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#### Followups:

keyword=Left arm scint. efficiency

The T4 rate is slightly higher than the T3 rate. Since T4 measures
efficiency, usually and to 1st order, this raises a red flag. I'm
not aware if anyone checked it, so here it goes. The "bottom line"
is that the scintillator efficiency is acceptably high (98-99%) and
for some reason a lot of T4 are junk. Note, the T1/T2 picture is
different.
```
Using a randomly chosen production run (2948)...

Examine the trigger efficiency for Left Arm using a plot like this:
===================================================================
T->Draw("L.vdc.u1.nhit+L.vdc.v1.nhit+L.vdc.u2.nhit+L.vdc.v2.nhit","fEvtHdr.fEvtType==3&&(L.vdc.u1.nhit+L.vdc.v1.nhit+L.vdc.u2.nhit+L.vdc.v2.nhit)>0");

And requiring either event type type 3 or 4, and judging if the event is "good" or "bad" from the sum of VDC hits >0  or  ==0  respectively.

From Raw Scaler Rates:
T3 raw rate = 174 Hz
T4 raw rate = 194 Hz   (--> implies naive inefficiency 53% !!)

Fraction of T3 which are good = 23665 / (3518+23665) = 87%
Fraction of T4 which are good = 70 / (70+2327)  = 2.9 %

Estimated Trigger Inefficiency = (0.029 * 194) / (0.87 * 174) = 3.7 %
==> Single scintillator plane Inefficiency = 1.8 %

This is about a factor of 2 higher than experience.  But one can do the same cleanup using L.tr.n (# of tracks).  Result is

Fraction good T3 = 84 %  (have >= 1 track)
Fraction good T4 = 1.5%
Trigger Ineff = 2.0%
Single-plane Ineffic = 1.0%

A  1% single-plane inefficiency is about what I expect.
```