Modified Hagedorn Function in ROOT

double funModiHagedorn(double * x, double * par) {

    double scale = par[0];

    double a = par[1];

    double b = par[2];

    double p0= par[3];

    double n = par[4];

    double pt = TMath::Sqrt(x[0]*x[0] + par[5]*par[5] - 0.13957018*0.13957018);

    double dndy = scale * TMath::Power(TMath::Exp( (-1) * (a*pt + b*TMath::Power(pt,2)) ) + pt/p0, n*(-1));

    

    return dndy;

}

reference :
http://arxiv.org/abs/hep-ph/0602120
Modified Tsallis function: http://sympnp.org/proceedings/58/E21.pdf