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Hi,

the problem was a feature. The SVT readout simulation didn't always provide a SVT collection (if empty) and could unsync the truth. The second thing  is that the  readout simulation now includes a readout dead time which is longer than the 250 empty bunches we artificially put in. This means that when we stack triggers on average 250 BC apart we will loose some of those because of this dead time. The solution is to use more empty bunches (1000). I will verify that it looks good.

/Pelle

On Sep 21, 2012, at 9:23 AM, Hansson Adrian, Per Ola wrote:

> Hey,
> 
> as promised I'm working on implementing truth particle matching (incl. propagation). 
> 
> I got confused when looking at some basic properties of the truth vs reco objects. 
> 
> This is what I'm doing:
> - Run slic
> - Run filtering with 250 empty bunches
> - Run readout simulation (incl. trigger simulation as usual)
> 
> If I plot the number of tracks vs event number I see that there is no "250 BC gap" between the events. Is this because the event numbers are not "sticky" so that my reco files start numbering events has been reset to 1,2,3,4?
> 
> I made sure that these events are totally dominated by e+e- with <1% events with anything else. With that said I can do very simple check of the truth matching since I know that if we have a negative (positive) track reconstructed in the event it should be *the* electron (positron), there is nothing else going on in the event and the number of ghost tracks should be very small.
> 
> What I see however is that in an event where I have a positive (negative) track reconstructed, I only find a positron (electron) in ~30% of the cases. I would expect that to be close to 100%? 
> 
> I also checked so that there isn't a sign flip convention (last two rows in the busy canvas attached)
> 
> For the cases where there is a "match", the momentum seems totally uncorrelated between the truth and track (4th row in the busy canvas attached).
> 
> Could we have a problem in the way we keep track of the truth in these events so there is a mismatch between truth and reco event numbers?
> 
> I should say that looking only at the truth or only and the reco the distributions look ok.
> 
> One thing I need to look at is the vertical angle of the truth particles to make sure that one of them is responsible for firing the trigger (although this wouldn't tell anything about if there is a mismatch between the truth and reco event).
> 
> Cheers,
> 	
> 	Pelle
> 
> 
> <Screen Shot 2012-09-21 at 8.42.28 AM.png><Screen Shot 2012-09-21 at 8.42.17 AM.png><Screen Shot 2012-09-21 at 8.41.06 AM.png>


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