Effect of triggering with the PMT on the DUT

Since we acquired our Photonis PMT I have been experimenting with it, and I noticed that the signals become noticeably smaller if I require the oscilloscope to trigger in coincidence between the LGAD and the PMT than if I trigger only on the LGAD. So I made a beta scan to see how important is this effect in a histogram. I describe my experience in this document which I embed below