A Search for Light CP-Odd Higgs Bosons Decaying to mu+ mu- in ATLAS

We present a search for a very light \CP -odd Higgs boson, \aone , decaying to \mumu , using 36.7 \ipb\ of \pp\ collisions at \rts\ = 7 \TeV\ recorded by the ATLAS detector at the LHC. Such a light Higgs is predicted in Next-to-Minimal Supersymmetric Standard Models (NMSSM) designed to solve the $\mu$-term problem of the Minimal Supersymmetric Standard Model (MSSM). Its presence can significantly alter the phenomenology of the MSSM Higgs sector. We set new limits on the production cross section times branching ratio, \sigggaBamm , for \aone\ masses of 6 -- 9 \GeV\ and 11 -- 12 \GeV , avoiding the region dominated by the \Ups\ resonances.