Study of radiative leptonic events with hard photons and search for excited charged leptons at GeV

During the last 1995 data acquisition period at LEP, the DELPHI experiment collected an integrated luminosity of 5.9 pb⁻¹ at centre-of-mass energies of 130 GeV and 136 GeV. Radiative leptonic events (e, μ, τ) with high energy photons were studied and compared to Standard Model predictions. The data were used to search for charged excited leptons decaying through an electromagnetic transition. No significant signal was found. From the search for pair produced excited leptons, the limits m_e^* > 62.5 GeV/c², m_μ^* > 62.6 GeV/c² and m_τ^* > 62.2 GeV/c² at 95% confidence level were established. For single excited lepton production, upper limits on the ratio λ/m_l^* of the coupling of the excited charged lepton to its mass were derived.