Measurement of the Reactions e + e − → e + e − and e + e − →γγ at \sqrt s =52 GeV

The differential cross sections for e + e - → e + e - and e + e - →γγ have been measured at the highest energy of \(\sqrt{s}=52\) GeV in e + e - collisions.The process e + e - → e + e - is well understood within the framework of the standard model of electroweak interactions. The reaction e + e - →γγ is found to be in good agreement with QED. The 95% confidence limits obtained for the QED cut-off parameters are \(\varLambda_{+}>61\) GeV and \(\varLambda_{-}>72\) GeV for e + e - →γγ.