Single and multi-photon events with missing energy in e+e− collisions at 161 < < 172

A search for single and multi-photon events with missing energy is performed using data collected at centre-of-mass energies between 161 GeV and 172 GeV for a total of 20.9 pb$^{-1}$ of integrated luminosity. The results obtained are used to derive the value for the $\nu\bar{\nu}\gamma(\gamma)$ cross section as well as upper limits on new physics processes.