  The precise determination of the masses of the CP-odd and -even heavy Higgs
bosons is an important part of the study of Supersymmetry and its relation with
cosmology through dark matter. This note presents a determination of the A0
boson mass with the e+e- -> H0A0 -> b b b b process for a dark matter motivated
cMSSM scenario with M(A) = 1141 GeV at CLIC. The analysis is performed with
full simulation and reconstruction at 3 TeV accounting for beamstrahlung
effects. SM and SUSY backgrounds are considered and the effect of the overlay
of gamma gamma -> hadrons events on the signal is studied for various
assumptions for the detector time-stamping capabilities. The di-jet mass
resolution is improved by applying a kinematic fit. The A0 mass can be
determined with a statistical accuracy of ~3-5 GeV for 3 inverse ab of
statistics and 0 to 20 bunch crossings of gamma gamma background integrated in
one event, respectively.
