  The H -> mu mu signature provides excellent mass resolution for Higgs bosons,
and is therefore an important Higgs boson decay channel despite the small
dimuon branching ratio. We present an optimization of selection criteria in a
search for trilepton ttH (H -> mu mu) events, in which the top quark pair
decays semi-leptonically, at a simulated High Luminosity LHC (HL-LHC) running
at 14 TeV. The study is performed with 3000 fb^(-1) of simulated data with an
average pileup of < mu > = 140. In this ultimate HL-LHC data set, we find that
ttH (H -> mu mu) will be a very difficult signature to observe due to the very
small expected signal.
