Fraction of electrons in the T9 pion beams

In the T9 beam line, the beam instrumentation does not permit the separation of electrons from pions, except for the 1:5, 3 and 5 GeV/c beam momenta. For beam momenta of 8 GeV/c or higher, the flux of beam electrons must be subtracted from the flux of pion-like particles incident on the target in order to obtain correct pion interaction cross-sections. In this memo, data from the beam instrumentation and the electron-identifier in `empty-target' runs are analysed in order to determine the fraction of electrons incident on the target, in the pion beams from 1.5 to 15 GeV/c.