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In this issue:
People: Harold Hwang Excels with Interfaces
The Search for Stopped Gluinos

SLAC Today

Wednesday - October 6, 2010

People: Harold Hwang Excels with Interfaces

Harold Hwang. (Photo courtesy Harold Hwang.)

Basic research into the properties of materials seems to cover a variety of highly technical subjects, such as high-temperature superconductivity, quantum effects, spintronics and catalytic behaviors, for example. Actually, all these areas of research boil down to one thing: control. Control of electron interactions. Control of materials synthesis. Control of emergent properties, or what happens when two very complex materials meet. The Office of Basic Energy Sciences, a part of the Department of Energy that supports fundamental research, has even identified five "grand challenges" for basic energy sciences that will lead, according to a BES report, to a "science of control."

Harold Hwang of the Stanford Institute of Materials and Energy Sciences, a joint SLAC-Stanford institute, may not be master of matter—yet—but he's learning to be very persuasive. Hwang researches "complex oxides"— materials that share similar crystal structures, but exhibit a broad range of properties. Complex oxides can act as insulators, semiconductors, metals and superconductors, to name only a few possibilities. Hwang and his group focus on fabricating crystals from extremely thin layers of these oxides, in the hopes that the crystals can be persuaded to retain the properties of the individual oxides. Either that, or new properties will arise due to interactions between the oxide layers.  Read more...

(Image - simulated ATLAS data)
Simulated stopping positions of gluino R-hadrons within ATLAS. (Image: ATLAS e-News.)

The Search for Stopped Gluinos

While most ATLAS physics analyses entail picking apart collision events and looking for the characteristic signatures of items of interest, a small team from SLAC has other ideas. The signal they're seeking is that of a "stopped gluino," and the best place to find evidence of it, they say, is not amongst the clamour of collisions but in the relative peace of empty bunch crossings.

Over the summer, the group used early ATLAS data to investigate the search backgrounds for these mysterious particles, and performed their own simulations to perfect methods for honing in on them, should they exist. Their findings were presented at the ICHEP meeting in Paris and SUSY10 in Bonn.

The gluino, supersymmetric partner to the gluon, features in all supersymmetry extensions to the Standard Model. Theory on the lifetime of this postulated particle varies, but the SLAC team is on the trail of a long-lived version; one which would be stable enough to travel the length of the detector before decaying. That is, unless it was stopped en route

"The way [the gluino] interacts means that it can become charged, so it loses energy through ionisation as it passes through the detector," explained SLAC ATLAS researcher Paul Jackson. "What can happen is it can lose all of its energy, run out of steam, and basically get caught in the detector."   Read more from ATLAS e-News...


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