When a proton or other hadron (a bound state of quarks) is shot into a large nucleus, it is usually absorbed, as its quarks interact strongly with the quarks in the nucleus via their color fields. However, in some very special cases, the hadron can sail right through without interacting. The theory of quark interaction -- quantum chromodynamics, or QCD -- predicts that a hadron is a superposition of states with different sizes from large to small, with the small-sized components most important when the hadron is produced at high energies. In this state, all the quarks are practically sitting on top of each other, canceling each other's color fields. In this short-lived state, the hadron becomes temporarily invisible to the nuclear quarks and is thus able to escape the nucleus. This phenomenon is called color transparency "CT".

In this talk, the experimental searches for this phenomenon will be reviewed. Recent evidence of CT phenomenon at medium energies and future plans will be presented.

Argonne Physics Division Colloquium Schedule