GenFilters/plugins/MCFilterZboostHelper.cc

0001 #include "GeneratorInterface/GenFilters/plugins/MCFilterZboostHelper.h"
0002
0003 #include <cmath>
0004
0005 HepMC::FourVector MCFilterZboostHelper::zboost(const HepMC::FourVector& mom, double betaBoost) {
0006   //Boost this Lorentz vector (from TLorentzVector::Boost)
0007   double b2 = betaBoost * betaBoost;
0008   double gamma = 1.0 / std::sqrt(1.0 - b2);
0009   double bp = betaBoost * mom.pz();
0010   double gamma2 = b2 > 0 ? (gamma - 1.0) / b2 : 0.0;
0011
0012   return HepMC::FourVector(
0013       mom.px(), mom.py(), mom.pz() + gamma2 * bp * betaBoost + gamma * betaBoost * mom.e(), gamma * (mom.e() + bp));
0014 }