D. Aschman

Use of a Low Energy Proton Accelerator for Calibrating a Large NaI(Tl) Array in a High Energy Physics Experiment

We report the use of a 500 keV Van de Graaff proton accelerator to produce ¿-rays in the range 4 - 18 MeV via nuclear reactions for the purpose of calibrating a large NaI(Tl) crystal array. Data analysis indicates an energy calibration to ~ 1% over this range.

Recent results from the crystal ball detector at SPEAR

Evidence for an ηc candicate with a mass of 2980±15 MeV from the ψ′ inclusive γ spectrum is presented. The corresponding region in the J/ψ inclusive γ spectrum is then studied and shown to be consistent with a broad Breit‐Wigner enhancement superimposed upon a smooth background. Results from a detailed study of the two exclusive decay modes ψ′→γγ ψ→γγ e+e− and ψ′→γγ ψ→γγμ+μ− are also given. These consist of measurements of the cascade branching ratios BR(ψ′→γχ→γγψ) for χ(3.55) and χ(3.51) and upper limits on this branching ratio for χ(3.41), χ(3.45), and χ(3.59). Finally, we give branching ratios for the two decays ψ′→ηψ and ψ′→π °ψ.