The Case of the Hidden Neutrino
Students use momentum conservation to examine the decay of top-antitop pairs to determine what is missing from the event.
They examine 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. The net momentum of the top-antitop pair should be zero in the transverse plane. When it is not, this implies an equal and opposite "missing momentum" to balance that net transverse momentum. One interpretation is that an unseen particle carries this missing momentum.
This version of the “Top Quark Activity” has been redesigned to introduce neutrino physics or prepare students for a neutrino masterclass.