The Questions
While some of us might quibble about the details, most high energy physicists would agree that among the most important questions are the following:
Mass
"What is mass" is a complicated question with at least 4 different interpretations. It is as old as the concept's inventor, Isaac Newton. (Want to know more?)
"CP Violation"
Why are we people and not antipeople? Why do we live on Earth and not antiEarth? That every particle has as an evil twin an antiparticle is now an everyday technology. Even, a commodity. At Fermilab we deal with both Protons and Antiprotons. At some hospitals, you'll perhaps part of your body will be scanned by induced Antielectrons, or Positrons. But, we're dominated by particles, and not antiparticles. So...why? How did Particles win and Antiparticles lose in the evolution of the Universe? (Want to know more?)
Unification
Just as magnetism was united with electricity by James Clerk Maxwell in the 1860's into a common mathematical model called Electromagnetism, it and the so-called nuclear Weak Force were unified in the late 1960's into the Electroweak model...we have a belief - a dream - that the other fundamental forces, Gravity and the Strong (nuclear) force will be found to be fundamentally the same and described by a more general model. This is the source of the infamous Theory of Everything which is sometimes discussed - a hope for reducing the complexity of Everything into an all-encompassing description out of which all of the fundamental strengths can be composed. (Want to know more?)
Current and Anticipated Accelerators and Experiments
Experiments with Protons
Protons have long been used as particle beams because they are relatively easy to produce and guide in magnetic racetracks and straightaways. A modest bottle of hydrogen gas and service an entire government laboratory!
current
There are two laboratories in the world that use protons as beams. Fermilab collides protons with antiprotons in a large ring in central Illinois. The German (DESY) collides protons with electrons under the northern German city of Hamburg.
Anticipated
By 2007, the European Center for Nuclear Research (CERN) will have completed the construction of a huge accelerator of protons (actually, two accelerators, one for each of oppositely directed proton beams). This facility straddles the French-Swiss border under that Ural Mountain range near Geneva, Switzerland
Experiments with Neutrinos
The elusive neutrino - it would require light-years of lead to reliably stop a few neutrinos - has been a beam of choice for experiments since the 1950's. Luckily, even though they are notoriously shy, when they are in groups of, say 100,000,000,000 they make their presence known. Further luckily, beams with these sorts of numbers can be readily made. While their interactions themselves were the focus of decades of research, the elusive neutrino has become an object of study in and of itself. Previously thought to be massless - a weak form of light - recent discoveries in Japan have convinced physicists that they have a tiny, tiny mass. Just like electrons, neutrinos come in different kinds...certainly distinguished by different masses. It is the study of the different kinds of neutrinos and the weird quantum effects that mass differences can have on their actual identities, that occupies the most attention.
current
There are a variety of experiments currently under way. They come from three sources: nuclear reactors, the sky, and accelerators.
Anticipated
Fermilab is a few years away from the construction of a unique beam of neutrinos. The mass effects are most pronounced over long distances, where the neutrinos have the time to make their weird transformation definitively. Long distances. Like hundreds of miles long. Also, their study is sometimes dominated by extraneous particles, either tagging along in the beam itself or confusing measurements as unwanted cosmic rays. The way to get rid of the latter is go under ground. The way to definitively eliminate the former and get the long distance? Shoot the beam into the ground, which is just what Fermilab is doing: from the plains of Illinois, a beam of neutrinos will be sent to a detector in a mine near the Canadian border in the northern part of Minnesota!
Experiments with Electrons
current
Anticipated
The Elementary Particle-Astrophysics Connection
Looking Up at the stars and Looking In to the tiniest bits of matter are nicely complementary: Astrophysics and Elementary Particle Physics are intimately connected disciplines, each helping and constraining and motivating the other. (Want to know more?)