Leptonic decays and kaon identification at the NA62 experiment at CERN

A study of the radiative leptonic K+ ! e+neg kaon decay is reported, using a partial sample of data collected by the NA62 experiment at CERN in 2007. The signal event selection, the study of trigger efficiencies and the measurement of form factors are presented. The main systematic uncertainties associated to the analysis are discussed and preliminary results on form factor parameters are obtained: V0 = 0.0946 0.0018stat 0.0170syst l = 0.521 0.055stat 0.052syst with a statistical correlation between parameters of 􀀀0.94 and 100% correlation between systematic errors. The outcome of a test run performed at CERN in October 2011 for the commissioning of a Cherenkov differential counter to be used for the charged kaon identification in the near-future NA62 research programme, is reported. The counter’s ability to distinguish between kaons and pions is validated by pressure scan results. Tests of various combinations of standard and new read-out technology and electronics are presented. The time resolution of the new photon detector technology (Hamamatsu R7400-U03 PMT) to be replaced for the detector upgrade in NA62 is measured: sT = (251 2)ps . 3