Physics Colloquium, April 5, 2005

The Asymmetry Between Matter and Anti Matter - or - How to Know if it is Safe to Shake an Alien's Hand?

Klaus Honscheid

Department of Physics, The Ohio State University

Most of us have looked at the spectacular pictures taken by the Hubble Space Telescope. Galaxies, nebulae, super novae -- but there is something peculiar about these images. Where ever we look in space we only see matter. No significant quantities of anti-matter have been found. Since we believe equal amounts of matter and anti-matter have been produced originally we must conclude that there is an asymmetry between particle and anti-particle decays.

In the laboratory, however, nature always seems to obey the particle - antiparticle symmetry with one known exception. Almost 40 years ago a small difference has been found in the neutral kaon system. But the nature of this system made it extremely difficult for both theorists and experimentalists to extract a clear picture of this effect.

For years there has been great hope in the particle physics community that a large matter - antimatter asymmetry can be observed in a new system - the weak decays of massive B mesons.

The past decade has seen a vigorous experimental effort to produce the large quantities of B mesons required to discover the cause of this asymmetry. Particle accelerators have been upgraded and new detectors were constructed. As we enter the Golden Age of B physics nearly a billion B meson decays have been recorded by these experiments. I will review some of the old questions that have been answered and discuss some of the new puzzles that have been uncovered.

3.30 p.m., Smith Laboratory, Room 1005

Refreshments served in Atrium at 3:00 p.m., Physics Research Building