[Halld-tagger] [EXTERNAL] PR submitted to halld_recon master for TAGM

[Richard Jones]

Hello Sean and all,

I have submitted a PR to the master branch that provides the ability to
require tdc hits on all DBeamPhotons created from TAGM hits. Here are some
features of my proposed solution.

   1. executing this PR and rebuilding on the master branch will produce NO
   IMMEDIATE difference in the way the hits factories behave, for any run
   period;
   2. once the libraries are built with the change installed, there are two
   ways to enable the requirement that TAGM photons have an associated adc +
   tdc.
      - assign a negative value to /PHOTON_BEAM/microscope/integral_cuts
      for the desired run range -- can also be on a subset of columns
if desired
      but this usage is not in view right now.
      - if ccdb contains a positive threshold in integral_cuts for a given
      run, you can still force the tdc requirement by running with commandline
      option -PTAGMHit:CUT_FACTOR=-1.

The tdc requirement is an effective pulse height cut at the level of the
discriminator. It never makes sense to require BOTH a pulse integral cut
AND the tdc requirement on the same channel, and the use of negative values
makes this blunder impossible, while making better use of the existing
integral_cuts table in ccdb rather than introducing a new table. It also
has the advantage that it gives a consistent behavior to how the TAGM
reconstruction was done for past run periods, which already have positive
values in this table in ccdb.

Once this fix is adopted, which I think it should be, the decision can be
made on a run-period by run-period basis where this tdc requirement should
be applied going forward, simply by writing new negative values to this
integral_cuts table in ccdb.

-Richard Jones
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