The Higgs boson is observed decaying into a pair of bottom quarks for the first time. This elusive interaction is predicted to make up almost 60% of the Higgs boson decays and is thus primarily responsible for the Higgs natural width.

ATLAS announces the observation of Higgs bosons produced together with a top-quark pair. This rare process is one of the most sensitive tests of the Higgs mechanism and its observation marked a significant milestone for the field of High-Energy Physics.

ATLAS publishes the first direct evidence of high energy light-by-light scattering, a very rare process in which two photons – particles of light – interact and change direction. The result, published in Nature Physics, confirms one of the oldest predictions of quantum electrodynamics.

ATLAS sees the first LHC evidence of the Higgs boson decaying to a pair of b-quarks. Despite being the dominant Higgs decay, finding evidence in this channel was a major challenge. Following years of dedicated search, ATLAS was able to spot this elusive decay in 2017, with an observed significance of 3.6 σ (expectation 4.0 σ) when combining the Run 1 and Run 2 datasets.

ATLAS begins preparations for the Phase II upgrade of the experiment, which will be in place for the High-Luminosity LHC. This upgraded ATLAS experiment will begin data taking in 2026.

ATLAS shows its strength for precision physics, taking a world-class measurement of the W boson mass. Precise measurements of the W boson mass are vital, as the parameter is related in the Standard Model to the masses of the top quark and the Higgs boson. Measuring the W mass can thus test the self-consistency of the Standard Model, since any deviation from the predicted relation would be a sign of new physics. This first ATLAS result is consistent and as precise as the best previous measurement of the W mass.

The ATLAS and CMS Experiments release combined measurements of the Higgs boson production and decay rates. Examining all data from the LHC Run-1, the result gives a snapshot of the world’s knowledge of the mysterious Higgs boson. In addition to setting constraints on Higgs couplings to vector bosons and fermions, the combination established the observation of Higgs to di-tau decay and weak-boson-fusion production.

ATLAS began recording physics data from 13 TeV proton collisions, which allow for precision studies of the Higgs boson and other Standard Model particles, as well as the search for new particles with higher masses.

ATLAS publishes first evidence for electroweak production of W bosons with the same charge. This channel receives contributions from quartic interactions between W bosons. This rare process gives physicists a new way to study electroweak symmetry breaking and to indirectly probe the properties of the Higgs boson.

The 2013 Nobel Prize in physics is awarded to Professors François Englert and Peter Higgs "for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles, and which recently was confirmed through the discovery of the predicted fundamental particle, by the ATLAS and CMS experiments at CERN’s Large Hadron Collider". ATLAS and CMS physicists cheered the announcement.