  Two-particle azimuthal correlations reveal broadened and softened away-side
correlations. Several different physics mechanisms are possible: large angle
gluon radiation, deflected jets, and conical flow or Cerenkov radiation.
Three-particle correlations are investigated to try to discriminate these
mechanisms. We present results on 3-particle azimuthal correlations between a
trigger particle of 3<pT<4 GeV/c and two softer particles of 1<pT<2 GeV/c for
pp, d+Au and Au+Au collisions at sqrt(sNN) = 200 GeV. Implications of the
results are discussed.
