Sparticle Masses, $\mu $ Problem and Anomaly Mediated Supersymmetry   Breaking
  Within the MSSM framework and with purely anomaly mediated supersymmetry breaking the slepton masses turn out to be tachyonic. We resolve this problem by introducing an anomaly free U(1) gauge symmetry which provides positive $D$-term contributions to sparticle masses squared that are flavor conserving at one loop. Two realistic examples based on SU(5) are presented. With U(1) spontaneously broken at a scale $\sim 10^{16}$ GeV, the right handed neutrinos acquire masses $\stackrel{<}{_\sim}10^{14}$ GeV. This breaking scale of U(1) also plays an important role in the proposed resolution of the MSSM $\mu $ problem. 
Qaisar Shafi and Zurab Tavartkiladze