Beamguides and BaBar: A Visit to SLAC

Sunday, April 18, 1999: I took up an offer from my friend John Bartelt, who's a researcher at the Stanford Linear Accelerator Center, to visit the site before they turned on the beam for the BaBar experiment and we wouldn't be able to get a close look at the setup. This is big science, and the results will help answer a basic question: how come the universe didn't anilhalate itself?

Update: Saturday, July 7, 2001: The BaBar experiment reports its first major results. The paper Observation of CP violation in the B0 meson system was sent to Physical Review Letters on July 5, 2001.

John Bartelt and the Main Experiment Areas This is John on a hill overlooking the 'switchyard' some of the experiment areas of the accelerator. The accelerator portion extends two miles into the foothills of the Santa Cruz Mountains in the distance. The switchyard is used to steer the beam of high energy electrons into various experiments.

Experiment is an understatement. The experiment John's working on, BaBar, has 600 people from the US, England, France, and Japan working on it. The first few pages of any research paper published would just be the list of authors.

SLAC's Web site (the first Web server in the US) has a schematic of the site and will do a better job of explaining how these things work.

John Bartelt and the Main Experiment Areas This is inside the two mile-long accelerator. The beam of electrons and positrons (anti-electrons) runs underground. In this long shed are the power supplies for the beam and microwave sources used in controlling it. It's loud in this area, there are hundreds of transformers humming in an enclosed space.

BaBar

BaBar is a 'B factory.' It's designed to generate large numbers of a type of particle called a 'B meson.' These are needed to test a question of cosmology: since the universe is fond of symmetry, how come the Big Bang didn't produce equal amounts of matter and antimatter which would had anhilated each other? Or why is the universe biased towards matter, rather than antimatter?

The BaBar team recommends an article in New Scientist for more on this question.

BaBar apparatus, view of the decay detectors This is the BaBar detector. The concrete and iron shielding which will protect it from the magnetic forces steering protons and positrons into its maw are rolled away so people can work on it. I would had taken a picture with someone working inside it, but I didn't think they'd want their butt put on the Internet. The wires lead from 30,000 detectors which will look for B meson decay events and send them to a room full of Sun ULTRA 5s which will process the data.

The other side of the detector. BaBar detector with beam guides

SLAC's own page on BaBar describes the experiment in relation to the rest of SLAC.

Photos by Whump. Any errors in fact are his too.