minutes from Feb 2, 2005

["Michael (Mike) Wood" <mikewood@jlab.org>]

Those in attendence: Eugene Pasyuk, Mark Ito, Ilia Larin, Eric Clinton, 
Yelena Prok, Marvin Payen, Dustin McNulty, David Lawrence, Mike Wood

1) Group discussed changing the time from 1pm on Weds. to something 
else.  Mark will send out an email to finalize the time.

2) Epics skims - Dustin reports that they are progressing fine.  He has 
to fill in a few files which were lost to autodeletion.

3) Bookkeeping - run numbers needed are Tac(Eric), e+e-(Ilia), 
compton(Yelena) which will be provided by the names in the paratheses.  
Ilia asked for the total number of events per run to be added to the 
db.  Dave said he remembers an old code on the clon machines which can 
calculate the numbers quickly.

4) CVS on the web - Mark is waiting for the computer center to change 
permissions on the server to allow anyone to see the primex software cvs 
tree on the web.

5) Livetime - Eugene gave a brief talk on how to calculate the livetime 
needed for the flux calculation.  The information is in the SCALER bank 
which saved scaler sums from the Trigger Supervisor.  In this bank, 
there are LIVE1(gated clock) and LIVE2(ungated clock).  The Livetime is  
LIVE1/LIVE2.

LIVE1 and LIVE2 can also be derived from the TRIGGER bank and one must 
be aware of the trigger latch for the events stored in the TRIGGER bank.

A 2nd method for calculating the livetime is the event-based one.  Here 
the livetime is
(# of accepted events)/(total triggers).  Mark suggested for the next 
data taking to have an external scaler module beside the ones in the 
trigger supervisor.

A 3rd method suggested by Dave is to sum the accepted events for each 
trigger latch fromt he TDCs in the TRIGT bank.

Eugene suggested that anyone can read the CLAS_NOTE 2005-002 to learn 
about the CLAS method of calculating the flux.

6) Veto bug - Mike stated that he found a bug in the Veto reconstruction 
routine(which he wrote) which assigned the wrong sign to the 
x-position.  When the bug was fixed, the charged-particle detection 
efficiency increased from 20% to 96% for a pair production run.  The 
changes were committed to CVS.