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In this issue:
LHC Countdown
Science Today: Dark Matter Illuminated
New SLAC Cell Phone Policy Implementation
Retirement Celebration for Lee Lyon
SSRL Celebrates Another Successful Run

SLAC Today

Thursday - August 28, 2008

LHC Countdown

The first beam on September 10 is possible due to the success of the August 26 LHC beam synchronization systems test (above). (Image courtesy of CERN. Click for larger image.)

Excitement is building for the September 10 startup of the Large Hadron Collider. Many SLACers are spending the next few weeks at CERN, helping with final preparations and basking in the anticipation. They describe a positive tension in the air that wasn't there a year ago: the beams are coming, and everyone can feel it.

The SLAC ATLAS (A Toroidal LHC ApparatuS) team is looking forward to being on-hand when the beam first goes through the ATLAS detector. "At this point there's very little we can do about it one way or another, but we're like parents waiting to see our kid's first step," said Charlie Young, who leads the SLAC ATLAS team in collaboration with Su Dong.

CERN will webcast the event beginning at 11:30 p.m. PDT on September 9. Photographs of the day's events will also be posted at regular intervals to the CERN LHC First Beam Web site. For even quicker updates, subscribe to the CERN Twitter feed.

(Daily Column - Science Today)

Dark Matter Illuminated

A new study confirms clear evidence of dark matter (blue), separated from ordinary matter (red) by a merger of galactic subclusters. (Photo courtesy of Maruša Bradač. Click for larger image.)

A new study of an immense cosmic collision has provided confirming evidence for dark matter. Our team analyzed the mass content of the enormous, merging galaxy cluster MACSJ0025.4-1222 using the Hubble and Chandra Space Telescopes to disentangle dark and normal matter—that is, matter made up of baryons, common subatomic particles such as protons and neutrons. The new results confirm those obtained from the 2006 study of the Bullet Cluster, providing a clear view of dark matter, separated from ordinary baryons.

The study examines the aftermath of a merger between two giant sub-clusters, each a whopping million billion times the mass of the sun. As these collided at millions of miles per hour, most of the normal, baryonic matter in each—in the form of hot, X-ray emitting gas—interacted with the similar matter in the other and slowed down, like a diver encountering the water's surface. In contrast, the dark matter did not interact significantly and passed through without disruption. This difference caused the dark matter to sail ahead, leaving the X-ray luminous, baryonic matter lagging behind.

We used high-resolution optical images from Hubble to infer the distribution of total mass through a phenomenon known as gravitational lensing, in which the otherwise invisible dark matter bends light from galaxies in the background. We used Chandra's high-resolution X-ray images to map the position of the baryons. The observations show a clear separation between the dark and X-ray luminous, baryonic matter, providing direct evidence for dark matter and supporting the view that dark matter particles interact only very weakly, through gravity but little else.

For a closer look:

See animations of a cluster collision from the Chandra Web site (QuickTime or MPEG) and from SLAC (.mov file).

Read the news release from HubbleSite News Center.

New SLAC Cell Phone Policy Implementation

Reminder: As all holders of SLAC cell phones have been informed, service will terminate on September 1. To help with the transition, here are SLAC's cell phone policy and technical information.

Retirement Celebration for Lee Lyon

(Photo - Lee Lyon)
Human Resources Director Lee Lyon.

Join Human Resources in the Research Office Building from 2:30 to 4:30 p.m. today to congratulate SLAC HR Director Lee Lyon on his retirement. This is a great chance to thank Lee for all he's done in 20 years of SLAC service. See the flyer for details and RSVP contacts.

Here's to you, Lee!

SSRL Celebrates Another Successful Run

(Photo courtesy of Hector Prado. Click for larger image.)

For about 30 years, staff at the Stanford Synchrotron Radiation Laboratory have held an annual party to celebrate the end of the user run. (Users generally conduct experiments at SSRL November through August.)

This year, about 200 people from SSRL joined with colleagues from the Linac Coherent Light Source and Photon Sciences Directorates and their families for a party at Mitchell Park in Palo Alto. Ben Poling and friends prepared a delicious barbecue dinner. People talked, laughed, met each others' families and pets, played volleyball, practiced their golf chipping skills and generally relaxed and had a good time.

As SSRL Director, I would like to thank the event organizers and acknowledge the dedication and hard work of the SSRL staff, and thank their families for their support.

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