WIMP tracking with cryogenic nuclear emulsion

We present a novel cryogenic approach to reject the electron background that makes use of the phonon effect in nuclear emulsion. For the proof of principle, we have been investigating the sensitivity of fine-grained nuclear emulsions as a function of temperature by exposing to gamma rays and ion beams with an ion implant system in the range of 77-300 K. Results of gamma ray exposure indicate that the electron rejection power is estimated to be better than 3×10−9 at 77 K. Results of ion exposure imply that fine-grained nuclear emulsion is sensitive to ions which are light and heavy and ion tracks' angle can be measured.