Physics Researchers Find Striking Quantum Spin Behavior

Scientists sometimes want to orient particles’ spins in a single direction in order to study the effect of spin on the scattering process, which in turn reveals a sort of medical scan of the particles' interior. The boson research was started at Indiana University's 0.5 GeV Cooler Storage Ring and continued at the Research Center Julich's 3 GeV COSY Storage Ring in Germany.

The team used beams of heavy hydrogen nuclei called deuterons. Because their spin value is exactly twice that of the more familiar elementary particles called protons and electrons, the deuterons are called bosons.

The behavior of spinning bosons is different from that of spinning electrons and protons, which can be fully described by their vector polarization. Describing spinning bosons also requires a tensor polarization which has one more dimension than a vector polarization, just as a sheet of paper has one more dimension than a string.

A speculative, but perhaps possible, application of this research comes from the spinning bosons’ extra dimension. This might make the still-speculative but promising quantum computers more effective, because much more information could be stored in the extra dimension—a lake can hold much more water than a narrow stream, said Alan Krisch, U-M physics professor.

However, the main result of this basic research is the demonstration of yet another phenomenon that can only be explained by the elegant but hard-to-believe theory called quantum mechanics, and by the still-mysterious quantity called spin, which apparently can only have values of exactly one, two, three or four times the electron’s and proton’s exactly equal single-spin-values, Krisch said.

The new COSY data will be presented at the May meeting of the American Physical Society in Denver in a preliminary report prepared by graduate student Vasily Morozov and Krisch, who led the team of researchers from U-M, Illinois Tech, and Bonn University and the Research Center Julich in Germany. Most of the team are now carrying out yet another spin experiment at COSY; its timing conflicts with the May 1-4, 2004 APS meeting in Denver; thus, U-M graduate student Charles Peters will present the data.

The striking behavior was first seen at the Indiana Cooler Ring in 2002, but publication was delayed because the behavior could not be explained by any known formula. Then in late 2003, soon after a Michigan seminar by Wisconsin professor and deuteron expert, Willy Haeberli, the team derived a formula, from the quantum mechanics for bosons, which exactly explained the behavior. The paper was then quickly published in Physical Review Letters in November 2003. In December, the experiment was repeated at the COSY Storage Ring; this higher energy experiment confirmed the striking behavior found at the Indiana Cooler Ring, as will be reported at the Denver APS meeting.

Krisch directs Michigan's Spin Physics Center, which has been studying the violent elastic collisions of spinning protons since 1970. For more on Krisch, visit:

http://www.physics.lsa.umich.edu/department/directory/bio.asp?ID=178