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Probability ditribution of mass constraint fitting in oct14 vs. mar15
https://forum.gsi.de/index.phpindex.php?t=rview&goto=18355&th=4653#msg_18355
I simulated 2k evt of this decay chain:
pbarp->Ds+ Ds-; Ds- -> K+K-pi-; Ds+ -> eta e+ nu_e; eta -> pi+ pi- pi0; pi0->2 gamma.
Inorder to reconstruct eta, I do mass constraint fitting on (pi+, pi- pi0) after the vtx fitting of combined charged daughters. Recently I find the probability distribution of the eta mass constraint fitting seems incorrect, where most of prob are skewed to 1 and chi2 is very small, i.e. the mean value of chi2 is 0.0003. The interesting thing is this doesn't happen in the mass constraint fittings of Ds- (pure charged daughters) and pi0 (pure neutral daughters). This problem is found with the release mar15 (#27529). I test the identical code with release oct14 (#26514), and find this problem doesn't arise there (see attached histograms). The code I used for testing is attached.
Question: Why it happens and how can I fix it?
Many thanks in advance.
Best regards,
Lu
]]>Lu Cao2015-07-07T13:25:13-00:00Re: Probability ditribution of mass constraint fitting in oct14 vs. mar15
https://forum.gsi.de/index.phpindex.php?t=rview&goto=18361&th=4653#msg_18361
StefanoSpataro2015-07-08T08:47:13-00:00Re: Probability ditribution of mass constraint fitting in oct14 vs. mar15
https://forum.gsi.de/index.phpindex.php?t=rview&goto=18369&th=4653#msg_18369
Lu Cao2015-07-08T11:02:25-00:00