Reconstructed J/Psi mass peak from electron-positron pairs in the FMS

PYTHIA subprocesses:

• 86 g+g->J/Psi+g
• 87 g+g->chi_0c+g
• 88 g+g->chi_1c+g
• 89 g+g->chi_2c+g
  
• 106 g+g->J/Psi+gamma

Smearing from vertex and/or energy resolution (linear term) from toy simulation (Gaussian):
The width is determined from a fit to a Gaussian function.