Search for high massγγ resonances in\(e^ + e^ - \to \ell ^ + \ell ^ - \gamma \gamma \) ,\(\nu \bar \nu \gamma \gamma \) and\(q\bar q\gamma \gamma \) at LEP Iat LEP I

A search for high mass photon pairs from the processes\(e^ + e^ - \to \ell ^ + \ell ^ - \gamma \gamma \),\(e^ + e^ - \to q\bar q\gamma \gamma \) and\(e^ + e^ - \to \nu \bar \nu \gamma \gamma \) with the DELPHI detector at LEP I is reported. From a data sample containing 3.5 million hadronic Z0 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 GeV/c2, where 76±6 events were predicted from standard sources. In the same data sample, no\(\nu \bar \nu \gamma \gamma \) candidates were found and no accumulation of events was visible forγγ masses above 10 GeV/c2 in the\(q\bar q\gamma \gamma \) channel. Upper limits at 95% confidence level on the Z0 branching ratios for the three different channels were extracted from the data. In the mass regionm γγ >30 GeV/c2 the limits obtained are between 3×10−6 and 4×10−6.