A Study of the Iota in Radiative J/PSI Decays

Citation

Richman, Jeffrey David (1985) A Study of the Iota in Radiative J/PSI Decays. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/09yd-ka21. https://resolver.caltech.edu/CaltechETD:etd-10162008-153536

Abstract

An analysis of the production, decay, and quantum numbers of the ι(1440) in radiative J/Ψ decays is presented. The ι(1440), because of its large production in this OZI-suppressed channel, is considered a possible gluonic bound-state, or glueball. Such states appear to be a natural consequence of the non-Abelian structure of the SU(3) color gauge group of QCD. The data, 2.7 x 10⁶ produced J/Ψ's, were obtained using the Mark III detector at the SPEAR e⁺e^- storage ring.

The spin-parity of the ι(1440) is independently determined to be 0^- using two decay modes, ι → K⁰_SK^±π^∓ and ι → K⁺K^-π⁰. The technique used is based on the three-body helicity formalism, which provides a means of studying the decay angular distributions in a manner independent of the structure of the Dalitz plot. This is particularly useful in the case of ι → KK̅π, where the limited phase space makes it difficult to unambiguously identify the two-body modes. In addition, the measured angular distributions provide direct visual evidence supporting the spin-parity assignment. Measurements of the ι mass, width, and branching fractions are obtained using ι → K⁰_SK^±π^∓, ι → K⁺K^-π⁰, and ι → K⁰_SK⁰_Sπ⁰. The relative branching fractions are consistent with the isospin 0 predictions. From a study of the KK̅π Dalitz plot, an upper limit for ι → K^*K̅+ c.c. is obtained. These results are discussed in the context of the current experimental status of the E(1420).

Upper limits are presented for B(ι → ηππ), B(ι → δπ → ηππ), B(ι → KK̅ππ), and B(ι → ρππ). The limit on B(ι → δπ → ηππ) appears to be inconsistent with a large value of B(ι → δπ → KK̅π). However, the very uncertain status and properties of the δ(980) make it difficult to pinpoint the source of this inconsistency. Together, these upper limits provide evidence that, apart from a possible ι → ρρ signal, KK̅π is the dominant ι decay and that inclusive ι production is dominated by J/Ψ → γι, ι → KK̅π.

The double radiative channels J/Ψ → γX, X → γ+ Vector, where Vector = ρ⁰, φ, ω are studied to probe the quark content of the object X. Many pseudoscalar mixing models predict that the ι acquires a large radiative width into γρ⁰ through mixing with the η and η'. In the γ(γρ⁰) final state, a broad structure is observed in the 1.4 GeV region. Although the measured angular distributions are consistent with the pseudoscalar predictions, the central mass of this structure is below that found for the ι in the KK̅π channels. Thus, with the present limited statistics, it is unclear whether this structure should be identified with the ι. Upper limits are obtained for ι → γφ and ι → γω. Measurements are also obtained for B(J/Ψ → γη') and B(J/Ψ → γη) using the γ(γπ⁺π^- final state. These results are compared with theoretical predictions.

Measurements of the hadronic decays J/Ψ → φη, ωη, and ωπ⁰, as well as the observation of the isospin-violating decay J/Ψ → ρ⁰η, are presented.

Finally, the two- and three-body helicity formalisms are discussed in the Appendices.

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