[Halld-pid-upgrade] [Revised Logentry] Early results from DIRC Follow-up Re: First DIRC commissioning with beam

[jrsteven at jlab.org]

Logentry Text:
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After setting the timing offset and window yesterday we were able to see both the LED and physics triggers in the DIRC timing distribution, and occupancies on the PMT plane match roughly those expected from MC simulations of bggen events (neglecting for now the pixel-by-pixel efficiencies).  Below are plots of the PMT time distribution and occupancy for Run 60591 data (left) and bggen MC (right).

[figure:1]

[figure:2]

After some rough timing calibrations, we were able to correlate charged tracks with DIRC PMT hits using the Look Up Table (LUT) algorithm.  Below are more comparisons between data and MC for several distributions comparing values (based on the charged track information) and measured values (from the DIRC PMT hits).  In particular, in the plot below we see that the measured time of the hit is correlated with the expected time (although with a wider time distribution

[figure:3]

For these PMT hits that are in a wide time window of +/- 8 ns, the difference between the expected and measured Cherenkov angle is plotted in the figure below.  In the MC the peak is narrower, but this at least indicates that the LUT algorithm is measured reasonable thetaC values in the data at this point.

[figure:4]

More to come as we dig deeper into the data and tune the MC parameters, but initial indications are that the commissioning data we took last night is already in reasonable shape.


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