunctions, and certain classes of axial vector mesons, some of which are implicated in the decay of spin-exotic mesons, decay dominantly to…
The recent search for non $q \bar{q}$ mesons in $\pi^{-}p$ interactions at Brookhaven National Laboratory is summarized. Many final states such as $\eta \pi$, $\eta' \pi^{-}$, $a_{0} \pi$, $f_{1} \pi$, $a_{2} \pi$, $b_{1} \pi$, which are…
In this paper, I review the experimental situation for both glueballs and hybrid mesons. Theoretical expectations are discussed, and a survey of what is known about hybrid mesons and glueballs is undertaken. Good experimental evidence…
Quantum Chromodynamics (QCD) is the theory that describes how hadrons are built from quarks and gluons via the strong interaction. Many predictions have been experimentally confirmed, but others remain under experimental investigation. Of…
One of the prime goals of the COMPASS experiment at CERN is the study of the light meson spectrum, with a particular emphasis on the search for exotic states. We present the first high-statistics partial-wave decomposition of the…
The goal of the COMPASS experiment at CERN is to study the structure and spectroscopy of hadrons. The two-stage spectrometer has large acceptance and covers a wide kinematic range for charged as well as neutral particles allowing to access…
Decays of the neutral and long-lived $\eta$ and $\eta'$ mesons provide a unique, flavor-conserving laboratory to test low-energy Quantum Chromodynamics and search for new physics beyond the Standard Model. They have drawn world-wide…
We investigate the possibility that the light-mass exotic mesons with J^PC=1^-+ observed at BNL and CERN may be resonances in the eta-pi and eta'-pi systems associated with the anomalous glue which generates the eta' mass in QCD.
We provide an overview of theoretical developments on hybrid mesons and glueballs in the last year at this turn of the millenium conference. Cracks in potential models of conventional mesons are developing. Hybrid meson adiabatic surfaces…
The GlueX experiment at Jefferson Lab has been designed to study photoproduction reactions with a 9-GeV linearly polarized photon beam. The energy and arrival time of beam photons are tagged using a scintillator hodoscope and a…
We describe an experiment to search for a new vector boson A' with weak coupling alpha' > 6 x 10^{-8} alpha to electrons (alpha=e^2/4pi) in the mass range 65 MeV < m_A' < 550 MeV. New vector bosons with such small couplings arise naturally…
The experimental information on the search for non $q \bar q$ mesons as glueballs, hybrids and multiquark states is reviewed. Candidate states which are particularly amenable to detailed study by accumulating large samples of $J/\psi$,…
Two mechanisms for the $\pi_1$ ($J^{PC}=1^{-+}$) hybrid meson decay processes $\pi_1\to\eta\pi,\eta'\pi$ are investigated. These mechanisms are applied to $\phi\to\eta\gamma,\eta'\gamma$ and $J/\psi\to\eta\gamma,\eta'\gamma$ decays to…
The $\pi_1(1600)$, a $J^{PC} = 1^{-+}$ exotic meson has been observed by experiments using pion beams. Theorists predict that photon beams could produce gluonic hybrid mesons, of which the $\pi_1(1600)$ is a candidate, at enhanced levels…
A model of light hybrid mesons and their strong decays is developed. The model employs a gluonic quasiparticle to describe low energy gluodynamics and uses the QCD Hamiltonian in Coulomb gauge to guide the construction of states and decay…
The spin-exotic hybrid meson $\pi_{1}(1600)$ is predicted to have a large decay rate to the $\omega\pi\pi$ final state. Using 76.6~pb$^{-1}$ of data collected with the GlueX detector, we measure the cross sections for the reactions $\gamma…
The status of non-perturbative QCD calculations for mesons with gluonic excitation is presented. Lattice results for the glueball spectrum are reviewed. For hybrid mesons, the heavy quark results are summarised and new results are presented…
The processes $e^+e^-\to e^+e^-X$, with $X$ being either the $\eta$ meson or $\pi^0\pi^0$, are studied at DA$\Phi$NE, with $e^+e^-$ beams colliding at $\sqrt{s}\simeq1$ GeV, below the $\phi$ resonance peak. The data sample is from an…
Using the recently proposed $gg --> eta'$ effective vertex, we investigate the production of $\eta'$ from gluon fusion in $pA$ collisions. We show that measuring $\eta'$ production cross-section at moderate $x_{\eta'}$ yields direct…