The well known left-handed asymmetry in the weak interaction is about the only way to let someone in a distant galaxy know what we mean by right and left.  However, the energy dependence of this asymmetry is fertile ground to explore new physical phenomena, since the standard model makes quite firm predictions, but measurements are not quite there yet.  This experiment utilizes ultra-cold neutrons (UCN).  UCN scatter elastically off nuclei and can thus be contained just like a ball in a box.  In this experiment the box is non-magnetic so if the UCN are put in to the box polarized they tend to stay polarized.  Once in the box a UCN bounces around until it decays into a proton, neutrino, and electron; the electron is then captured by the detectors in the box and it's energy and position are logged.  The A-correlation is the energy dependence of asymmetry in the electrons direction relative to the neutrons polarization.  This experiment is being done at the Los Alamos Neutron Science Center (LANCSE) by an international collaboration.