  In 2012, the High Energy Stereoscopic System (H.E.S.S.) was expanded by a
fifth telescope (CT5). With an effective mirror diameter of 28m, CT5 is able to
detect the Cherenkov light of very faint gamma-ray air showers, thereby
significantly lowering the energy threshold of this telescope compared to the
other four telescopes. Extracting as much information as possible from the
recorded shower image is crucial for background rejection and to reach an
energy threshold of a few tens of GeV. The camera of CT5 is conceived to
register the time of the charge pulse maximum with respect to the beginning of
the 16 ns integration window of each pixel. This information can be utilised to
improve the event reconstruction. It also helps to reduce the background
contamination at low energies. We present new techniques for background
rejection based on CT5 timing information and evaluate their performance.
