Recent results in the search for fractional charge at Stanford

In the Stanford fractional charge search experiment, we have discovered a new magnetic background effect which can be as large as 1/3 eEA. To eliminate the new effect, we can spin the ball around a vertical axis using either electric or magnetic fields, verifying the spin optically. We are proceeding with new measurements with the ball spinning so that the background effect is verifiably eliminated. At present, we do not know of a mechanism by which the distribution of residual charges observed earlier, which was sharply peaked at 0 e and ±1/3 e, could be due entirely to the magnetic effect. The effect could however have been absent if the charge-measuring electric field spun the ball during the earlier measurements. Whether it did depends on the ball's asymmetry and its damping time for spin. For the definitive answer to whether or not there are fractional charges on these niobium samples, we await our new experiments. (orig.)