Recovery of radiated energy in the $B_d \to J/\psi(e^+e^-)K_S$ decay channel

B_d->J/\psi K_S is the golden channel to measure the unitary triangle angle beta. In the current LHCb off-line selection of the decay channel B_d -> J/\psi(e^+e^-)K_S, the reconstructed J/\psi mass peak and the B_d mass peak (to a lesser extent) are shifted to lower values due to the loss of energy by electrons and positrons, that cannot be reconstructed. This energy comes from non-reconstructed Bremsstrahlung and low energy radiated photons that have been emited before the electron or positron arrives to the magnet, where the track momentum is measured. In this note a method is presented to recover this energy after studying its probability distribution function.