SLAC Today is available online at:
http://today.slac.stanford.edu

In this issue:
SLAC and the Higgs
Twentieth Anniversary of First Z˚ and SSRL Angiography Advance
SLAC Public Lecture April 28: Black Holes, the Brightest Objects in the Universe

SLAC Today

Tuesday - April 14, 2009

SLAC and the Higgs

(Photo)
Evidence narrowing the likely values for the Higgs mass. The green bar on the far right represents the heavy mass range that the SLD results helped to exclude. (Image: Symmetry Breaking.)

In the 1990s the Stanford Linear Collider and Detector at SLAC produced and studied Z bosons, in tight competition with the Large Electron-Positron Collider, or LEP—the precursor to the Large Hadron Collider at CERN. LEP won out in terms of numbers, collecting about 12 million Z bosons to SLAC's 500,000. But what the SLD couldn't provide in numbers, it made up in technique. In the end, the competition was really a collaboration: the two experiments needed one another to form a complete picture of the Z boson and its properties.

More than ten years later, the work done by SLD and LEP on the Z boson is guiding the search for the Higgs boson at two of largest particle accelerators in the world. The Higgs determines certain properties of the Z boson, and SLD scientists used data on the Z to infer the mass of the Higgs. These indirect measurements done by SLD and LEP are inconsistent with a heavy Higgs, following the Standard Model of particle physics. In essence, this work frames the window in which Fermilab and CERN are now looking for the Higgs.

"The Z boson experiments set the stage for the current Higgs search," says SLAC theorist Michael Peskin, "and the data from SLAC provided some of the strongest constraints."  Read more...

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Twentieth Anniversary of First Z˚ and SSRL Angiography Advance

Saturday, April 11 marked the 20th anniversary of the first recording of a Z˚ particle by the Stanford Linear Collider. The feature article in the April 1989 issue of the SLAC employee newsletter, SLAC Beam Line, crowed, "The long wait is over," but Burton Richter's lab director's column in the same issue cautioned staff that the SLC still had a long road ahead of it. (See "SLAC and the Higgs," above for more on the Z boson.)

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It was 20 years ago this month, in that same issue of SLAC Beam Line, that the Stanford Synchrotron Radiation Laboratory announced a major advance in the imaging of human coronary arteries employing dual beams of synchrotron radiation produced in a dedicated run at the SPEAR storage ring.

Read the entire April 1989 issue of the SLAC Beam Line online.

SLAC Public Lecture April 28: Black Holes, the Brightest Objects in the Universe

On Tuesday, April 28, the SLAC Public Lecture series presents astrophysicist Jonathan McKinney of the Kavli Institute for Particle Astrophysics and Cosmology, with a presentation on the mysteries and contradictions of black holes.

Black holes are everywhere in the Universe. They form when massive stars end their life in a simultaneous violent collapse and energetic explosion. Galaxies end up littered with small black holes, each roughly the mass of ten Suns. Nearly every galaxy center ends up with a single huge black hole, with the mass of a million to a billion Suns. During their lifetimes, black holes chew up their surroundings and spew out ultra-energetic beams of radiation and matter that are visible from across the Universe. In this lecture, McKinney will discuss how black holes form, outline how we detect them, and show movies that illustrate how they work according to Einstein and state-of-the-art computer simulations. Come see that these blackest of all objects in the Universe actually shine the brightest.

McKinney's talk will take place 7:30-8:30 p.m. in Panofsky Auditorium, and is free and open to all.

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