TMinuit is not working

_ROOT Version: 6.14
_Platform:Mac OSX
Compiler: Not Provided

Hi all,

I am trying to do a chi-square minimization using TMinuit for 2 parameters. But I am continuously getting incorrect value of my FCN (chi^2) which is way off from the expected value. Also, I am keep on getting an error warning in HESSE that my error matrix is not POS-DEF. (I know this might be because of the fact that my parameters are correlated but I have checked it so many times and they are not correlated to each other). Since it’s just two parameters, I tried to write a small minimization routine of my own to see if there is some problem in my function but my minimization routine is working just fine with the same function that I am using in TMinuit. The reason for using TMinuit is because eventually I want to use 4 fit parameters on the same function and my minimization routine would be very inefficient.

The source code is in this file: min_min.C (4.0 KB)
The Output log is in this file: output.txt (2.3 KB)
Thanks in advance.

I’m not so sure, but to have the right chi-square value you should multiply the FCN value by 2.
Maybe people more expert than me can confirm this statement.


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