Searches for New Physics in Unconventional Signatures at ATLAS

Various physics models predict new long-lived particles to be generated at the Large Hadron Collider, which leave unconventional signatures in the detectors. In order to maximise our discovery potential for new physics, the ATLAS experiment has developed novel analysis techniques for the long-lived particles. In these proceedings, a new result with $pp$ collisions at $\sqrt s = 13~\rm{TeV}$ in LHC Run 2 is presented, which exploits the ionisation energy loss measurements in the Pixel subsystem in the ATLAS detector to search for a massive charged long-lived particle with a velocity significantly below the speed of light. Several other characteristic searches performed with $pp$ collisions at $\sqrt s = 7 - 8~\rm{TeV}$ in LHC Run 1 are briefly summarised.