sPHENIX tracking discussion

["Huang, Jin" <jhuang AT bnl.gov>]

Hi Joe and all

Closing the loop on the clock frequency used in Run24/25 reconstruction: 

From John Haggerty that the RF group measured 3x RHIC clock to be 28128770.729 Hz. And Hugo and I measured the 2x FEE ADC clock to RHIC clock ratio to be 4.262916255. 

We don't need that much precision for tracking reconstruction, but 0.1% precision is needed to keep track of the clocks cross 500x beam crossing over one trigger window. So here is my recommendation on the clock setting in the code, carrying more digits of significant than we need: 

• TPC ADC Time Bin in Run24 = 19985099 Hz or 50.037280 ns 
• TPC ADC Time Bin in Run25 = 18752514 Hz or 53.326184 ns
• RHIC beam collision clock = 9376257 Hz or 106.65237 ns  <- the change from pp and AuAu is negligible for our purpose 

Note the drift speed and T0 likely need adjustment by the same ratio once the clock frequency is changed in our calibration database. 

Cheers

Jin

 

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Jin HUANG

 

Physicist, Ph.D.

Brookhaven National Laboratory

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