However, the Standard Model is an incomplete theory because it still can't
fully explain the nature of the world.
Why are there three generations of quarks and leptons?
Are quarks and leptons really fundamental, or are they in turn made
up of even more fundamental particles?
Why can't the Standard Model predict a particle's mass?
According to our experiments, there should be equal amounts of
matter and antimatter in the universe; but, why have we observed the
Universe to be mostly made of matter?
How will gravity fit into the Standard Model?
We know that there must be a lot more matter in the Universe than we can
observe. What is this invisible dark matter?
Questions such as these drive particle physicists to build and operate newer and better accelerators, so that higher-energy collisions can provide clues to their answers.