  We develop a novel bosonic mean field theory to describe the spiral phases of
a Heisenberg antiferromagnet on a one-dimensional chain, in terms of three
bosons at each site. The ground state is disordered and for large values of the
spin $S$, two different and exponentially small energy gaps are found. The
spin-spin correlation function is computed and is shown to decay exponentially
at large distances. Our mean field theory is also shown to be exact in a
large-$N$ generalization.
