arXiv subjects
Publications and source records attributed to F. E. Close.
LHCb measurements of $B_{d,s} \to J/ψ+ X$ are shown to be consistent with historical data on scalar and axial mesons below 2 GeV. This is in contrast to some recent interpretations of these data. Further tests of our hypotheses in other $B_{u,d,s} \to J/ψ+ X$ decay modes are suggested.
Charm meson molecule (c\bar n)(n\bar c) assignments for the supercharmonium state Z(4475) are considered, both on general grounds and in the context of specific pion exchange models. Two possible charm molecule assignments for the JP = 1+, Z(4475) are considered here, involving respectively a radially and an orbitally excited charm meson. In each assignment, a lower-mass isosinglet charm molecule state is predicted. For both the Z(4475) and the Y(4260), measurement of the ratios of the branching fractions to D \bar D plus n pions is recommended as a test of the nature of these states.
We explore quark-hadron duality in semi-inclusive pion electroproduction on proton and neutron targets. Using the spin-flavor symmetric quark model, we compute ratios of pi+ and pi- cross sections for both unpolarized and polarized scattering, and discuss realizations of duality in several symmetry breaking scenarios. The model calculations allow one to understand some of the key features of recent data on semi-inclusive pion production at low energies.
We investigate how coupling of valence q qbar to meson pairs can modify the properties of conventional q qbar and hybrid mesons. In a symmetry limit the mixing between hybrids and conventional q qbar with the same J^PC is shown to vanish. Flavor mixing between heavy and light q qbar due to meson loops is shown to be dual to the results of gluon mediated pQCD, and qualitatively different from mixing involving light flavors alone. The validity of the OZI rule for conventional q qbar and hybrid mesons is discussed.
We show that the literature on pion exchange between charm and bottom mesons is inconsistent. We derive the formalism explicitly, expose differences between papers in the literature and clarify the implications. We show that the X(3872) can be a bound state but that results are very sensitive to a poorly constrained parameter. We confirm that bound states in the B Bbar sector are possible. The circumstances whereby exotic combinations can bind with cc or bb quantum numbers are explored.
We generalize results of lattice QCD to determine the spin-dependent symmetries and factorization properties of meson production in OZI allowed processes. This explains some conjectures previously made in the literature about axial meson decays and gives predictions for exclusive decays of vector charmonia, including ways of establishing the structure of Y(4260) and Y(4325) from their S-wave decays. Factorization gives a selection rule which forbids $e^+e^- \to D^* D_2$ near threshold with the tensor meson in helicity 2. The relations among amplitudes for double charmonia production $\e^+e^-\to ψχ_{0,1,2}$ are expected to differ from the analagous relations among light flavour production such as $\e^+e^-\to ωf_{0,1,2}$.
We derive relations among branching fractions in the exclusive decay of charmonia to light flavour meson pairs assuming factorization between the quark spin and spatial degrees of freedom. With the further assumption that these amplitudes can be described by flux-tube models, we assess prospects for production of hybrid mesons in charmonium decays.
The spectrum and decay properties of radially excited $D_s$ states are examined in a new model. Good agreement is obtained with the properties of two recently announced $D_s$ mesons identified as $D_{s0}(2860) = c\bar{s}(2P)$ and $D^*_{s}(2690) = c\bar{s}$ as a possible mixture of $(2S;{}^3S_1)$ and $(1D;{}^3D_1)$. Searching for these mesons in B decays is advocated due to large predicted branching ratios.
Flux tube model predictions for hybrid meson decays are beginning to be confronted by Lattice QCD. We compare the two approaches for the $S$-wave decay of the exotic $1^{-+}$, and find excellent agreement. Results suggest that in Strong QCD, \qq~ creation occurs with S=1.
Recent signals for narrow hadrons containing heavy and light flavours are compared with quark model predictions for spectroscopy, strong decays, and radiative transitions. In particular, the production and identification of excited charmed and cs states are examined with emphasis on elucidating the nature of $0^+$ and $1^+$ states. Roughly 200 strong decay amplitudes of $D$ and $D_s$ states up to 3.3 GeV are presented. Applications include determining flavour content in $η$ mesons and the mixing angle in $P$ and $D$ wave states and probes of putative molecular states. We advocate searching for radially excited $D_s^*$ states in B decays.
The recent data for $J/ψ$ hadronic decays from BES raise ``puzzles" about the scalar meson properties, which are different from the naive OZI rule expectation. In this work, we study the implications of a glueball-$Q\bar{Q}$ mixing scheme in the scalar meson productions in $J/ψ$ hadronic decays. We show that the significant OZI violations in $J/ψ\to V f_0^i$ ($i=1,2,3$ correspond to $f_0(1710)$, $f_0(1500)$ and $f_0(1370)$, respectively) are consistent with the requirement of strong glueball-$Q\bar{Q}$ mixings within the scalar meson wavefunctions.
States beyond those expected in the simple constituent quark model are now emerging. I focus on the scalar glueball and its mixing with states in the $q\bar{q}$ nonet, and also on correlations in Strong QCD that may form diquarks and seed $qq\bar{q}\bar{q}$ states. Some models of the pentaquark candidate $Θ(1540)$ are critically discussed.
If the exotic baryon $Θ^+(1540)$ is a correlated $udud\bar{s}$ with $J^P = {1/2}^+$, then there should exist an exotic meson, $J^P = 1^-$ $\vartheta^+ (S=+2)$ $\to K^+K^0$ $\sim 1.6$GeV with width $O(10-100)$MeV. The $π_1(1400;1600)$ may be broad members of {\bf 10} $\pm$ \10bar in such a picture. Vector mesons in the 1.4 - 1.7GeV mass range are also compared with this picture.
The observation of $π_1(1600) \to πρ$ is shown in the flux-tube model to be compatible with this state being a hybrid meson with branching ratio to this channel $\sim 30%$. The $πρ$ widths of other hybrids are related by rather general arguments. These results enable cross sections for photoproduction of hybrids to be predicted.
We consider possible assignments for the D$_{s\J}^+(2632)$, which was recently reported in D$_s^+η$ and D$^0$K$^+$ final states by the SELEX Collaboration at Fermilab. The most plausible quark model assignment for this state is the first radial excitation ($2^3§_1$) of the $c\bar s$ D$_s^*(2112)$, although the predicted mass and strong decay branching fractions for this assignment are not in agreement with the SELEX data. The reported dominance of D$_sη$ over DK appears especially problematic. An intriguing similarity to the K$^*(1414)$ is noted. $2^3§_1$--$^3\D_1$ configuration mixing is also considered, and we find that this effect is unlikely to resolve the branching fraction discrepancy. Other interpretations as a $c\bar s$-hybrid or a two-meson molecule are also considered, but appear unlikely. Thus, if this state is confirmed, it will require reconsideration of the systematics of charmed meson spectroscopy and strong decays.
We identify essential differences between the pentaquark and chiral soliton models of \10bar$_5$ and {\bf 8}$_5$ pentaquarks and conventional {\bf 8}$_3$ states, which are experimentally measurable. We show how the decays of $Ξ_5$ states in particular can test models of the pentaquarks, recommend study of the relative branching ratios of e.g. $Ξ^{-}_5 \to Ξ^-π^0:Ξ^0π^-$, and predict that the decay amplitude $Ξ_5 \to Ξ^*π$ is zero at leading order in pentaquark models for any mixture of \10bar and the associated {\bf 8}$_5$. We also include a pedagogic discussion of wavefunctions in the pentaquark picture and show that pentaquark models have this {\bf 8}$_5$ with $F/D=1/3$, in leading order forbidding $Ξ_5 \to ΛK$. The role of Fermi-Dirac symmetry in the $qqqq$ wavefunction and its implications for the width of pentaquarks are briefly discussed. The relative couplings $g^2(Θ_Q N K_Q^*)/g^2(Θ_Q N K_Q) = 3$ for $Q \equiv s,c,b$. A further potentially narrow state $Λ$ in {\bf 8}$_5$ with $J^P = 3/2^+$ is predicted around 1650 MeV.
If the exotic baryon $Θ(1540)$ is $udud\bar{s}$ with $J^P = {1/2}^+$, we predict that there is a \10bar with $J^P = {3/2}^+$ containing a $Θ^*(1540-1680)$. The width $Γ(Θ^* \to KN)$ is at least a factor of three larger than $Γ(Θ)$. The possibilities of $Θ^* \to KNπ$ or $Θγ$ via $M1$ and $E2$ multipoles are discussed.
Recent data on charmonium production in B-meson decays suggest that charmonium hybrid mesons with mass ~4 GeV may be produced in B-decay via c\bar{c} colour octet operators. Some of these states are likely to be narrow with clean signatures to J/ψpi^+ pi^- final states. Experimental signatures and search strategies for existing B-factories are described.