[Halld-offline] [EXTERNAL] Re: HDGeant4 Meeting Minutes, November 29, 2021

[Shepherd, Matthew]

I don't think this is plausible:

At 2 degrees the absolute maximum variation in x or y position that the energy can induce is:  45 cm * tan( 2 degrees ) = 1.5 cm, which would occur if the energy error caused the z position to move from the front face of the block to the back face of the block (impossible!).  In reality the systematic error in z due to energy calibration errors is much smaller than the size of the block and likely produces an insignificant change in position on the scale of what is required for FCAL track matching.

Matt


> On Nov 30, 2021, at 12:07 PM, Igal Jaegle <ijaegle at jlab.org> wrote:
> 
> Correction.
> 	• Data/MC discrepancy in FCal Matching around Beam Hole
> 		• The energy is not used, only the time and position in this context. -> The energy is used since not only the time is used but also the position determined using the energy.
> 
> 
> 
> tks ig. 
> From: Halld-offline <halld-offline-bounces at jlab.org> on behalf of Mark Ito <marki at jlab.org>
> Sent: Monday, November 29, 2021 5:20 PM
> To: halld-offline at jlab.org <halld-offline at jlab.org>
> Subject: [Halld-offline] HDGeant4 Meeting Minutes, November 29, 2021
>  
> Folks,
> Please find the minutes here and below,
>   -- Mark
>      _________________________________
> HDGeant4 Meeting, November 29, 2021, Minutes
> 
> Present: Alex Austregesilo, Sean Dobbs, Mark Ito (chair), Igal Jaegle, Richard Jones, Simon Taylor, Beni Zihlmann
> There is a recording of this meeting on the BlueJeans site. Log into the BlueJeans site first to gain access (use your JLab credentials). 
> Announcement
> 
> There will be a meeting at 4 pm tomorrow to discuss preparations for the upcoming Computing Review.
> Review of minutes from the last meeting
> 
> We went over the minutes from the meeting on November 15. Richard repeated his report of a possible issue where timing signals from the FCAL do not agree between data and MC. There was a report of seeing accidental peaks in the raw timing histograms in simulation where in data they do not appear. Richard explained that In data, one needs to subtract the RF to get peaks; in simulation, if one does the same thing, the seen-in-raw-hits peaks persist. By doing time difference to time-difference comparisons, there is no mystery, and these are the only comparisons we should be doing anyway. He is waiting for confirmation of this understanding from the folks who raised the issue.
> Issues on GitHub
> 
> We looked at the Issues. 
> 	• Data/MC discrepancy in FCal Matching around Beam Hole
> 		• Other than that difference in track matching to the FCAL in data vs. simulation, initially noted by Alex, Igal raises a lack of calibration of 2017 data for the inner blocks.
> 		• It is not clear that a fiducial cut is needed to exclude inner blocks from their role as a backup t-zero setter for tracking. The energy is not used, only the time and position in this context.
> 		• Sean will review the status of the 2017 calibration.
> 	• Crash adding daughters on RHEL/CentOS 8
> 		• We think this one is resolved but are still waiting for Hao Li to confirm the fix.
> 	• Add incident angle dependence to DIRC mirror reflectivity
> 		• This enhancement remains on the books. Richard will consult with the DIRC folks to see if they have done any further thinking on this. In principle, implementation is straightforward.
> 
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