Measurement of the gamma gamma partial width of the chi 2 charmonium resonance.

The E760 Collaboration has studied the reaction [ital [bar p]p][r arrow][chi][sub 2][r arrow][gamma][gamma] using a hydrogen gas jet target in the Fermilab antiproton acumulator ring. The following values are obtained for the branching ratio and partial width to two photons; [ital B]([chi][sub 2][r arrow][gamma][gamma])=(1.60[plus minus]0.45)[times]10[sup [minus]4] and [Gamma]([chi][sub 2][r arrow][gamma][gamma])=321[plus minus]95 eV.