MadAnalysis 5

Uncertainties in event number

Asked by sengpei

After Madanalysis normalizes the number of events to the luminosity, the normalized number of events has an uncertainty attached to it. After applying cuts, there is also an uncertainty on the number of events that passes the cut. I wish to know where this uncertainty comes from, and could you tell me if there is any way to reduce this uncertainty?

Thanks!
Sengpei

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MadAnalysis 5 Edit question
Assignee:
Benjamin Fuks Edit question
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Benjamin Fuks
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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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sengpei (seng2pei) said : 		#2

Is it written in the manual or somewhere else? I would greatly appreciate your answer. Thanks!

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Benjamin Fuks (fuks) said : 		#3

Hi Sengpei,

The uncertainty is the statistical uncertainty associated with the number of events passing the cut. What do you mean by reducing it?

Cheers,

Benjamin

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sengpei (seng2pei) said : 		#4

Hi Benjamin,

I would like to determine the number of events that passes some cuts that I implement. I have tried to build my own program and applied the cuts (I have cross-checked my result with other people). Then, I tried to apply the same cut using Madanalysis5. The result Madanalysis5 gives me does not seem to be accurate (although it is within the uncertainty given by Madanalysis5). Is there anyway to improve the Madanalysis5?

Cheers,
Sengpei

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Best Benjamin Fuks (fuks) said : 		#5

Hi Sengpei,

I do not see what you want to improve? You have N1 events. You apply a given cut. You have N2 events. Whatever you use MadAnalysis 5 or your own code, if the cut is correctly implemented, you should get the same N2 number. Concerning the uncertainties, not that there is not a single way to calculate them. We are using binomial laws. What are you using? In any case, it is not a matter of being accurate but of estimating the uncertainties in a given way.

Does it clarify? Maybe should you give me a concrete example so that I could try to reproduce the issue.

Cheers,

Benjamin

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sengpei (seng2pei) said : 		#6

Thanks Benjamin Fuks, that solved my question.