Observation of a new particle in the search for the Standard Model Higgs boson with the ATLAS detector at the LHC
Undoubtably the most significant result of the LHC to date, and possibly the most significant result in particle physics of the past decades.
With over 12.000 citations the 6-th most cited paper in particle physics all time, just after the Standard Model itself.
Its significance is not only in the fact that it proved a crucial part of the SM that was hypothetical up to then, but also that it opened up an large thus-far inaccessible part of the SM for experimental exploration (Higgs-particle interactions.
Nikhef contributed strongly to two of the three discovery decay models (WW and ZZ) and was instrumental in the development of the machinery that was used to combine the result across channels.
Link: https://inspirehep.net/literature/1124337