#include "TMath.h"
void reconstruct(Event * event) 
{
    float e=event->eTrue(); // get true energy
    float eReso=0.1*sqrt(e); // compute resolution
    float eSmeared=e+eReso*(gRandom->Rndm()-0.5); // smear with a flat distribution
    event->seteReco(eSmeared); // set the reconstructed energy
}