Calculate the Top Quark MassStudents use conservation laws and vector addition to calculate the top mass from event displays. Students use momentum conservation, energy conservation and two-dimensional vector addition to calculate the mass of the heaviest of the six known quarks. They gather data from data plots from the DØ experiment at Fermilab. The events were chosen carefully; all of the decay products moved in a plane perpendicular to the beam. This makes the vector addition much simpler. Image Credit: DZero, Liz Quigg