Search for challenging and long-lived signatures by ATLAS and CMS experiments

The large-hadron collider (LHC) provides a valuable opportunity to directly search for new physics signals from proton-proton collisions at TeV energy scale. This talk gives an overview of the recent searches for new physics that leave experimentally challenging signatures such as long-lived new particles, performed by ATLAS and CMS collaborations. Given that no clear indication of new physics has been observed in the extensive and many searches based on conventional signatures, these challenging searches are attracting more interests in recent.