double Event::MT(const ParticlePointer particle, const METPointer met) { double energySquared = pow(particle->et() + met->et(), 2); double momentumSquared = pow(particle->px() + met->px(), 2) + pow(particle->py() + met->py(), 2); double MTSquared = energySquared - momentumSquared; if (MTSquared > 0) return sqrt(MTSquared); else return -1; }