sPHENIX HCal discussion

[Edward Kistenev <kistenev AT bnl.gov>]

Hi, Megan,

I looked through your transparencies, thanks, they are good as always. 

I have few questions or comments (unlikely to be able to connect today):

- what is the excess thickness added to tiles by the edge wrap, it looks totally against anything we discussed with tech’s before my disappearance (especially over the corners). Is it on both sides or one only. Were tile-thickness measurements done on that band or inside that band. If on the band - can you repeat them in points inside the band and compare;

- can light leak measurements be repeated on tiles without that extra light insulation.

About LED’s. You are probably asking too much from LED’s. They will work as calibration devices in one sense only - to measure single pixel amplitude and use it as a calibration for the gain of electronics. There is no reason or purpose to expect LED’s to produce the same amplitude in every tile, but they should allow the amplitude control to bring all LED signals into the range of few pixels (maybe in different events). Trying to find solution which will allow them all to be close is just an overkill, channel energy calibration may come from Cosmic events or beam events (like in calorimeters today) only, everything else is not even approximation. I think your results on identity of response to cosmic are excellent in this sense.

Finally - I am very worried by discussion about what is below the SiPM coupler. I wrote so many mails about the need to have the bulk light suppression blend between tile and SiPM but it looks as if all of it was totally ignored. If it is not done - out Inner section may become a tail-generator (not easy to simulate), it is less important in the Outer HCal where fiber-SiPM coupling area is far from the shower maximum.

Edward 

Edward Kistenev, PhD

PHENIX Physicist