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F. E. Close

Publications and source records attributed to F. E. Close.

46 records · Page 3Linked to original sources
arXiv1994

The Photoproduction of Hybrid Mesons from Cebaf to HERA

Decay widths, branching ratios and production dynamics of some recently discovered $J^{PC} = 1^{-+}, 0^{-+}$,$1^{--}$ and $2^{-+}$ mesons are found to be in remarkable agreement with the predicted properties of hybrid mesons. We propose tests for this new dynamics, emphasise the critical role of $πb_1$ or $πh_1$ decay channels in discriminating hybrids from conventional states, and suggest that photoproduction may offer special opportunities for isolation and confirmation of hybrids.

hep-ph↗
arXiv1994

The Production and Decay of Hybrid Mesons by Flux-Tube Breaking

An analytic calculation of the breaking of excited chromoelectric flux-tubes is performed in an harmonic oscillator approximation and applied to predict the dynamics of all $J^{PC}$ low-lying gluonic excitations of mesons (hybrids). Widths, branching ratios and production dynamics of some recently discovered $J^{PC} = 1^{-+}, 0^{-+}$ and $1^{--}$ mesons are found to be in remarkable agreement with these results. We introduce the selection rules that can be used to understand the systematics of numerical decay calculations and we find possible significant breaking of these rules for specific channels that may enable enhanced production and detection of hybrids.

hep-ph↗
arXiv1994

Searching for Exotic Mesons in e^+e^- Annihilation at Dafne

$DAΦNE$ should be useful for testing the nature of the vector mesons directly produced in $e^-e^+$ annihilation, as well as the nature of the $C=+$ states produced in the radiative decays of these vector mesons. In the $DAΦNE$ energy range, these latter states may have spin up to two and any parity. Provided the background can be handled and the spin of the produced state is known, the study of the angular distributions in these decays can measure the parity of the produced meson as well as the ratios of the independent production helicity amplitudes. These ratios provide sensitive tests for quark model classification of the states, in particular the enigmatic $f_1(1420)$. Thus, they can be used to indicate whether the mesons involved are consistent with the usual $q \bar q$ interpretation, or whether other interpretations like \eg\,hybrid, glueball or multiquark, are more favorable for some of them.

hep-ph↗
arXiv1994

Flavour Dependence of Form Factors in Heavy Meson Decays

Recently we have shown that due account of Wigner spin rotations is needed to match the ISGW model consistently onto HQET. We now discuss the flavour dependence of this procedure. We find that for finite mass ``heavy'' quark the universal function $ξ(y=1) \approx 1$ but the slope is proportional to the energy of the spectator quarks, and ratios of form factors are corrected in a way that QCD sum rules seem to require. Predictions for heavy quarks, such as in $B_c \rightarrow ψ(η_c)$ and to mixed systems, such as $D\rightarrow K$ and $B \rightarrow π$ show a systematic mass dependence that may be confronted with data.

hep-ph↗
arXiv1993

Quark Model Form Factors for Heavy Quark Effective Theory

We show how both the spectroscopy of heavy-light hadrons and the slope of the Isgur-Wise function can be simultaneously fitted when Heavy Quark Effective Theory is matched onto dynamical quark models, including careful treatment of wigner rotations. Working consistently to order $\vec{v}^2$ and using the parameters from hadron spectroscopy as input, we determine the slope parameter $ρ$ for s-wave transitions to be $1.19 \pm 0.02$. This agrees with the emperical value for $b \rightarrow c$ transitions.

hep-ph↗
arXiv1993

The Nucleon Spin Crisis Bible

When the new data on polarised lepton nucleon scattering are compared at the same value of $Q^2$ and with a common set of assumptions, a consistent picture of the spin content of the nucleon begins to emerge. Higher order effects in $0(α_s)$, higher twist effects, modern data on unpolarised structure functions and an updated value for F/D are all important in analysing the data. The detailed x dependences of the polarisation asymmetry in the valence quark region are shown to confirm 20 year old predictions of the quark model and I argue that these are an important ingredient in decoding the nucleon spin puzzle.

hep-ph↗
arXiv1993

Consistent Analysis of the Spin Content of the Nucleon

The recent measurements of lepton nucleon scattering with polarised neutron and deuteron targets are analysed together with the previous polarised proton data in a mutually consistent way. The detailed $x$-dependence of the polarisation asymmetry in the valence region is shown to be in agreement with historical predictions based on quark models. The Bjorken sum rule is shown to be confirmed at the $1σ$ level and estimates of the spin content of the nucleon $Δq$ are extracted. While the average value of $Δq$ from the three experiments comes out to be $0.41\pm0.05$ (to be compared with the naive quark model theoretical expectation of 0.58) this experimental average value is more than one standard deviation from the value obtained from any individual experiment.This inconsistency can be overcome by allowing arbitrary higher twist contributions but the resulting precision is poor, $Δq = 0.38\pm 0.48$.

hep-ph↗
arXiv1993

Probes of Heavy Meson Substructure in $e^+ e^-$ annihilation

We apply Heavy Quark Effective Theory to the production of $0^-$ and $1^-$ $Q\bar{q}$ states in $e^+ e^-$ annihilation. We show that HQET implies that the electric quadrupole amplitudes vanish and we propose tests for this theory. We also show how HQET can be applied to distinguish the $^3D_1$ and $^3S_1$ $Q\bar{Q}$ states.

hep-ph↗
arXiv1993

Scalar Mesons in $ϕ$ Radiative Decay: their implications for spectroscopy and for studies of CP-violation at $ϕ$ factories

Existing predictions for the branching ratio for $ϕ\rightarrow K\bar{K}γ$ {\it via} $ϕ\rightarrow Sγ$ (where $S$ denotes one of the scalar mesons $f_0$(975) and $a_0$(980)) vary by several orders of magnitude. Given the importance of these processes for both hadron spectroscopy and CP-violation studies at $ϕ$ factories (where $ϕ\rightarrow K^0 \bar K^0 γ$ poses a possible background problem), this state of affairs is very undesirable. We show that the variety of predictions is due in part to errors and in part to differences in modelling. The latter variation leads us to argue that the radiative decays of these scalar states are interesting in their own right and may offer unique insights into the nature of the scalar mesons. As a byproduct we find that the branching ratio for $ϕ\rightarrow K^0\bar{K}^0γ$ is $\lapproxeq 0(10^{-7})$ and will pose no significant background to proposed studies of CP-violation.

hep-ph↗