Limits on Electron-Neutrino Oscillations from the GALLEX ${}^{51}$Cr Source Experiment

The recent result from the chromium source experiment carried out by the GALLEX collaboration implies interesting limits on the parameters $\mathrm{\Delta }{m}^2$ and ${\sin }^{2}2\theta$ describing neutrino oscillations. Values of $\Delta m^2~>~0.17$eV$^2$formaximalmixingandof$\sin^22\theta > 0.38$for$\Delta m^2 > 1$eV$^2$ are ruled out at 90% C.L. This result improves by more than an order of magnitude previous limits on $\mathrm{\Delta }{m}^2$ derived from electron-neutrino oscillation experiments at accelerators.