http://www.sciencedaily.com/releases/2012/06/120613145418.htm
snip In a study to appear in the June 14 issue of the journal Nature, the Princeton-led team, which included scientists from Los Alamos National Laboratory (LANL) and the University of California-Irvine, used direct imaging of electron waves in a crystal. The researchers did so not only to watch the electrons gain mass but also to show that the heavy electrons are actually composite objects made of two entangled forms of the electron. This entanglement arises from the rules of quantum mechanics, which govern how very small particles behave and allow entangled particles to behave differently than untangled ones. Combining experiments and theoretical modeling, the study is the first to show how the heavy electrons emerge from such entanglement.