Search for high mass $\gamma\gamma$ resonances in $e^+e^- \rightarrow l^{+}l^{-}\gamma\gamma\nu\overline{\nu}\gamma\gamma$ and q$\overline{q}\gamma\gamma$ at LEP I

A search for high mass photon pairs from the processes ${\mathrm e}^+ {\mathrm e}^- \to \ell^+ \ell^- \gamma \gamma\ $, ${\mathrm e}^+ {\mathrm e}^- \to {\mathrm \nu} \overline {\mathrm \nu} \gamma \gamma\ \mathrm e}^+ {\mathrm e}^- \to {\mathrm q} \overline {\mathrm q} \gamma \gamma\ $ and with the DELPHI detector at LEP I is reported. From a data sample containing 3.5 million hadronic ${\mathrm Z^0}\;$ decays, collected by DELPHI during the years 1991 to 1994, 79 events with two charged leptons and two isolated photons were selected with photon pair masses above 10 $\mathrm{GeV}/c^2\ $, where 76 $\pm\ $ 6 events were predicted from standard sources. In the same data sample, no ${\mathrm \nu} \overline {\mathrm \nu} \gamma \gamma\ $ candidates were found and no accumulation of events was visible for $\gamma \gamma\ $ masses above 10 $\mathrm{GeV}/c^2\ $ in the ${\mathrm q} \overline {\mathrm q} \gamma \gamma\ $ channel. Upper limits at 95\% confidence level on the ${\mathrm Z^0}\;$ branching ratios for the three different channels were extracted from the data. In the mass region $m_{\gamma \gamma}\ $ $ $ 30 $\mathrm{GeV}/c^2\ $ the limits obtained are between \mbox{3$\times 10^{-6} $}and \mbox{4$\times 10^{-6} $}.