The Vanderbilt QuarkNet program planned for the summer of 2003 will contain some of the same elements as the 2002 program. There are two complementary projects which address the main theme of QuarkNet, namely elementary particle physics.:

1. Measuring the Muon's Lifetime:In an Experiment With Cosmic Rays ... See also the Muon Detector Website.
2. Elementary Particles Produced in An Electron-Positron Collider Experiment (BaBar): Studies With an Event Display ...: See also the BaBar website for the public.

In addition to the above two activities related to elementary particle physics, various members of the physics and other science departments will discuss their research and offer tours of their lab facilities. The actual schedule for the summer 2003 may be obtained by clicking here.

The muon is an elementary particle very much like the electron, except that it is about 200 times as massive. Muons may be created on earth with particle accelerators, but we study muons that come from outer space in the form of cosmic rays. We use an apparatus to trap tens of thousands of cosmic ray muons and we measure the average time it takes for them to decay into lighter particles. The average time it takes for a muon to decay is only about one millionth of a second! This average time is also called the muon lifetime.

If you are a high school physics teacher or a high school student studying physics, you may already know about some of the things mentioned. Whether or not you know a very little, or happen to be somewhat knowledgable about elementary particles (congratulations if you are one of those), you should be asking questions like the following:

• Exactly what are cosmic rays from outer space? Where in space do they come from? How are they produced?
• What is an electron? What do electrons have to do with atoms, and what are atoms? What is the connection between atoms and elements, like hydrogen, oxygen, nitrogen, iron, etc.?
• In what ways are muons similar to electrons? In what ways are they different?
• Is a muon's lifetime like the lifetime of a person or an animal? In other words, are there old muons and young muons or are all muons the same? How can this be?

Before suggesting where you should look for answers to these and other questions, let's comment on our second project, that of studying "events" with BaBar event display. BaBar is the name of an experiment at the Stanford Linear Accelerator Center that involves physicists from all around the world, including Vanderbilt. The central purpose of the experiment is to study the so-called matter-antimatter puzzle. The puzzle is this: all evidence points to the fact that our universe was created in a "Big Bang" about 13 billion years ago with equal amounts of matter and antimatter, yet today's universe is populated only by matter. Where did the antimatter go? You may have heard about antimatter from Star Trek, and you think it is science fiction. Be assured that it is real! You will discover antimatter when you study the "events" created in the BaBar experiment.

BaBar is an experiment where both matter and antimatter are created, and the BaBar experiment (along with a similar experiment in Japan with the name Belle) is designed to study the ways that matter and antimatter behave differently, in the hope of understanding the matter-antimatter puzzle of the universe.

By the way, the name BaBar, besides being the name of the dapper elephant in the children's book, has something to do with what we study. The BaBar experiment recreates conditions of the early universe by colliding high energy electrons with high energy positrons (the antiparticle of the electron) to produce matter in the form of B mesons and antimatter in the form of anti-B mesons (also called B-bar mesons). Hence BaBar is a whimsical shorthand way of refering to B and B-bar.

You will learn that elementary particles are meant to be the most basic building blocks of nature, i.e., there is nothing smaller than elementary particles. Muons and electrons are elementary particles, but atoms are not elementary because they are made of electrons, protons and neutrons. Although electrons are elementary, protons and neutrons are not, because they are made of quarks, which are elementary particles ... as far as we know. B mesons are not elementary, as we shall see, because they too are made of quark-antiquark pairs.

You should now have many more questions. Let us suggest some questions for you to consider:

• Do the B mesons produced in the BaBar experiment have a lifetime like that of the muon? What is the lifetime of the B meson?
• What is the complete list of elementary particles?
• If elementary particles are very small, what do we know about their sizes?
• How does the BaBar experiment recreate conditions of the early universe?
• How do physicists study the properties of such small particles?
• What has been learned so far about the matter-antimatter puzzle from the BaBar and Belle experiments?

You should seek answers to the above questions, and all of your own questions, by studying some of the excellent resources available on elementary particle physics. In particular, see The Particle Advanture website linked from our home page. Also see the discussion about matter and antimatter, as well as comments about the BaBar and Belle experiments by clicking here. We also recommend the textbook by Barnett, Muhrey and Quinn titled The Charm of Strange Quarks. Copies will be available to all QuarkNet teachers. Also, see what we have posted about the muon lifetime and BaBar event studies for the summer 2002 session.