Meeting 2 February 2010
Meeting was attended by Alice B, Mike B and Ilya S. We discussed the current status of the filter. A brief summary of action items:
(1)No complaints so far to raising gamma maker thresholds to correspond to 2009 l2 trigger thresholds, which will probably remain the same for some time. These new thresholds are a seed threshold of 4.2 and a cluster threshold of 5.5 Email sent to list about this here. Currently the pythia filter thresholds are set 4 sigma lower than this and bfc filter thresholds are set 2 sigma lower than this. These will changed accordingly. FYI: definition of sigma from EEMC NIM paper is sigma(E)/E = 16%/sqrt(E)+2%. Note: the current gamma maker thresholds are 3.6 and 5.1, from the 2006 trigger configuration.
(2)We discussed current performace of pythia filter. Suspect some increased rejection may come from tighening eta boundaries in the filter along with radius of the cluster cone in eta-phi space. Mike also suggested adding a vertex cut for the particle track vertices. This kind of cut currently exists in the bfc filter. We think these changes need to tested, along with the changes in (1) before we move forward. Ilya will check what the vertex cut in his analysis is.
(3)Small scale tests of the bfc filter with the 2 sigma thresholds are promising and not showing false rejections.
(4)A (too) small scale test of the thresholds in (1) showed no acceptance in the 2-3 GeV partonic pT bin. Will run more events to verify it is excluded. Concerned that we will probably not be able to eliminate the 3-4 GeV bin. Alice would not like to set the gamma maker cluster et threshold above 6. Agreed, and that maybe even that is too high.
(5)We discussed the issue of the gain uncertainty in the filter. The concern is that a filter which is "too tight" will exclude events that we will need for testing the gain uncertainty in a final analysis. There are multiple concerns here :
i. How to actually do this. Jason sent a suggestions that would involve modifying the fundtion StEEmcSlowMaker::setTowerGainSpread(float s) to include a variable MEAN, which is currently hard-coded to 1. The new code would look like:
void StEEmcSlowMaker::setTowerGainSpread(Float_t s, Float_t MEAN)
{
// initialize tower gain factors to 1
for ( Int_t sec=0;sec<kEEmcNumSectors;sec++ )
for ( Int_t sub=0;sub<kEEmcNumSubSectors;sub++ )
for ( Int_t eta=0;eta<kEEmcNumEtas;eta++ )
{
// mTowerGainFact[sec][sub][eta]=1.0;
Float_t f = -1.0E9;
while ( f <= -1. || f >= 1.0 )
f = gRandom->Gaus(0., s);
mTowerGainFact[sec][sub][eta] = MEAN + f;//this was 1.0+f
}
}
this requires a change to the code, but it is small and MEAN could be set by default to 1.0 Then we would re-process the gamma trees with the slow simulator set with MEAN = 1-1sigma uncertainty and MEAN=1+1sigma uncertainty and test the rejection of the filter. Ilya would like to see this code checked into cvs, which would require someone with karma - probably Oleksandr.
ii. What number to use for the uncertainty. It seems that 5% is widely accepted as correct. Please object if you think this is wrong. Please object if you think this method is not sufficient to test the filter with uncertain gains.