Ground breaking news, people!
WOW!!! I don't remember if I ever enjoyed reading a news article word for word all the way, but in the end I'm left totally clueless about the subject matter.
I think its author definitely deserves some kind of award. Enjoy! 
But protons are bags of smaller particles called quarks and gluons, and their collisions tend to be messy and wasteful. Because electrons and positrons have no innards, their collisions are cleaner, so they can be used to create and study with precision whatever new particles are found at CERN.