How to Use CERN ROOT Tools for Global Fit with Multiple TH1D Objects?

Hello everyone,

I am currently engaged in data analysis for a specific reaction channel, where I need to determind the branch ratio of each channel. I have simulated possible process data using GEANT4. For this moment, there are three physical values and each save as histogram(TH1D*). Simularly, for each simulated process, same physical value exits and also save as TH1D*.

My goal is to make global fitting for the experimental data using those simulated data. Additionly, I am to evaluate the ratios that minimize the chi2.

One close code would be found at combinedFit_8C.(new user could no post link)
But there are some differents.

Thank you in advance and best regards,
Tianzhu Mo

Hi,

Thanks for the post and welcome to the ROOT Community!
I think the example you mention could bring you very far: don’t you just need to adapt the code to your histograms and extend the global fit from two histograms to three?

Cheers,
Danilo

Hi Danilo,

In the example I mentioned, the math function is used as follows:

 TF1 *fB = new TF1("fB", "expo", 0, 100);

and

   TF1 *fSB = new TF1("fSB", "expo + gaus(2)", 0, 100);

However, in my analysis, I required a different way. In this case,my fit funtion should be base on different histogram distribution like:ah1+bh2+ch3.Here, h stands for histogram data rather than mathematical experession. Shard paramater are a,b and c.This is the most biggest different.

Best Regards,
Tianzhu Mo

ROOT Forum → Search → TFractionFitter

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