Lepton Identifying issues

[iris]

Dear Experts,

I was generating p p > z z, z > e+ e- , z > vl vl~ using MG-Pythia-Delphes interface with default delphes card. I was expecting 2 electrons in my events but only 30% of the events contains 2 electrons. Later, I changed all the efficiency to 1 and isolation to perfect, still only 50% of the events contains 2 electrons. That does not seem right to me.

Could you please tell me how to enhance the lepton identifying efficiency?