  Quantum theoretical treatment of coherent forward scattering of light in a
polarized atomic ensemble with an arbitrary angular momentum is developed. We
consider coherent forward scattering of a weak radiation field interacting with
a realistic multi-level atomic transition. Based on the concept of an effective
Hamiltonian and on the Heisenberg formalism, we discuss the coupled dynamics of
the quantum fluctuations of the polarization Stokes components of propagating
light and of the collective spin fluctuations of the scattering atoms. We show
that in the process of coherent forward scattering this dynamics can be
described in terms of a polariton-type spin wave created in the atomic sample.
Our work presents a general example of entangling process in the system of
collective quantum states of light and atomic angular momenta, previously
considered only for the case of spin-1/2 atoms. We use the developed general
formalism to test the applicability of spin-1/2 approximation for modelling the
quantum non-demolishing measurement of atoms with a higher angular momentum.
