This paper gives results for the spectrum, all allowed E1 radiative partial widths (and some important M1 widths) and all open-charm strong decay amplitudes of all 40 cc states expected up to the mass of the 4S multiplet, just above 4.4 GeV. The spectrum and radiative widths are evaluated using two models, the relativized Godfrey-Isgur model and a nonrelativistic potential model. The electromagnetic transitions are evaluated using Coulomb plus linear plus smeared hyperfine wavefunctions, both in a nonrelativistic potential model and in the Godfrey-Isgur model. The open-flavor strong decay amplitudes are determined assuming harmonic oscillator wavefunctions and the 3 P0 decay model. This work is intended to motivate future experimental studies of highermass charmonia, and may be useful for the analysis of high-statistics data sets to be accumulated by the BES, CLEO and GSI facilities.

Open-flavor strong decays are mediated by qq pair production, which is known to occur dominantly with 3 P 0 quantum numbers. The relation of the phenomenological 3 P 0 model of these decays to ''microscopic'' QCD decay mechanisms has never been established clearly. In this paper we investigate qq meson decay amplitudes assuming pair production from the scalar confining interaction (sKs) and from one gluon exchange ͑OGE͒. sKs pair production predicts decay amplitudes of approximately the correct magnitude and D/S amplitude ratios in b 1 → and a 1 → which are close to experiment. The OGE decay amplitude is found to be subdominant in most cases, a notable exception being 3 P 0 → 1 S 0 ϩ 1 S 0 . The full sKs ϩ OGE amplitudes differ significantly from 3 P 0 model predictions in some channels and can be distinguished experimentally, for example, through an accurate comparison of the D/S amplitude ratios in b 1 → and a 1 →.

In this paper we survey all radial and orbital excitations of the Iϭ0 and Iϭ1 nn system anticipated up to 2.1 GeV. We give detailed predictions of their quasi-two-body branching fractions and identify characteristic decay modes that can isolate quarkonia; this should be useful in distinguishing quarkonia from glueballs and hybrids. Several of the ''missing mesons'' with L q q ϭ2 and L q q ϭ3 are predicted to decay dominantly into certain Sϩ P and SϩD modes, and should appear in experimental searches for hybrids in the same mass region. We also consider the topical issues of whether some of the recently discovered or controversial meson resonances, including glueball and hybrid candidates, can be accommodated as quarkonia.

Heisenberg antiferromagnetic spin "ladders" (two coupled spin chains) are low-dimensional magnetic systems which for S = 2 interpolate between half-integer-spin chains, when the chains are decoupled, and effective integer-spin one-dimensional chains in the strong-coupling limit. The spin-2 ladder may be realized in nature by vanadyl pyrophosphate, (VO)2P207. In this paper we apply strong-coupling perturbation theory, spin-wave theory, Lanczos techniques, and a Monte Carlo method to determine the ground-state energy and the low-lying excitation spectrum of the ladder. We find evidence of a nonzero spin gap for all interchain couplings J&)0. A band of spin-triplet excitations above the gap is also analyzed. These excitations are unusual for an antiferromagnet, since their long-wavelength dispersion relation behaves as (kko) (in the strong-coupling limit J~))J, where J is the in-chain antiferromagnetic coupling). Their band is folded, with a minimum energy at ko =m, and a maximum between kl =~/2 (for J~= 0) and 0 (for J& =~). We also give numerical results for the dynamical structure factor S(q, co), which can be determined in neutron scattering experiments. Finally, possible experimental techniques for studying the excitation spectrum are discussed.

In this paper we consider all possible 1D and 2 P cc 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 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 assignments are 1 . A search for the mode J/ 0 0 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 3 D 2 and 1 1 D 2 states are predicted to have large ͑ca. 50%͒ radiative branching fractions to c1 ␥ and h c ␥, respectively. We predict that the 1 3 D 3 will also be relatively narrow and will have a significant ͑ca. 10%͒ branching fraction to c2 ␥, and should also be observable in B decay. Tests for non-cc X(3872) assignments are also discussed.

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In this paper we evaluate strong decay amplitudes and partial widths of strange mesons (strangeonia and kaonia) in the 3 P 0 decay model. We give numerical results for all energetically allowed open-flavor two-body decay modes of all ns and ss strange mesons in the 1S, 2S, 3S, 1P, 2P, 1D and 1F multiplets, comprising strong decays of a total of 43 resonances into 525 two-body modes, with 891 numerically evaluated amplitudes. This set of resonances includes all strange qq states with allowed strong decays expected in the quark model up to ca. 2.2 GeV. We use standard nonrelativistic SHO quark model wavefunctions to evaluate these amplitudes, and quote numerical results for all amplitudes present in each decay mode. We also discuss the status of the associated experimental candidates, and note which states and decay modes would be especially interesting for future experimental study at hadronic, e + e − and photoproduction facilities. These results should also be useful in distinguishing conventional quark model mesons from exotica such as glueballs and hybrids through their strong decays. *

We discuss the implications of a possible quasinuclear DK bound state at 2.32 GeV. Evidence for such a state was recently reported in D s ϩ 0 by the BaBar Collaboration. We first note that a conventional quark model cs assignment is implausible, and then consider other options involving multiquark systems. An Iϭ0 csnn baryonium assignment is one possibility. We instead favor a DK meson molecule assignment, which can account for the mass and quantum numbers of this state. The higher-mass scalar cs state expected at 2.48 GeV is predicted to have a very large DK coupling, which would encourage formation of an Iϭ0 DK molecule. Isospin mixing is expected in hadron molecules, and a dominantly Iϭ0 DK state with some Iϭ1 admixture could explain both the narrow total width of the 2.32 GeV state as well as the observed decay to D s ϩ 0 .Additional measurements that can be used to test this and related scenarios are discussed.