VLADD : An Extra Dimensions Detector

The existence of extra-dimensions may be detected by observing the invisible decay of orthopositronium (oPs) at a branching ratio of $10^{- 10}$. Previous experiments have searched for invisible decays at a branching ratio of $10^{-6}$ but were unable to achieve greater precision due to electron backgrounds. None of these experiments attempted to utilize a detector which would distinguish positrons from electrons. The VLADD experiment proposes to use a mini-TPC placed in a small, stable magnetic field as a means to separate $e^+$ from $e^-$. VLADD will be a demonstration experiment to verify that this technique will in fact work and will allow adequate rejection of backgrounds. Should the techniques used in VLADD reach a branching ratio sensitivity on the order of the most sensitive current measurements ($10^{-6}$), then a proposal will be made to build a larger version of VLADD for a more sensitive extra-dimensions search.