Problem In Minuit

HI all
   I was trying to minimize a user define function by using Miniut in root. But i am facing problem that after a few iterations me parameter become nan and then same with calculated value of function. To avoid this i put a condition on function that return value when function is not equal to nan by doing this function is showing some junk values and chi2 become inf. Can some one tell me but is problem. I have attached header files main function file and data file. You can run it and see the problem.  Thankx     

Varinderjit Singh
Research Scholar
Dept. of Physics
Panjab University
Chandigarh
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