[en] The E(G) (1420) may be an s antis state, a glueball, or both. We study the spectrum of s antis and transverse gg states in potential models to see if the alternatives can easily be distinguished. We conclude that either identification is possible; the models require Msub(s antis)(1⁺⁺) = 1.45 GeV and Msub(gg) (0^-+) approximately 1.3 GeV. The glueball option predicts a degenerate 0⁺⁺ gg state. We also discuss the masses and quantum numbers of others s antis and gg states

[en] Hadrons produced in high-energy heavy-ion collisions can suppress the production of J/ψ and other charmonium states by charmonium spontaneous dissociation as the hot hadronic environment alters the interaction between the charm quark and charm antiquark. Furthermore, hadrons can thermalize a charmonium to excite it to higher charmonium states which subsequently dissociate spontaneously. They can also collide with a charmonium to lead to its prompt dissociation into an open charm pair

[en] In this introductory overview I will discuss recent developments in hadron spectroscopy that are of particular relevance to this meeting, including the spectroscopy of heavy quark hadrons, exotic and multiquark systems, and new theoretical results such as developments in LQCD. (author)

[en] In this paper we consider all possible 1D and 2P cc-bar assignments for the recently discovered X(3872). Taking the experimental mass as input, we give numerical results for the E1 radiative widths as well as the three principal types of strong decays; open-charm, cc-bar annihilation and closed-charm hadronic transitions. We find that many assignments may be immediately eliminated due to the small observed total width. The remaining viable cc-bar assignments are 1 ³D₃, 1 ³D₂, 1 ¹D₂, 2 ³P₁ and 2 ¹P₁. A search for the mode J/ψπ⁰π⁰ can establish the C parity of the X(3872), which will eliminate many of these possibilities. Radiative transitions can then be used to test the remaining assignments, as they populate characteristic final states. The 1 ³D₂ and 1 ¹D₂ states are predicted to have large (ca. 50%) radiative branching fractions to χ_c1γ and h_cγ, respectively. We predict that the 1 ³D₃ will also be relatively narrow and will have a significant (ca. 10%) branching fraction to χ_c2γ, and should also be observable in B decay. Tests for non-cc-bar X(3872) assignments are also discussed

[en] We report predictions for the energy eigenstates and inelastic neutron scattering excitations of an isotropic Heisenberg hexamer consisting of general spin S and S(prime) trimers. Specializing to spin-1/2 ions, we give analytic results for the energy excitations, magnetic susceptibility, and inelastic neutron scattering intensities for this hexamer system. To examine this model further, we compare these calculations to the measured magnetic susceptibility of a vanadium material, which is considered to be well defined magnetically as an isolated S = 1/2 V⁴⁺ trimer model. Using our model, we determine the amount of inter-trimer coupling that can be accommodated by the measured susceptibility, and predict the inelastic neutron scattering spectrum for comparison with future measurements.

[en] We report inelastic and elastic neutron scattering, magnetic susceptibility, and heat capacity measurements of polycrystalline sodium ruthenate (Na₃RuO₄). Previous work suggests this material consists of isolated tetramers of S = 3/2 Ru⁵⁺ ions in a so-called lozenge configuration. Using a Heisenberg antiferromagnet Hamiltonian, we analytically determine the energy eigenstates for general spin S. From this model, the neutron scattering cross-sections for excitations associated with spin-3/2 tetramer configurations is determined. Comparison of magnetic susceptibility and inelastic neutron scattering results shows that the proposed lozenge model is not distinctly supported, but provides evidence that the system may be better described as a pair of non-interacting inequivalent dimers, i.e double dimers. However, the existence of long-range magnetic order below Tc 28 K immediately questions such a description. Although no evidence of the lozenge model is observed, future studies on single crystals may further clarify the appropriate magnetic Hamiltonian.

[en] Fluoride phases that contain the spin-1/2 4d⁹ Ag(II) ion have recently been predicted to have interesting or unusual magnetochemistry, owing to their structural similarity to the 3d⁹ Cu(II) cuprates and the covalence associated with this unusual oxidation state of silver. Here we present a comprehensive study of structure and magnetism in the layered Ag(II) fluoride Cs₂AgF₄, using magnetic susceptometry, inelastic neutron scattering techniques and both X-ray and neutron powder diffraction. We find that this material is well described as a two-dimensional ferromagnet, in sharp contrast to the high-T_c cuprates and a previous report in the literature. Analyses of the structural data show that Cs₂AgF₄ is orbitally ordered at all temperatures of measurement. Therefore, we suggest that orbital ordering may be the origin of the ferromagnetism we observe in this material.

[en] This Conceptual Design Report (CDR) presents the compelling scientific case for upgrading the Continuous Electron Beam Accelerator Facility (CEBAF) at Jefferson Lab to 12 GeV. Such a facility will make profound contributions to the study of hadronic matter. In particular, it will allow breakthrough programs to be launched in four main areas: (1) The experimental study of gluonic excitations in order to understand the funda- mentally new dynamics that underpins all of nuclear physics: the confinement of quarks. Theoretical conjectures, now strengthened by lattice QCD simulations, indicate that the most spectacular new prediction of QCD - quark confinement - occurs through the formation of a string-like 'flux tube' between quarks. This conclusion (and proposed mechanisms of flux tube formation) can be tested by determining the spectrum of the gluonic excitations of mesons. (2) The Fundamental Structure of the Nuclear Building Blocks. A vast improvement in our knowledge of the fundamental structure of the proton and neutron can be achieved. Not only can existing 'deep inelastic scattering' cross sections be extended for the first time to cover the critical region where their basic three-quark structure dominates, but also measure- ments of new 'deep exclusive scattering' cross sections will open the door to a comprehensive characterization of these wavefunctions using the framework of the Generalized Parton Distributions; these data will provide access to information on the correlations among the quarks. These studies will be complemented by detailed measurements of elastic and transition form factors, determining the dynamics underlying the quark-gluon structure through measurements of their high-momentum-transfer behavior and providing essential constraints on their description. (3) The Physics of Nuclei. A broad and diversified program of measurements that (taken together with the hadron studies outlined above) aims to provide a firm intellectual under-pinning for all of nuclear physics by answering the question 'How does the phenomenological description of nuclei as nucleons interacting via an effective interaction parameterized using meson exchange arise from the underlying dynamics of quarks and gluons?' It has two main components: The emergence of nuclei from QCD. Experiments aimed at understanding how the description of nuclei in terms of nucleons interacting via the N - N force arises from the more fundamental QCD description. It includes the investigation of the partonic structure of nuclei, of short range structures in nuclei, and of the modification of the quark-gluon structure of the nucleons and mesons by the nuclear environment. Fundamental QCD processes in the nuclear arena. Experiments aimed at understanding how hadron-hadron interactions arise from the underlying quark-gluon structure of QCD. (4) Tests of the Standard Model of electro-weak interactions and the determination of fundamental parameters of this model. Precision, parity-violating electron scattering experiments made feasible by the 12 GeV Upgrade have the sensitivity to search for deviations from the Standard Model that could signal the presence of new physics. Precision measurements of the two-photon decay widths and transition form factors of the three neutral pseudoscalar mesons π⁰, η, and η' via the Primakoff effect will lead to a significant improvement on our knowledge of chiral symmetry in QCD, in particular on the ratios of quark masses and on chiral anomalies. This science program has expanded significantly since the project was first presented to the Nuclear Sciences Advisory Committee (NSAC) in the form of a White Paper [WP01] produced as part of the 2001-2002 NSAC Long Range Planning Process and since the pre-Conceptual Design Report (pCDR) produced in June 2004 to document the Upgrade science and experimental equipment plans [pCDR]. While focusing on science, this document also provides a brief description of the required detector and accelerator upgrades so that it can serve as an overview of the entire plan for the 12 GeV project. This CDR was developed from the documentation presented in the pCDR [pCDR] and further discussions within the community since that document was released. We acknowledge here the many contributions of the entire JLab community, and note that the author list at the end of the pCDR includes the names of all contributors to the effort known to us. Many of them commented extensively on the earlier drafts, resulting in a much-improved document. This document would have been impossible without their intelligence, enthusiasm, time, and just plain hard work.