<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;">Hello All,<div><br></div><div>I took a quick look with GEMC to probe the edge where the full energy beam electrons hit the edge of the SVT vacuum system. </div><div><br></div><div>To the electron side (right) we grace the edge if the electron is at theta=7.8 degrees, phi=172.7 degrees. This causes a hit on the edge of the second column from the right, in row 2. So the last column is not accessible, see figure 1.</div><div><br></div><div>To the positron side (left) we grace the edge if the electron is at theta= 14.3 degrees, phi=8.3 degrees. This causes hits in the fifth column from the left, in row 2, so the left most 4 columns don't see full energy hits.</div><div><br></div><div>I would speculate that the hits in Luca's that were in the yellow region get some hits directly, and also some hits that graced the edge and so lost some energy, thus obscuring the nice peak.</div><div><br></div><div>Best,</div><div><span class="Apple-tab-span" style="white-space:pre"> </span>Maurik</div><div><br></div><div>Note: for the graphs below I set the GEANT4 cutoff energy at 40 MeV, so that only higher energy tracks are shown. This cleans up the picture a lot.</div><div><br></div><div><br></div><div><br></div><div><br></div><div><br></div><div><img apple-inline="yes" id="3467FDF8-157B-4A8A-A1A9-874D75EECF07" height="1241" width="650" apple-width="yes" apple-height="yes" src="cid:EE541144-A9FD-4DE3-8E85-A7734FC64B74@hsd1.me.comcast.net"></div><div><img apple-inline="yes" id="399C1681-8F1D-4F6B-A749-4BE93F4965D2" height="1271" width="693" apple-width="yes" apple-height="yes" src="cid:31231F52-65B1-4B61-853F-BB4E22141E81@hsd1.me.comcast.net"></div></body></html>