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The spectrum of excited hadrons - mesons and baryons - serves as an excellent probe of quantum chromodynamics (QCD), the fundamental theory of the strong interaction. The strong coupling however makes QCD challenging. It confines quarks and breaks chiral symmetry, thus providing us with the world of light hadrons. Highly-excited hadronic states are sensitive to the details of quark confinement, which is only poorly understood within QCD. This is the regime of nonperturbative QCD and it is one of the key issues in hadronic physics to identify the corresponding internal degrees of freedom and how they relate to strong coupling QCD. The quark model suggests mesons are made of a constituent quark and an antiquark and baryons consist of three such quarks. QCD predicts other forms of matter. What is the role of glue? Resonances with large gluonic components are predicted as bound states by QCD. The lightest hybrid mesons with exotic quantum numbers are estimated to have masses in the range from 1 to 2 GeV/c2 and are well in reach of current experimental programs. At Jefferson Laboratory (JLab) and other facilities worldwide, the high-energy electron and photon beams present a remarkably clean probe of hadronic matter, providing an excellent microscope for examining atomic nuclei and the strong nuclear force. [ABSTRACT FROM AUTHOR]

The spectrum of excited hadrons - mesons and baryons - serves as an excellent probe of quantum chromodynamics (QCD), the fundamental theory of the strong interaction. The strong coupling however makes QCD challenging. It confines quarks and breaks chiral symmetry, thus providing us with the world of light hadrons. Highly-excited hadronic states are sensitive to the details of quark confinement, which is only poorly understood within QCD. This is the regime of nonperturbative QCD and it is one of the key issues in hadronic physics to identify the corresponding internal degrees of freedom and how they relate to strong coupling QCD. The quark model suggests mesons are made of a constituent quark and an antiquark and baryons consist of three such quarks. QCD predicts other forms of matter. What is the role of glue? Resonances with large gluonic components are predicted as bound states by QCD. The lightest hybrid mesons with exotic quantum numbers are estimated to have masses in the range from 1 to 2 GeV/c² and are well in reach of current experimental programs. At Jefferson Laboratory (JLab) and other facilities worldwide, the high-energy electron and photon beams present a remarkably clean probe of hadronic matter, providing an excellent microscope for examining atomic nuclei and the strong nuclear force. [ABSTRACT FROM AUTHOR]

We report on hadron spectroscopy using the CLAS at Jefferson Lab. We present preliminary results from photoproduction experiments studying the spectroscopy of exotic mesons, cascades (Ξ's) and Dalitz decays of pseudo-scalar mesons in the largest data sample ever to be produced at photon energies of about 5 GeV. We also describe, briefly, a new experiment to continue hadron spectroscopy at CLAS12 (at Jefferson Lab energy upgrade) using electroproduction at very low Q2 ("quasireal photons") up to photon energies of 10 GeV. [ABSTRACT FROM AUTHOR]

A Dyson-Schwinger equation calculation of the light hadron spectrum, which correlates the masses of meson and baryon ground- and excited-states within a single framework, produces a description of the Roper resonance that corresponds closely with conclusions drawn recently by EBAC. Namely, the Roper is a particular type of radial excitation of the nucleon's dressed-quark core augmented by a material meson cloud component. There are, in addition, some surprises. [ABSTRACT FROM AUTHOR]

The latest results on B hadron spectroscopy from the DO\ experiment at the Tevatron are presented. The mass measuremen of the Bc- meson in the Bc-→J/ψπ- decay channel, the observation of excited Bs mesons, the first direct observation of the Ξb- baryon, and the first observation of the Ωb- baryon. [ABSTRACT FROM AUTHOR]

Recent studies concerning charmed baryon spectroscopy, performed by the Belle collaboration, are briefly described. We report the first observation of two new baryons [cap_xi]cx(2980) and [cap_xi]cx(3077), a precise determination of the masses of [cap_xi]c(2645) and [cap_xi]c(2815), observation of the Λc(2940)+ and experimental constraints on the possible spin-parity of the Λc(2880)+. Observations of several exclusive decays of B mesons to the final states containing charmed baryons are also briefly presented. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

The studies on the light scalar mesons and excited baryon states at BES are presented, based on 5.8 × 107 J / ψ data collected with BESII detector. The measurements of some J / ψ and ηc decays are also presented in this report. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Progress in computing the spectrum of excited baryons and mesons in lattice QCD is described. Large sets of spatially-extended hadron operators are used. The need for multi-hadron operators in addition to single-hadron operators is emphasized, necessitating the use of a new stochastic treatment of the low-lying modes of quark propagation which exploits Laplacian Heaviside quark-field smearing. A new glueball operator is tested and computing the mixing of this glueball operator with a quark-antiquark operator and multiple two-pion operators is shown to be feasible. [ABSTRACT FROM AUTHOR]