  The physics accessible at the high-luminosity phase of the LHC extends well
beyond that of the earlier LHC program. This white paper, submitted as input to
the Snowmass Community Planning Study 2013, contains preliminary studies of
selected topics, spanning from Higgs boson studies to new particle searches and
rare top quark decays. They illustrate the substantially enhanced physics reach
with an increased integrated luminosity of 3000 fb-1, and motivate the planned
upgrades of the LHC machine and ATLAS detector.
