Experimental Facilities: BaBar Detector

BaBar stands for B and B-Bar (written ).

• A B is a particle made from a d-quark and an anti b-quark ().
• Its antiparticle, , is made from an anti d-quark and a b quark ().

The B Factory produces millions of pairs of B and particles.

The BaBar detector (see image at right) records the particles produced when the B and the particles decay. There are many possible sets of decay products. However, the interesting decays for this experiment are quite rare -- on the order of one in a 1000 to one in 100,000. So, to see the interesting decays, we need to produce many B's. This detector uses a typical set of detector sub-systems to: Precisely measure the collision point and decay points of the B meson pairs produced. Precisely measure the momentum and energy of the decay particles. Determine the nature of the kind of particles in these decays (i.e. electrons, muons, pions, kaons).

Cutaway view of the BaBar detector.

Cutaway view Silicon Vertex Tracker for the BaBar detector

We are looking for differences in the likelihood of certain decay products coming from a B compared to the likelihood of the antiparticles of those products coming from a . The goal is to use these differences to decipher the tiny differences in the laws of physics for antimatter compared to the laws for matter.

The eventual hope is that this will help us understand how it happens that the Universe contains matter but very little antimatter. It is thought likely that in the first moments after the big bang there were equal amounts of matter and antimatter produced. If they had stayed equal, then the Universe today would be very uninteresting because all the matter and antimatter would have disappeared by the process:

matter + matching antimatterradiation

so no galaxies, no stars, no planets, and no people would be around today!

For current BaBar information, check out their public web site and the many SLAC press releases related to BaBar and the B Factory (below).

• September 28, 2006 - New Form of CP Violation Discovered
• June 22, 2006 : Physicists Size Up the 'Unitarity Triangle'
• July 1, 2005: BaBar Finds New Massive Particle
• August 2, 2004 : Physicists discover dramatic difference in behavior of matter versus antimatter
• July 21, 2004: SLAC experiment triples its data production for study of matter and antimatter
• April 28, 2003 : SLAC experiment identifies new subatomic particle
• July 23, 2002 : From Theory to Certainty. BaBar announces new result on Charge Parity violation
• April 12, 2002 : World's Largest Database reaches 500,000 Gigabytes
• July 26, 2001 : BaBar Physicists find a striking difference between matter and antimatter
• February 12, 2001 : Physicists publish first results from the B Factory at Stanford
• November 9, 2000 : SLAC's B Factory Achieves Design Goal
• October 26, 1998 : Energy Secretary Bill Richardson Dedicates New Research Facility at Stanford
• October 17, 2000 : SLAC wins Department of Energy award for project management
• May 28, 1999 : Physicists observe first events at Asymmetric B Factory (PDF)
• July 30, 1998 : B Factory Achieves First Collisions