  We report on a search for particle dark matter with the XENON100 experiment,
operated at the Laboratori Nazionali del Gran Sasso (LNGS) for 13 months during
2011 and 2012. XENON100 features an ultra-low electromagnetic background of
(5.3 \pm 0.6) \times 10^-3 events (kg day keVee)^-1 in the energy region of
interest. A blind analysis of 224.6 live days \times 34 kg exposure has yielded
no evidence for dark matter interactions. The two candidate events observed in
the pre-defined nuclear recoil energy range of 6.6-30.5 keVnr are consistent
with the background expectation of (1.0 \pm 0.2) events. A Profile Likelihood
analysis using a 6.6-43.3 keVnr energy range sets the most stringent limit on
the spin-independent elastic WIMP-nucleon scattering cross section for WIMP
masses above 8 GeV/c^2, with a minimum of 2 \times 10^-45 cm^2 at 55 GeV/c^2
and 90% confidence level.
