  We classify the irreducible unitary modules in category O for the rational
Cherednik algebras of type G(r,1,n) and give explicit combinatorial formulas
for their graded characters. More precisely, we produce a combinatorial
algorithm determining, for each r-partition of n, the closed semi-linear set of
parameters for which the contravariant form on the irreducible representation
with the given r-partition as lowest weight is positive definite. We use this
algorithm to give a closed form answer for the Cherednik algebra of the
symmetric group (recovering a result of Etingof-Stoica and the author) and the
Weyl groups of classical type.
