ZZ versus ZH kinematics

I generated+simulated+reconstructed some ZZ samples with centre of mass energy = 230GeV. The files are in DST format. Soon I will  upload them to the grid.

From kinematics the energy of the Z bosons in ZZ process in the centre of mass frame is sqrt(s)/2. But because of the different masses of the Z and the Higgs bosons, the energy of the Z boson should be (s-mZ^2-mH^2)/(2*sqrt(s)). We can see that from the plot of the energy of the Z boson below. The blue line was obtained using ZZ+ZH samples whereas the dashed black is from ZH only. Cuts on the energy of the Z may be worth doing to remove also the ZZ background.

The next plot shows the recoil mass. The different cuts are in the plot (problems using math symbols here).