sPHENIX HCal discussion

[Stefan Bathe <bathe AT bnl.gov>]

Dear All,

Here some notes from today’s meeting:

Simulation

---------------

- Ejiro presented on her muon gun simulation; suggestions:

  - Stefan:  change muon energy from 2 GeV to 4 GeV (https://cosmic.lbl.gov/SKliewer/Cosmic_Rays/Muons.htm)

  - Megan:  double check geometry calculation to make sure the gun is outside of the sector (i.e. take sector surface into account)

  - Justin:  sample position of gun to cover entire tower face and beyond (b/c of non-vertical angles) and sample cosmics angular distribution (cos^2)

    - Stefan:  to keep this simple it should be sample gun position along x-z plane (i.e. constant y) for the two towers in question (while being outside of the top tower at all times).  Then the muon will go through 0 to a few cm of steel before entering the tower of interest.  But that won’t matter since a 3.8 GeV muon is still a MIP and the energy of cosmics varies anyway.

- Saif reported that he has also started to look into the simulation.

Fitting

————

- Hanpu showed slides on fits of the ADC distributions of cosmics events with a gamma distribution + Gaussian for the low-ADC background.  He reported that the fits don’t fit the peak region well.

(Hanpu, please send me your slides so I can upload them to the agenda.  I still can’t find you on indico.  I think in addition to filling out Gunther’s survey, you also need to create an indico account.)

- Shuhan showed slides on peak finding of the ADC distributions.  It seems to work well.  Stefan pointed out that the bin width smears the peak information.  Bill said that this was a quantitative question in relation to the statistical uncertainty of the peak position, and they haven’t looked into that yet.

- Veronica showed slides on fitting with a Landau (or Landau convoluted with Gauss) plus Gauss for the low-ADC background (as suggested last time to replace the linear background), now also avoiding the overflow peak.  She reported that the fit is not automatic since the background description often fails.  Stefan suggested to simplify the fit by restricting it to the core of the peak and skipping the background part.

(Veronica, please post your slides on the agenda.)

- Conclusion:  fit all towers with peak finder and Landau (in parallel); compare towers in non-production sectors (where V = V_op) and in production sectors (where V .ne. V_op) among each other, respectively.  Also, correct gain in production sectors to make up for V .ne. V_op accordingly, and then compare all towers (both production and non-production).  (Veronica understands which sectors need the gain correction.)  Eventually, replace data for production sectors with new data taken during burn-in where V = V_op.

Other Business

---------------------

- Dan posted a catalogue of run numbers and HCal geometry info that Stefan presented briefly.  We can ask Dan to go through this at the end of the next HCal meeting.  (Stefan uploaded the files to the agenda after the meeting.)

- Justin asked about LED and cosmics data for estimating computing needs.  The data is at rcf:  /gpfs/mnt/gpfs02/sphenix/data/data02/sphenix/hcal/912

- Justin also asked about a db to store calibration parameters.  Dan Lis may looks into this, learning from Jeffrey Ouellette what was done for the EMCal.  Bill pointed out that the HCal db should be identical to the EMCal db if at all possible, which everybody agreed upon.

- Stefan brought up the question of a comics data taking during sPHENIX running.  Jamie had suggested to discuss this at the meeting.  Xiaochun pointed out that this would be useful.  Megan reported that the calibration task force thinks we should no rely on cosmics data taking during running for calibration (more statistics from tracks, etc.), but that we should not preclude the possibility to take cosmics.  Jamie had pointed out that event displays may be useful to look into trigger options.  It was suggested that the simulations group may have a tool to make event displays.  Stefan wrote an email to Chris and Jin.

 

- Xiaochun pointed out that there is an analysis not on cosmics analysis and promised to look for it.

- John Lajoie set another note during the meeting. 

- It was suggested to create an HCal calibration wiki page and collect the info there.  Stefan started that and added John’s note:

https://wiki.bnl.gov/sPHENIX/index.php/HCal_Calibration

Regards,

Stefan

 

On May 13, 2021, at 9:54 AM, Stefan Bathe <bathe AT bnl.gov> wrote:

Dear All,

A few weeks ago, several of us have started to get together informally to work on the HCal muon calibration.  To make this more inclusive, we decided to announce this on the list.  We will try to meet regularly in the HCal meeting time slot on Tuesdays, 11:00am, on the off weeks—at least for the near future.  So we’ll meet again next Tuesday, May 18, at 11:00am:

https://indico.bnl.gov/event/11854/

The purpose of this effort is two-fold:

1) Analyze the cosmics calibration data taken in 912 and see if we can understand them, and also use them for detector QA before the HCal installation.

2) From those data, translate the ADC response of the detector to cosmic muons to energy with help of a Geant simulation. 

Regards,

Stefan

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