mother_probability.cc

#include "mother_probability.hh"
#include <cmath>

double mother_probability(stab::PseudoJet const &pij, stab::PseudoJet const &pjj,
                          const AlphaStrong &alphaS) 
{

   const FourVector pi(pij.e(),geom3::Vector3(pij.px(),pij.py(),pij.pz()));
   const FourVector pj(pjj.e(),geom3::Vector3(pjj.pz(),pjj.py(),pjj.pz()));
   const FourVector &pmo = pi + pj;

   const double pTi = pi.pt();
   const double pTj = pj.pt();

   const FourVector &phard = ( pTi > pTj) ? pi : pj ;
   const FourVector &psoft = ( pTj > pTi) ? pi : pj ;
   const double pTsoft = pTj > pTi ? pTi : pTj;

   return QCD_CA * 4.0 * M_PI * alphaS.alphaS( pTsoft*pTsoft ) * 
      pmo.dot(phard) / ( pmo.dot(psoft) * phard.dot(psoft) );

}