sPHENIX HCal discussion

[Edward Kistenev <kistenev AT bnl.gov>]

Hi, John, 

I am done with 2017 testing of tile to tile uniformity. Cosmic data in some form are  available for 24 tiles of HInner calorimeter. After all other testing and tweaking 12 tiles of one configuration (S30)  were used to equalize the channel gains in the CAEN box I am currently using. They were then removed and 12 new randomly chosen tiles of a different configuration (S32)  were then placed into the same kluge.  Both data taking runs were made under the same running conditions and resulted in essentially identical numbers (peak positions, see two pictures below - before and after).  The ratio is 1.01 with rms of 10%. This is essentially a very good upper limit to configuration dependence of the light yield and tile-to-tile spread we have for the small tiles in the recent batch as it came from UNIPLAST. Its contribution to HInner induced constant term is certainly lower then that “estimated” as due to 20% across the tile non-uniformity or LCG fluctuations in calorimeter with depth dependent sampling fraction (which can be accounted for on event-by-event basis). 

My best guesstimate for today is that we do not need tile grouping for this prototype, visual inspection of fiber luminosity when tile is out of its protective wrap should be sufficient to answer live/dead question after shipment. 

And we will definitely pay attention to tile-LED data when they will be available in January.

Edward  

On Dec 20, 2017, at 4:32 PM, John Lajoie <lajoie AT iastate.edu> wrote:

Dear HCAL'ers:

    In the HCAL meeting today we had a discussion of the assembly of the inner HCAL for the test beam, the testing of the tiles, and whether or not it would be valuable to try to match cosmics response of the HCAL tiles within a tower.  In principle this should be a "good thing", and I would imagine that if there is a large variation between the tiles in a tower that could contribute to the constant term in the energy resolution.

    Doing this would require mating the scintillators with their SiPM's followed by cosmics testing to mix-and-match the scintillators before they are installed. It's my understanding that at BNL they will be ready to start installing scintillator soon, so if we want to do this then we need to get organized quickly.  Of course, we would only be doing this for the inner HCAL as the outer HCAL is the same as last year.  I think I would be assassinated if I suggested we disassemble the outer HCAL and match the tiles.

    In past test beams the variation within a tower was not carefully controlled, so if we did this it would be a good way to test the effect on the energy resolution. However, if we only do it for the inner HCAL it is likely of limited utility.

    Comments? Suggestions?

Regards,
John Lajoie

John Lajoie

Professor of Physics

Iowa State University

 

(515) 294-6952

lajoie AT iastate.edu

Contact me: john.lajoie

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