<html><head><meta http-equiv="Content-Type" content="text/html charset=windows-1252"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;"><div><br></div><div>Hi Will,</div><div><br></div><div> I was chatting with Elton today about your presentation at the calorimetry meeting this morning.</div><div>I’m sorry I missed it. From my discussion with Elton and from what we talked about at the </div><div>Calibration meeting on Wednesday, it sounds like the simulation of the dark hits is simply</div><div>giving a much larger contribution that what we are seeing in the real detector. This likely due</div><div>to the conversion factors used to convert photo-electrons and energy into mV not being correctl. </div><div>As was discussed, these factors need to be adjusted in order to bring the simulation into better</div><div>agreement with the real data. </div><div><br></div><div> The relevant factors in mcsmear/smear_bcal.cc are the following shown with their current values:</div><div><br></div><div><font face="Courier">BCAL_mevPerPE = 0.668338<br>mV_per_MeV = 0.881599 </font><br><br></div><div> The value of mV_per_MeV is inversely proportional to BCAL_mevPerPE (the latter being used</div><div>in the calculation of the former). The dark hit amplitude and the signal amplitude are both multipled</div><div>by mV_per_MeV. Only the dark hits though are proportional to BCAL_mevPerPE. What this </div><div>means is than in order to adjust the relative amplitude between signal and dark hits, without</div><div>changing the signal size in mV, both of the above parameters have to be modified.For example,</div><div>to effectively reduce the dark hit amplitude by a factor of 10 relative to the signal, we divide </div><div>both BCAL_mevPerPE and mV_per_MeV by 10 in the code:</div><div><br></div><div><font face="Courier">BCAL_mevPerPE /= 10.0 => 0.0668338<br> mV_per_MeV /= 10.0 => 0.881599 </font><br></div><div><br></div><div>note that the value of mV_per_MeV doesn’t actually change since the value of BCAL_mevPerPE</div><div>is used to calculate it.</div><div><br></div><div>I’ve made a few plots to show a comparison of with and without this change. You can see for the </div><div>second plot (the logY one) that the signal part of a cell energy (above about 75MeV) is not</div><div>affected much. There is significant reduction in the lower energy part though. The last plot shows</div><div>the reconstructed cluster energy. This indicates a drop of about 10% in the reconstructed</div><div>energy (simulation was all 1GeV photons). I think this is what you were alluding to when you</div><div>said simply removing the dark hits from the cells with signal caused issues since the reconstruction</div><div>has been tuned to put the peak at the right place when dark hits are present. Either those parameters</div><div>will need to be re-tuned, or the value of mV_per_MeV scaled by a smaller factor than BCAL_mevPerPE.</div><div><br></div><div>The scale factor of 10 was arbitrary and the actual factor should probably come from a comparison</div><div>to the real data. I think we have two handles by which to do that. The first is the number of hits (first</div><div>plot). We could reproduce that plot with “no-signal” events and adjust the scaling factor until it matches</div><div>what we see from data taken with the detector using a random trigger. The second would be to convert</div><div>GeV into Pulse Integral fADC units and look at the “dark hits pedestal” width. This would again need</div><div>to be done with no-signal data. Hopefully, the same scale factor will give agreement in both, though</div><div>we may need to tweak the threshold to get that.</div><div><br></div><div>I’m not sure how much time you have to work on this so we can discuss how best to proceed.</div><div><br></div><div>Regards,</div><div>-David</div><div><br></div><div><br></div><div><br></div><div><img apple-inline="yes" id="3CAC271B-9572-46D0-BC66-57E4061EE165" height="472" width="696" apple-width="yes" apple-height="yes" src="cid:E1DA2C92-1F29-4EAB-B1BE-5FD60928BECB"></div><div><br></div><div><br></div><div><br></div><div><img apple-inline="yes" id="839ED839-87F0-4B71-8660-A133A5F6762B" height="472" width="696" apple-width="yes" apple-height="yes" src="cid:FD21D8B1-2F48-4DF0-B61B-039B1BAEF38D"></div><div><br></div><div><br></div><div><br></div><div><br></div><div><img apple-inline="yes" id="615F0CB8-DF78-4002-95BA-D44387B6B73A" height="472" width="696" apple-width="yes" apple-height="yes" src="cid:72941798-DD44-4BFC-B159-7549F42E0D69"></div><div><br></div><div><br></div><div><br></div><div><br></div><div><img apple-inline="yes" id="A4763807-06F6-45C2-AFA4-3FC0487C6F30" height="472" width="696" apple-width="yes" apple-height="yes" src="cid:C24766F8-BBB9-45DD-96E8-D76571BC8076"></div><div><br></div><div><br></div><div><br></div><div><img apple-inline="yes" id="6AAB5B22-722C-4B33-95B5-B4E774B236E5" height="472" width="696" apple-width="yes" apple-height="yes" src="cid:189617C0-1E2D-4E70-84F6-FF7B12E5CBBE"></div><div><br></div><div><br></div></body></html>