I want to fit the data precisely

Hi Dear Experts…!!
I am working on RooFit to fit the data of di-muon invariant maas distribution. I’m trying to separate the signal from the background by fitting the sideband regions. I used two guassians pdfs for the signal region with mean, m= 91 and (sigma1, sigma2) = ( 1.5, 2.0) and a cheybechev polynomial for the sideband region with (a0, a1) = 0.5, 0.6) I’ve chosen the number of signal events as (5000, 0, 1000000) and that of the background as (3000, 0, 100000). And I get the fit as

You have probably to choose better initial parameter values. I don’t see sigma1 and sigma2 as fit parameters. If are fixed to 1.5 and 2.0 probably those are not good values for your data


HistoSum_Zroofit.C (4.8 KB)
Hi Dear Lorenzo, here is the file for the fitting.
thanks for your reply

i’ve tried different values of a0 and a1, ut no one seems to be suitable

I see that sigma1 and sigma2 are fixed, these values are probably not correct. Try to change or make them as fit parameters.
For running your code I would need to have your root file


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thankyou dear Moneta…The problem has resolved

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