SLAC Today is available online at:
In this issue:
Which right neutrino is right?
Science Today: BaBar Data Acquisition
Stanford Jazz Concert
Save the Date

SLAC Today

Thursday - May 10, 2007

Which Right Neutrino is Right?

Michael Peskin's chalkboard diagram shows why neutrinos with mass cannot be only left-spinning. (Click on image for a close-up of the diagram and an explanation).

It's one of the mysteries of the universe: do neutrinos act as their own antiparticles? Force-carrying particles like photons do. Particles that don't carry force have separate antiparticles: the electron has the positron; the b quark has the anti-b quark, and so on.

What about the neutrino? Like electrons and quarks, it's a fermion. Yet, it might very well act as its own antiparticle. In this case, it is called a Majorana neutrino. Knowing whether Majorana neutrinos exist will shed light on how neutrinos get mass, what a right-handed neutrino looks like, and how the universe became dominated by matter. To answer these pressing questions, experiments such as the Stanford-led Enriched Xenon Observatory (EXO) plan to look for the phenomenon.

"It would be incredibly cool if fermions could be their own antiparticles," said SLAC theorist Michael Peskin.

(Daily Column - Science Today)

BaBar Data Acquisition

(Photo - BaBar Group)
Members of the BaBar online and data acquisition team. (Click image for larger version. Photo courtesy Diana Rogers.)

In the BaBar interaction region at PEP-II, bunches of electrons and positrons cross each other 250 million times per second. The "luminosity" of PEP-II is a measure of how often this produces electron–positron collisions. A fraction of these collisions leads to interesting physics, such as the production of B mesons, charmed particles, or tau leptons—in recent running, about 50 times per second. However, other types of interactions of the beams with each other or with the accelerator occur at a much higher rate, and many of these "background events" leave a detectable trace in the experiment.

PEP-II is now able to operate at four times its design luminosity, thanks to very dedicated efforts by many people at SLAC, and more improvements are expected. It is thus essential that BaBar be able to analyze the maximum possible fraction of the interesting interactions produced.

When the particles produced in a beam interaction enter the BaBar detector, its systems record their passage electronically, producing data that can be stored for further analysis. The detector hardware makes a decision about eight million times per second of whether an interaction has occurred that is interesting enough to merit further study. In recent BaBar running, the decision is "yes" 3,000 to 5,000 times per second. Each time, it is the responsibility of the detector's data acquisition system to take an electronic "snapshot" of the traces of the particles, amounting to about 35 kilobytes of data.


Stanford Jazz Concert

(Photo - Jamie Davis)
Jamie Davis, vocalist for the Count Basie Orchestra and former SLAC employee, will perform at the Stanford Jazz Orchestra Concert in Dinkelspiel Auditorium next Wednesday evening, May 16, at 8:00 p.m. Tickets cost $10. More information is available at the Stanford Jazz Orchestra website.

SLAC Softball Springs Eternal

(Photo - Softball)

The crack of the bat and the satisfying thump of a well-caught ball will soon sound on the SLAC Green again. Softball practice starts today at 5 p.m., and all are welcome to join. Players of all ability levels will practice on Thursdays this month on the Green, the grass lawn between the cafeteria and the A&E Building. Starting in June, play moves to Stanford campus, where the SLAC Spinors compete in the relaxed Intramural League once a week throughout the summer. For more information, contact coach Daniel Flath.

Save the Date: Cardinal Walk

Save the afternoon of May 31st for the first annual Stanford "Cardinal Walk" at Roble Field. Refreshments will be served beginning at 11:30 a.m. and free pedometers will go to the first 2,000 people registering at the event. The 1.5 mile walk, led by Provost John Etchemendy, will begin at 12:05 p.m. Questions can be directed to Jennifer Sexton.

Events (see all | submit)

Access (see all)

(see all | submit)

 Lab Announcements

Community Bulletin Board

News (see all | submit)

dividing line
(Office of Science/U.S. DOE Logo)

View online at