Intensity correlation and anticorrelations in coherently prepared atomic vapor

Motivated by the recent experiment [V.A. Sautenkov, Yu.V. Rostovtsev, and M.O. Scully, Phys. Rev. A 72, 065801 (2005)], we develop a theoretical model in which the field intensity fluctuations resulted from resonant interaction of a dense atomic medium with laser field having finite bandwidth. The intensity-intensity cross correlation between two circular polarized beams can be controlled by the applied external magnetic field. A smooth transition from perfect correlations to anti-correlations (at zero delay time) of the outgoing beams as a function of the magnetic field strength is observed. It provides us with the desired information about decoherence rate in, for example, $^{87}$Rb atomic vapor.