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Counting B Particles
Wednesday Lunchtime Jams
How the Mighty Fell

SLAC Today

Monday - July 24, 2006

(Photo - Counting B's)
Counting B's

Counting B Particles

How many B mesons does the B-factory make?

The BaBar detector has measured about 760 million of them so far. We know this because Chris Hearty of the University of British Columbia counts them.

The number matters to nearly all of BaBar's physics results. Most analyses work with a total number of events. The published result tells what fraction of particles decayed in a specific way. Some decays are common, some exceedingly rare.

To come up with his number, Hearty actually counts the overall number of Upsilon 4S events, each one made from a b quark and an anti-b quark. It decays into two B mesons, which in turn fall apart in hundreds of different ways that are examined by the BaBar collaboration. Papers usually quote the number of Upsilon 4S events—about 380 million to date.  Read more...

Weekly Lunchtime Jams

(Photo - Lunchtime Jam) From left to right, Joe Vargas, Aaron Jensen, Karen Holtemann and Chris Nantista. (Click to see larger version.)

Five musicians showed up for SLAC's inaugural lunchtime jam last Wednesday. With two six-strings, an acoustic bass, and improvised drums, the nascent group played its way through 1960s R&B to 1980s rock.

"In my workgroup here, we have a ton of musicians," says safety officer Karen Holtemann, who organized the session. "We've all kind of talked about getting together regularly. I thought I'd try it to see what would happen."

Physicists and mechanical experts joined Holtemann at the picnic tables between Buildings 24 and 25 and took to the songs quickly. The hum of nearby machinery competed with the music, but Holtemann is considering bringing an amp and moving to an indoor space. "It would be nice to go somewhere where we could make some noise," she says.

Holtemann plans to make the Wednesday session a weekly event. "If you come back in a month we'll sound like actual musicians," she said.

The group plans to meet again this Wednesday at 11:45 a.m. between Buildings 24 and 25. Both musicians and listeners are welcome to join. "Don't be shy, come sing with us," says guitarist Joe Vargas.

How the Mighty Fell

(Image - Fallen Oak)
This oak tree, located in the Sector 6 picnic area, lost two limbs in last week's heat and will have to be removed. (Click on image for larger version.)

Two limbs fell from the large oak tree in the middle of the Sector 6 picnic area last week, damaging two picnic tables. Facilities coordinator Carlos Pereira says the recreation area will be closed until the tree is cut down and the tables repaired. The area will likely reopen Monday, July 31.

The limbs fell sometime between Wednesday afternoon and Thursday morning, Pereira says.

Arborist James Lascot inspected the tree and concluded the limb cracked due to "sudden limb drop," which occurs when hot weather, combined with a lack of wind to carry moisture from the foliage, causes water pressure to build in the tree.

The oak, which Lascot estimated to be 250 to 300 years old, had already had a branch fall earlier this year.

Pereira says the current plan is to keep the tree stump at the picnic area as a tabletop. The rest of the tree will be cut into firewood and made available to SLAC employees.

Other outdoor eating areas remain available while the site is closed, including the picnic tables between Buildings 24 and 25, Building 40, Building 48 (the Research Office Building) and at the cafeteria.

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