# Calculating signal significances over backgrounds before and after cuts

Hi,
I am still quite new to ROOT. I don’t know if it is possible to calculate the signal significances before and after applying some cuts. If it’s possible can you give some basic ideas and/or references that I may look at to learn this?
It will be a great help to me.

Regards,
Saumyen

Hi and welcome!

Unfortunately your question is most likely not as simple as it sounds. If you perform a counting experiment, you can use the ROOT function here, which also supports an uncertainty on the background. You can read the details in the paper here. If you have a more complicated setup for your analysis, the book here is a good resource.

Best
Stefan

Thank you so much, Stefan, for the quick answer. And I am sorry for such a delay.
I will be using Delphes output files for the signal as well as the background. I looked at the references suggested by you. But I saw that I need PDFs. Now, how do I get the PDF of some histogram(s)? I mean is it possible?
So far what I was doing is using the metric “S/sqrt(S+B)”, with S and B are event number obtained by “cross-section * Luminosity” I was calculating the significance. I suppose this is wrong, right?
But from the references what I found is using a particular histogram the signal significance is being calculated. So what happens if I take different histograms of the same analysis?
I am sorry if this is a very disturbing question. I am new to this field so I don’t have that much understanding yet.

Thanks a lot again.

Regards,
Saumyen

Hi Saumyen,

In this forum, we discuss the technical aspects of ROOT, but unfortunately, we don’t have time to discuss topics that you can find in textbooks. I would recommend you contact supervisors/colleagues or look for nice textbooks on statistics.

Best
Stefan

Yes, I understand. I was, in fact, doubtful if I shold ask it here. I’m sorry!

Thanks anyway for the helps.

Regards,
Saumyen

This topic was automatically closed 14 days after the last reply. New replies are no longer allowed.