MadAnalysis 5

Signal over background ratio

Asked by S.S.

Dear sir,

I read in the manual of MA that there are three formulas of SBratio : S/B, S/B+S, and S/sqr{S+B}. Where S and B are the number of the signal events and bkg events respectively . May I ask how to determine which formula should I use in my analysis ?

Also I was studying some signal have energetic final states, and when I made cut on the transverse energy to reject events almost less than 200 GeV (besides other cuts on the mass ranges), all the Bkg events became zero .. is this right analysis ? I mean is it possible to have B = zero and to have after cuts only the signal events ? according to the second and third SBratio the signal efficiency still finite ..

Thanks,
Safinaz

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Launchpad Janitor (janitor) said : 		#1

This question was expired because it remained in the 'Open' state without activity for the last 15 days.

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Benjamin Fuks (fuks) said : 		#2

Dear Safinaz,

> I read in the manual of MA that there are three formulas of SBratio : S/B, S/B+S, and S/sqr{S+B}. Where S and B are the number
> of the signal events and bkg events respectively . May I ask how to determine which formula should I use in my analysis ?
The treatment of this has changed in the last version of the code. Please have a look here:
   http://madanalysis.irmp.ucl.ac.be/raw-attachment/wiki/WikiStart/MA5%20v1.4.pdf

> Also I was studying some signal have energetic final states, and when I made cut on the transverse energy to reject events
> almost less than 200 GeV (besides other cuts on the mass ranges), all the Bkg events became zero .. is this right analysis ? I mean
> is it possible to have B = zero and to have after cuts only the signal events ? according to the second and third SBratio the signal
> efficiency still finite ..
Well, that's your work. You should know which kind of events you generated. And then you should be able to conclude whether the fact of this cuts rejecting all events is correct.

Regards,

Benjamin

Revision history for this message
Benjamin Fuks (fuks) said : 		#3

Dear Safinaz,

> I read in the manual of MA that there are three formulas of SBratio : S/B, S/B+S, and S/sqr{S+B}. Where S and B are the number of the signal events and bkg events respectively . May I ask how to determine which formula should I use in my analysis ?
The treatment of this has changed in the last version of the code. Please have a look here:
   http://madanalysis.irmp.ucl.ac.be/raw-attachment/wiki/WikiStart/MA5%20v1.4.pdf

> Also I was studying some signal have energetic final states, and when I made cut on the transverse energy to reject events almost less than 200 GeV (besides other cuts on the mass ranges), all the Bkg events became zero .. is this right analysis ? I mean is it possible to have B = zero and to have after cuts only the signal events ? according to the second and third SBratio the signal efficiency still finite ..
Well, that's your work. You should know which kind of events you generated. And then you should be able to conclude whether the fact of this cuts rejecting all events is correct.

Regards,

Benjamin

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