Light-quark meson photoproduction at a mean energy of 120 GEV/C

Author

Murali Pisharody

Date of Award

12-1993

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Physics

Major Professor

George T. Condo

Committee Members

William M. Bugg, Thomas Handler, Harry Y. McSween

Abstract

The purpose of this work is to investigate the following photoproduction reaction channels: (equations in PDF) where N and N' are nucleons appropriate for charge conservation. The data used for this analysis came from reconstructed tapes condensed from about 500 million triggered events written out by the E687 fixed target photoproduction experiment at FERMILAB during its 1990 and 1991 runs. Aside from the usual broad enhancement in the ρ’(1600) region, the neutral 4π channel shows evidence for a narrow peak in the vicinity of ~2.1 GeV. The resonant substructures in this channel are also investigated. The neutral dipion mass spectrum shows clear enhancements corresponding to ρ(770), ƒ₂(1270), and ρ₃(1690), and a J/ψ(3097) signal presumably through the misidentification of muons as pions. Also, a clear α,/i>₂(1320) peak is observed in the ρπ^± mass spectrum of the (3π)^± substructure. The dipion spectrum of the K⁺ K^- π⁺ π^- channel displays statistically significant signals of ρ(770) and ƒ₀(975) resonances. Only a clear ø(1020) peak is found in the dikaon spectrum of this channel (a bias was introduced on the dikaon mass during the original data skimming phase of the experiment). Evidence for a possible non-q&qmacr; state with a mass ~1930 MeV is found in the øρ mass spectrum and an apparent enhancement at ~2300 MeV is observed in the oslash;ƒ₀ mass spectrum. The J/ψπ⁺π^-(J/ψ → μ⁺μ^-) mass spectrum shows a clear ψ’(3685) resonance, the radially excited state of J/ψ(3097). Finally, an investigation of the dikaon spectrum in the neutral 4K channel shows peaks corresponding to ø(1020), ƒ’₂(1525), and a statistically weak enhancement near ~1.2 GeV perhaps due to the ƒ₀(1240). The overall neutral 4K mass spectrum, as well as the øø spectrum, show no evidence for any resonant structures.