double initQCD(double MZalphaS, double McMc, double MbMb, double MtP)
{
double Mq,Mq_;
lambda[5]= findLambda(5,MZalphaS, 91.187);
MtPole=MtP;
if(MtP< poleQmass(91.187,MZalphaS, 6)) return -1;
for(Mq=MtP,Mq_=0;fabs(Mq_-Mq)>0.00001*Mq;)
{ double alpha=alpha3(Mq, lambda[5], 5);
Mq_=Mq;
Mq*=MtP/poleQmass(Mq, alpha, 6);
}
qMass[6]= Mq;
lambda[6]= findLambda(6,alpha3(qMass[6],lambda[5], 5),qMass[6]);
notInitialized=0;
qMass[5]=0; qMass[4]=0;
if(MbMb<=lambda[5]) { qMin=lambda[5]; return qMin;}
qMass[5]=MbMb;
MbPole=poleQmass(MbMb, alpha3(MbMb,lambda[5] ,5),5);
lambda[4]= findLambda(4,alpha3(qMass[5],lambda[5],5),qMass[5]);
if(McMc<=lambda[4]) {qMin=lambda[4]; return qMin;}
qMass[4]=McMc;
lambda[3]=findLambda(3,alpha3(qMass[4],lambda[4],4),qMass[4]);
qMin=lambda[3]; return qMin;
nfMax=6;
}
static double findLambda(int nf,double alpha, double M)
{ double l1=0.1, l2=0.3;
double l,a,a1,a2;
l2=M*exp(-2*M_PI/alpha/(11-2*nf/3.));
while((a2=alpha3(M,l2,nf)-alpha) < 0) l2*=1.2;
l1=l2*0.8;
while((a1=alpha3(M,l1,nf)-alpha) > 0) l1*=0.8;
do{ l=(l1*a2-l2*a1)/(a2-a1);
a=alpha3(M,l,nf)-alpha;
if(a<0) { a1=a;l1=l;} else {a2=a;l2=l;}
} while (fabs(a) > 0.00001*alpha);
return l;
}
double alphaQCD(double Q)
{
if(notInitialized) initQCD(0.1172,1.2,4.23,171.4);
if(Q<qMin) return 1; return alpha3(Q,lambda[NF(Q)],NF(Q));
}
double alphaQCD(double Q)
{
if(notInitialized) initQCD(0.1184,1.2,4.23,173.07);
if(Q<qLim) Q=qLim;
if(Q<qMin) return 1; return alpha3(Q,lambda[NF(Q)],NF(Q));
}
