[d2n-analysis-talk] Comparison of DL.bit3 to DL.LT3

[David Flay]

Hi Brad,

Making a plot of these two variables separately, each having the same cuts:

VDC: One track, one cluster reconstruction in each plane
PID: GC > 300, E/p > 0.54, GC TDC cuts
Trigger: Remove the dead time pulser

Shows a similar structure, but there's more entries in DL.LT3 -- and
everything is shifted up a couple hundred channels.

Now, if we consider how the evtypebits is built (looking at the DecData
class),

//_____________________________________________________________________________
void THaDecData::TrigBits(UInt_t ibit, BdataLoc *dataloc) {
// Figure out which triggers got a hit.  These are multihit TDCs, so we
// need to sort out which hit we want to take by applying cuts.

  if( ibit >= kBitsPerByte*sizeof(UInt_t) ) return; //Limit of evtypebits
  bits.ResetBitNumber(ibit);

  const UInt_t cutlo = 200;
  const UInt_t cuthi = 1500;

  for (int ihit = 0; ihit < dataloc->NumHits(); ihit++) {
    if (dataloc->Get(ihit) > cutlo && dataloc->Get(ihit) < cuthi) {
      bits.SetBitNumber(ibit);
      evtypebits |= BIT(ibit);
    }
  }

//______________________________________________________________________________

which shows that the evtypebits is set whenever we have a hit in the TDC
within the cut window (for the variable DL.bitN, I believe).   So events
that fall within the cut window are the good ones -- whereas, looking at
the DL.LTN plot, we see entries beyond the cut window (on the high end,
especially).  What I'm thinking is, when using the DL.LTN plot, is that
I'm counting these entries, which may not, in fact, be good events...
Further, if we look at the DL.LT4 plot (see attached), there's a lot more
events registered here (that are <barely> outside the cut window of 200 -
1500, on the low end.  This of course, will drive down the T3 efficiency.

In any case, the evtypebits variable isn't constructed from the DL.LTN
plot anyway, correct?

Based on this, I think the correct variable to be using in the T3 Trigger
(for good electrons) Efficiency study is the DL.bitN variable.


-------------------------------------------------
David Flay
Physics Department
Temple University
Philadelphia, PA 19122

office: Barton Hall, BA319
phone: (215) 204-1331

e-mail: flay at jlab.org
            flay at temple.edu

website: http://www.jlab.org/~flay
              http://quarks.temple.edu
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