  Theory predicts that quasiparticle tunneling between the counter-propagating
edges in a fractional quantum Hall state can be used to measure the effective
quasiparticle charge e* and dimensionless interaction parameter g, and thereby
characterize the many-body wavefunction describing the state. We report
measurements of quasiparticle tunneling in a high mobility GaAs two dimensional
electron system in the fractional quantum Hall state at nu=5/2 using a
gate-defined constriction to bring the edges close together. We find the
dc-bias peaks in the tunneling conductance at different temperatures collapse
onto a single curve when scaled, in agreement with weak tunneling theory.
Various models for the \nu=5/2 state predict different values for g. Among
these models, the non-abelian states with e*=1/4 and g=1/2 are most consistent
with the data.
