What really happened?
In the previous chapter we identified all the particles produced in the detector. Now comes the more challenging question: what happened after the electron positron interaction? Summing up all the energies of the particles gives about 10 GeV. The center of mass energy of the colliding electron and positron is about 200 GeV. The most probable explanation of what happened is the following:
An electron and a positron did not annihilate, but passed each other. They scattered, each one sending out a photon. These photons annihilated and produced a quark-antiquark state. The mass of this state should not exceed the totally measured energy of the five particles, which come out of the collision point.
The standard model says that there are six different flavors of quark: with : up, down, charm, strange, bottom and top. Each one has an antiquark. Look up the masses of these quarks and find out which quark-antiquark states could have been produced. The flavor of the quark and the antiquark will be the same!
Click here for solution of exercise 4
Why are these detectors so huge?
Back to calculating the momentum and energy from the track radius