Heather Ray 
   VLADD : VLAnd 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.