roll off dactor and flat sidelobe level - what are they?

The gain of the antennas of H-BS AH(φ) at an angle φ with respect to its boresight and the ground receiver antenna AU (Θ) at an angle Θ away from its boresight are approximated by a cosine function raised to a power roll-off factor n, with a flat sidelobe level sf.

AU=GU*max[cos(Θ)^nU, sf]

what are the roll off dactor and flat sidelobe level?