4. Effect of the DEA cut on the missing mass distribution

If the DEA cut functions correctly and vetoes events with photons that have missed the LGD, we expect to see an effect of the DEA cut on the missing mass distribution.

The events with missing photons will tend to have a missing mass greater than the mass of the proton/neutron, so we would expect the DEA cut to remove events with high missing mass and keep events with low missing mass.

Three distributions are shown on figure 1. The unshaded plot shows the distribution of the square of the missing mass for a typical sample of 1995 14 GeV 0-2-2-LGD events with one positive, one negative charged tracks, and two photons. The plot with horizontal stripes shows the events removed by the DEA cut. The plot with 45 degree stripes shows the events kept by the DEA cut.

mmsqr-dea4.ps
mmsqr-dea4.ps.1.gif
Figure 1: Missing mass squared

The conclusion is that the DEA cut is working more or less as expected.