[Sane-analysis] Minutes of Sept 15 2010 Analysis Meeting

[Narbe Kalantarians]

_*Hovhaness:*_ Studying the pair symmetric/positron background, looking 
mostly at the 5.9GeV perpendicular data (runs 72488-72500). Sees a small 
contribution (~4-8% @ E > 0.5GeV). Looking at invariant mass spectrum 
for pi0s, reconstructing for positrons, saw that the pi0 mass was off, 
centering around 100MeV. Swimming these specific pi0's back to somewhere 
in the Cerenkov (about 80 +/-5cm downstream from target) the mass is 
centered more towards the correct value. The suspicion is that this 
could be from something in the Cerenkov, perhaps the LED, its support 
structure, and/or mirror edge (from flipping open). Will try 
implementing this structure into the GEANT to see if it gets reproduced.
Looking at distance between cluster tracks as a function of pi0 mass and 
requiring that Lucite fires (both sides of TDC) seems to eliminate the 
pi0 mass peak. This implies that the Lucite wasn't firing that much 
meaning that what is being seen is mostly photons. This will require 
more investigation.
Looking at positron asymmetry for background contribution. They seem 
sizable but would be smaller with dilution (~50+%) being taken into 
account. These also include the beam and target polarization, which may 
need to be taken out and make it even smaller.


_*James:*_ Revisiting  front tracker studies, where he was projecting 
hits in BigCal back to the front tracker. Used most recent replay 
engine, with updated neural network taking slow raster into account. The 
results don't seem much different from last time. The tracking agrees 
well for the varying methods up to the radius of the tracker, but 
diverge after that. This will take some more looking into.
https://hallcweb.jlab.org/experiments/sane/wiki/index.php/Particle_Tracking_to_Front_Tracker%2C_Target#Revisiting_Front_Tracker:_9.2F15.2F2010
Updated scaler table, adding information about the scalers 508 and 536, 
as well as b1trig and b2trig (calculated by dividing the prescalers out 
of the values in the gen files).
https://hallcweb.jlab.org/experiments/sane/wiki/index.php/Dead_Time#Update_to_Scaler_Table:_9.2F15.2F2010


_*Jon:*_ Went through the Carbon runs to check for helium content. Did 
this by looking at the top and bottom target chip resistor resistances. 
Generally a resistance of 1200 Ohms or below indicates a warm target, 
and a resistance higher than 1300 Ohms indicates the presence of liquid 
helium. Prepared spreadsheet that gives the relevant information. This 
will be very helpful in the packing fraction effort.
https://hallcweb.jlab.org/experiments/sane/wiki/index.php/Carbon_Run_List
Checking livetimes calculated from variables in the ntuples relating to 
the helicity triggers. This is basically a sanity check to make sure 
things are working correctly. g_hel_pos(neg) is used in the analyzer 
code(sane_ntuple_keep) to count triggers positive and negative beta2 
triggers. btrigp(n) is used in CTP to count the same thing. These in 
combination with the gscaler(510 or 538) values are used to calculate 
the livetimes. They should (and appear to) output the same numbers, so 
the report template and the ntuple should give the same values for 
livetimes.


As always, please let me know if I forgot something or if I made any 
mistake(s).

Next meeting will be Sept 22.
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