[Halld-offline] HDGeant4 Meeting Minutes, May 4, 2021
marki at jlab.org
Mon May 10 16:33:15 EDT 2021
Please find the minutes here
HDGeant4 Meeting, May 4, 2021, Minutes
Present: Alex Austregesilo, Tegan Beattie, Sean Dobbs, Mark Ito (chair),
Igal Jaegle, Richard Jones, Zisis Papandreou, Lubomir Pentchev, Simon
Taylor, Nilanga Wickramaarachchi, Beni Zihlmann
There is a recording of this meeting
<https://bluejeans.com/s/smXkAPjiI7L/> on the BlueJeans site. Log into
the BlueJeans site <https://jlab.bluejeans.com> first to gain access
(use your JLab credentials).
Review of minutes from the last meeting
We went over the minutes from the meeting on April 6
Tegan will continue his studies using the software for analysis launch
version 38 with its wider timing window, dropping back from version 40.
He will get it running on the JLab farm.
Simulating Hit Efficiency for the FDC
Lubomir presented Garfield studies
which he derives hit efficiency as a function of distance from the wire.
This work was previously presented at the Tracking Meeting.
He showed an example track passing through a cell (page 2) which
demonstrates the variation in drift trajectories. He showed the
efficiency as a function of DOCA for various track angles (page 3). Here
there is not much variation in the behavior as a function of angle. The
main source of inefficiency is that for large drift distances,
ionization arrives at the wire over an extended time, due to diffusion
(page 4). That in turn leads to a lower peak pulse height even though
the integrated charge collected may not be much different from
ionization that travels a shorter distance. The lower peak pulse height
may not cross the hit threshold, causing the hit to be lost. One
consequence is that the efficiency has a strong dependence on the
At present, in the simulation this effect is not there. Any reduction in
efficiency will come only from tracks having a small path inside a cell.
In simulation, this explains the much sharper drop in efficiency as a
function of DOCA compared to that seen in Lubomir's result.
Richard pointed out that there is an energy threshold of sorts applied
in HDGeant4 on energy loss in a cell summed over all particles that
traverse the cell (multiple tracks from the event, or accidentals), but
this does not take into account the reduced probability of threshold
crossing due to large diffusion for long drift distances.
Lubomir's plots show the coefficients of his parametrization of
efficiency. Richard will take a stab at incorporating the efficiency
curves into mcsmear.
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