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combinations of pid algorithms [message #13489] 
Wed, 16 May 2012 15:31 
Dmitry Khaneft
Messages: 75 Registered: January 2009

continuous participant 
From: *kph.unimainz.de


Dear all,
I have another issue. I tried different combinations of PID algorithms and found out a strange thing.
For example if I use following code with "PidAlgoEmcBayes" enabled only
theAnalysis>FillList(eplus, "ElectronVeryTightPlus","PidAlgoEmcBayes");
or another one with many others included
theAnalysis>FillList(eplus, "ElectronVeryTightPlus","PidAlgoEmcBayes;PidAlgoStt;PidAlgoMvd;PidAlgoDrc;PidAlgoDisc;PidAlgoMvd");
then the first case gives me less events compare to the second one. It seems very strange for me. I would expect that by adding new algorithms I should be getting less rather then more events.
Cheers,
Dmitry




Re: combinations of pid algorithms [message #13492 is a reply to message #13490] 
Wed, 16 May 2012 15:42 
Dmitry Khaneft
Messages: 75 Registered: January 2009

continuous participant 
From: *kph.unimainz.de


Stefano Spataro wrote on Wed, 16 May 2012 15:36 
Why? If you multiply your initial pdf with another pdf, you will obtain a different probability distribution. I cannot see a direct correlation of drop in efficiency with increasing number of algorithms.

Sorry may be I was not clear. It is exactly what I would expect but for some reason my results are opposite. Efficiency goes up with increasing number of algorithms.
[Updated on: Wed, 16 May 2012 15:43] Report message to a moderator




Re: combinations of pid algorithms [message #13494 is a reply to message #13489] 
Wed, 16 May 2012 15:53 
Dmitry Khaneft
Messages: 75 Registered: January 2009

continuous participant 
From: *kph.unimainz.de


Hm. I was following tutorial and found these lines
Quote: 
...
theAnalysis>FillList( looseElectrons, "ElectronLoose", "PidAlgoEmcBayes;PidAlgoDrc;PidAlgoMvd");
In this case the probabilities for PID selection are achieved by multiplying the probability values of the chosen algorithms, i.e. Pe = Pe,1 × Pe,2 × Pe,3, etc.

The only case one can get increase in efficiency is if one of the probabilities >1 what is impossible. Am I right?
[Updated on: Wed, 16 May 2012 15:53] Report message to a moderator





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