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People: Sloan Fellowship Will Help Jacob Wacker Explore the Fundamentals

(Photo - Jacob Wacker)
SLAC theorist and Sloan Fellow Jacob Wacker. (Photo by Julie Karceski.)

Jacob Wacker is a newly-minted recipient of the Sloan Fellowship, an award aimed at supporting the research of promising scientists still early in their careers. As a specialist in theoretical high-energy physics, he is entering his fourth year as an Assistant Professor in Particle Physics and Astrophysics at SLAC. In his research, Wacker looks beyond the Standard Model, a set of laws governing matter and energy, to further explain the unknown in physics.

In the next year, Wacker expects the pace and scope of his research to accelerate with the commissioning of the Large Hadron Collider in Europe. He intends to use the fellowship funding to support graduate students and computing resources for him and his research team during this time.

In the convoluted world of theoretical physics, Wacker channels his energy into two rather different questions: the nature and origin of very long-lived particles and new theories of dark matter. Both of these research areas, while highly abstract, probe at the very fundamental properties of the particles and forces that make up our universe.

"We are explorers in some sense," he said. "With the LHC beginning to commission, this is the best chance at discovering new laws of nature."

With highly-sophisticated tools like the LHC and the Tevatron collider at Fermi National Accelerator Laboratory, Wacker and his colleagues can chip away at these large and abstract topics. He is looking forward to using the LHC to study gluinos, one of the hypothetical long-lived particles under investigation. Based on current theory, discovering the gluino would support a theoretical framework called supersymmetry, signifying to scientists that less than half of all fundamental particles in nature are known and ushering in a new era in high energy physics.

Gluinos are expected to have surprisingly long lifetimes. Produced in particle accelerators by smashing together two protons, they would become trapped in detectors and decay unpredictably in bright flashes of energy. Normally, particles created by high-energy collisions will exist for only a brief moment; but gluinos are predicted to last anywhere from a fraction of a second to years.

"Having very long-lived particles is very unusual," Wacker said. "We want to know why this particle has this long lifetime."

Wacker also would like to unravel some of the peculiar data relating to dark matter, a the substance believed to make up as much as 80% of mass in the universe. Detectable only through its gravitational pull on other objects, dark matter does not emit light, forcing scientists to pursue creative means of tracking it down.

"Numerous searches for dark matter have many anomalies in them," he said. "We want to confirm or refute these anomalies within the next year."

One such problem is with cosmic rays, which are particles accelerated to high energies in space. Their energy spectrum, or highs and lows in terms of speed and acceleration, is outside the range predicted by current theory. Some theories of dark matter predict that it could produce cosmic rays in the process of annihilating, or becoming totally destroyed. Scientists think it is possible that dark matter annihilation makes cosmic rays more energetic than expected.

Wacker offers ideas for new searches to experimental physicists and they in turn bring data to Wacker for a theoretical explanation. By resolving some of the quirks in their data sets, Wacker and colleagues hope to pool snippets about dark matter into a singular, sound theory that goes beyond the Standard Model of physics.

"There could be rapid advancements over the next six months to one year that will reshape how we see our place in the universe," he said.

—Julie Karceski
  SLAC Today, March 17, 2010