[d2n-analysis-talk] live time calculation

[posik at jlab.org]

Hi Brad,

  I am doing a live time calculation for the T5 trigger. I am doing this
by using the following formula

  T5_livetime = (t5cnt)/(t5_scnt)

 where t5cnt is the number of events with a T5 trigger after prescale (ie
evtypebits&1<<5==1<<5)

and t5scnt is the scaler T5 count, which is the difference between the t5
scaler count for the last and first event.

Now since we have a deadtime pulser plugged into the T2 and T3 triggers I
imagine this is also in the T5 trigger. Therefore I need to subtract it
off as follows

T5_livetime = (t5cnt-eldtpcnt)/(t5scnt-eldtpscnt)

where eldtpcnt are the events with an electric dead pulse and eldtpscnt is
the scaler electric dead time count.

For my eldtp varibles I use Ndata.DL.edtpbb (DL since this is a coin run)
and for the scaler I was not too sure what to use, so I used the scaler
called eldtm. Both the BB and LHRS had this scaler in their respective 
crates.

Is this the correct scaler to use with the Ndata.DL/DBB.edtpbb and
DL.edtpl variables?

using this edtp subtraction I get a Live time of ~80% for run 1258.
checking that end of run file it lists the dead time as

DEAD TIME: [ 0]:  15.31%      [++]:  18.98%      [--]:  18.92%      [+-]: 
18.93%      [-+]:  18.97%

Which if Livetime = 1-Deadtime, then there is ~5% difference.

I am also calculating ~ 0.014C/run

Thanks
Matt