histogram subtraction and mean

From: Margar Simonyan <margar.simonyan_at_gmail.com>
Date: Tue, 1 Mar 2011 12:37:36 +0100

Hello ROOTTalk

I get strange results after histogram subtraction, the attached script written in Python demonstrates the issue. My goal is to subtract background from signal+background distribution and get meaningful results for mean.
There are several unexpected (for me) results: First, the mean changes after subtracting empty histogram, this is not a big issue. Second, after subtracting background I don't get exactly the signal value. Third, rebinning before subtracting changes the results once more.
Can somebody explain this? I am using ROOT 5.26/00e complied on SLC5 with gcc43.

 Thanks,
       Margar

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  Dr Margar Simonyan,  post-doctoral researcher   Niels Bohr Institute, Copenhagen University

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Received on Tue Mar 01 2011 - 12:38:37 CET