  We have calculated the expectation values of the spin and the intrinsic
magnetic moment of the gamma photons created as a result of the
electron-positron annihilation. We show that, depending on its helicity a gamma
photon propagating in z direction with an angular frequency carries a magnetic
moment of along the propagation direction. Here the (+) and (-) signs stand for
the right hand and left circular helicity respectively. e argue that in a
Stern-Gerlach experiment (SGE) the magnetic moment is an important property but
not the spin of the particles. Because of these two symmetric values of the
magnetic moment, we expect a splitting of the gamma photon beam into two
symmetric sub beams in a (SGE). We believe that the present result will be
helpful for understanding the recent attempts on the (SGE) with slow light and
the behavior of the dark polaritons and also the atomic spinor polaritons.
