Further results in the search for the direct two-proton decay of $^{94}$Ag$^{m }$(J$^{\pi }$= 21$^{+}$, 6.7 MeV)

Both direct one-proton decay and direct two-proton decay of $^{94}$Ag$^{m}$ from this 0.4 s isomeric state have been reported in experiments utilizing the GSI on-line mass separator [1]. In the latter decay, coincident events between silicon E detectors with a threshold energy of 0.4 MeV and a summed decay energy of 1.9$\pm $0.1 MeV were observed with a yield of 350$\pm $210 pb in coincidence with $\gamma $-decays in the $^{92}$Rh daughter. We utilized our helium-jet system at the LBNL 88-inch cyclotron to repeat this experiment, again employing the $^{58}$Ni($^{40}$Ca,p3n) reaction at 197 MeV. Reaction products were transported via a capillary to a detection area and collected on a slowly rotating wheel in front of an assembly of 24 $\Delta $E$_{gas}-\Delta $E$_{gas}$-E$_{Si}$ detector telescopes with a threshold of 0.4 MeV for identifying protons. Five of these telescopes observe the 0.79 MeV single proton decay from $^{94}$Ag$^{m}$ at the reported yield of 1.3 nb. In the 240/276 identified proton detector combinations with low background, no proton-proton coincidences have been observed. Data from the remaining 36 detector combinations require a separate analysis, which is in progress. Monte Carlo analyses of our anticipated proton-proton coincidences for both sets of detector combinations will be presented. $^{ 1}$Mukha et al., Nature \underline {439}, 298 (2006).