A New Measurement of the $\ddot{I}{€}^0$ Radiative Decay Width

Abstract

High precision measurements of the differential cross sections for $\ddot{I}{€}^0$ photoproduction at forward angles for two nuclei, ${}^{12}$C and ${}^{208}$Pb, have been performed for incident photon energies of 4.9 - 5.5 GeV to extract the $\ddot{I}{€}^0\to {\hat{I}}^3{\hat{I}}^3$ decay width. The experiment was done at Jefferson Lab using the Hall B photon tagger and a high-resolution multichannel calorimeter. The $\ddot{I}{€}^0\to {\hat{I}}^3{\hat{I}}^3$ decay width was extracted by fitting the measured cross sections using recently updated theoretical models for the process. The resulting value for the decay width is $\hat{I}“(\ddot{I}{€}^0\to {\hat{I}}^3{\hat{I}}^3)=7.82\pm 0.14(stat.)\pm 0.17(syst.)\mathrm{eV}$. With the 2.8% total uncertainty, this result is a factor of 2.5 more precise than the current PDG average of this fundamental quantity and it is consistent with current theoretical predictions.

4 pages, 5 figures