I’m trying to fit a model curve to some data by performing a chi square minimisation wrt three parameters $ a,b$ and $ NN$ . The trouble I am having is that the variables with which I want to minimise the chi square with respect to appear in an integral. I attach the code I am working with.

Needs["ErrorBarPlots`"]  MasData5 = {{{44.8, 47.5}, ErrorBar[4.0]}, {{54.8, 50.1},  ErrorBar[4.2]}, {{64.8, 61.7}, ErrorBar[5.1]}, {{74.8, 64.8},  ErrorBar[5.5]}, {{84.9, 75}, ErrorBar[6.2]}, {{94.9, 81.2},  ErrorBar[6.7]}, {{104.9, 85.3}, ErrorBar[7.1]}, {{119.5, 94.5},  ErrorBar[7.5]}, {{144.1, 101.5}, ErrorBar[8.3]}, {{144.9, 101.9},  ErrorBar[10.9]}, {{162.5, 117.8},  ErrorBar[12.8]}, {{177.3, 130.2},  ErrorBar[13.4]}, {{194.8, 147.7},  ErrorBar[17.1]}, {{219.6, 137.4},  ErrorBar[20.1]}, {{244.8, 176.6},  ErrorBar[20.3]}, {{267.2, 178.7},  ErrorBar[21.1]}, {{292.3, 200.4}, ErrorBar[29.1]}, {{60, 55.8},  ErrorBar[4.838]}, {{80, 66.6}, ErrorBar[7.280]}, {{100, 73.4},  ErrorBar[6.426]}, {{120, 86.7}, ErrorBar[7.245]}, {{140, 104},  ErrorBar[12.083]}, {{160, 110}, ErrorBar[16.279]}, {{42.5, 43.8},  ErrorBar[3.482]}, {{55, 57.2}, ErrorBar[3.980]}, {{65, 62.5},  ErrorBar[4.614]}, {{75, 68.9}, ErrorBar[5.197]}, {{85, 72.1},  ErrorBar[5.523]}, {{100, 81.9}, ErrorBar[5.368]}, {{117.5, 95.7},  ErrorBar[6.277]}, {{132.5, 103.9}, ErrorBar[6.912]}, {{155, 115},  ErrorBar[7.920]}, {{185, 129.1}, ErrorBar[9.192]}, {{215, 141.7},  ErrorBar[10.666]}, {{245, 140.3}, ErrorBar[14.526]}, {{275, 189},  ErrorBar[24.274]}, {{49, 39.2}, ErrorBar[10]}, {{86, 75.7},  ErrorBar[14.414]}, {{167, 118}, ErrorBar[22.828]}, {{43.2, 50.7},  ErrorBar[1.5]}, {{50, 59.5}, ErrorBar[1.4]}, {{57.3, 61.8},  ErrorBar[1.9]}, {{65.3, 67.6}, ErrorBar[1.7]}, {{73.9, 72.4},  ErrorBar[1.9]}, {{83.2, 79.9}, ErrorBar[2.3]}, {{93.3, 84.4},  ErrorBar[2.1]}, {{104.3, 86.7}, ErrorBar[2.7]}, {{47.9, 55.4},  ErrorBar[2.1]}, {{68.4, 66.4}, ErrorBar[2.9]}}; (*this is the experimental data *)  gamma = 5.55*^-6; MJpsi = 3.1; alphaem = 1/137; alphas[k_] = 4*Pi/9/Log[k/lambda];  lambda = 0.09; Ca = 3; (*list of constants and k dependent function alphas*)  xg = NN*((4*qbar)/((4*qbar - MJpsi^2) + w^2))^(-a)*(qbar)^b*Exp[Sqrt[16*Ca/9*Log[(4*qbar - MJpsi^2 + w^2)/(4*qbar)]*  Log[Log[qbar/lambda]/Log[qo/lambda]]]] (* def xg, appearing in below *)  F5[w_] = 3.89379*^5*1/4.5/16*4*Pi^3*MJpsi^3* gamma/12/  alphaem*(Nintegrate[     alphas[k_]/qbar/(qbar + k_)*      D[(2^(2*(D[Log[xg],                  Log[1/(((4*qbar))/((4*qbar - MJpsi^2) +                  w^2))]]) + 3)/Sqrt[Pi]*          Gamma[D[Log[xg],               Log[1/(((4*qbar))/((4*qbar - MJpsi^2) + w^2))]] +              5/2]/ Gamma[            D[Log[xg],               Log[1/(((4*qbar))/((4*qbar - MJpsi^2) + w^2))]] +              4])*NN* (((4*qbar))/((4*qbar - MJpsi^2) +              w^2))^(-a)*(k_)^b*        Exp[Sqrt[          16*Ca/9*Log[(4*qbar - MJpsi^2 + w^2)/(4*qbar)]*           Log[Log[k_/lambda]/Log[qo/lambda]]]], k_], {k_,       qo, (w^2 - MJpsi^2)/4}] +     0.118/qbar/qo*Log[(qbar + qo)/qbar]*     NN* ((4*qbar)/((4*qbar - MJpsi^2) + w^2))^(-a)*(qo)^      b*(2^(2*(D[Log[xg],               Log[1/(((4*qbar))/((4*qbar - MJpsi^2) + w^2))]]) +            3)/Sqrt[Pi]*       Gamma[D[Log[xg],            Log[1/(((4*qbar))/((4*qbar - MJpsi^2) + w^2))]] + 5/2]/         Gamma[D[Log[xg],            Log[1/(((4*qbar))/((4*qbar - MJpsi^2) + w^2))]] +           4]))^2; /. { qbar -> 2.4025, qo -> 2} (*my model function - involves a numerical integration over variable k_ *)    chisq5 = Sum[((MasData5[[k]][[1]][[2]] - F5[MasData5[[k]][[1]][[1]]])/   MasData5[[k]][[2]][[1]])^2, {k, 1, Length[MasData5]}]; (*def of my chi square function *)    rr = Minimize[chisq5, {a, b, NN}] (*minimise chi square wrt a,b,NN *) 

This gives me an error that the output is not a number at {a,b,NN}. Can mathematica handle minimisation of a function wrt variables that are involved in an integration? I would have thought yes as the numerical integration involved is simply a nested operation but perhaps I have to adapt my syntax. Or perhaps the error is simply something else I overlooked? Thanks for any pointers.