Additive preservers of Drazin Inverse of operators on B_s (H)

Let B_s (H) be the Jordan algebra of all bounded selfadjont operators on a separable Hilbert space H. In this paper we investigate and characterize all additive, one to one and onto maps \phi:B_s(H)\longrightarrow B_s(H) that preserve Drazin inverse of operators. We conclude that if for every projection operator P, we have the set \phi(\mathbb{R}P) be a subset of \mathbb{R}\phi(P) and also the relation \phi(PB_s(H)P)= \phi(P)B_s(H)\phi(P) is satisfied, then there is a unitary or anti-unitary operator U:H\rightarrow H, such that \phi(T)=UTU^*, for all T\in B_s(H).