Int_t nparticles = fRunLoader->GetHeader()->GetNtrack();
printf("Number of Particles = %d \n", nparticles);
fRunLoader->GetEvent(ievt);
Int_t nparticles = fRunLoader->GetHeader()->GetNtrack();
printf("Number of Particles = %d \n", nparticles);
fRunLoader->GetEvent(ievt);