Could the Higgs boson decay into dark matter? As dark matter does not interact directly with the ATLAS detector, physicists look for signs of “invisible particles”, inferred through momentum conservation of the proton–proton collision products. The ATLAS Collaboration searched the full LHC Run 2 dataset, setting the strongest limits on the Higgs boson decaying to invisible dark-matter particles to date.

The ATLAS Collaboration has just released a new result searching for the Higgs-boson decay to a Z boson and a photon. This result uses the full LHC Run 2 dataset, analysing almost four times as many Higgs-boson events as the previous ATLAS result.

A hallmark of the strong force at the Large Hadron Collider (LHC) is the dramatic production of collimated jets of particles when quarks and gluons scatter at high energies. Particle physicists have studied jets for decades to learn about the structure of quantum chromodynamics – or QCD, the theory of the strong interaction – across a wide range of energy scales. Recent theoretical and experimental advancements in their study is now allowing ATLAS physicists to test the strong force in new ways.

When a particle is transformed into its antiparticle and its spatial coordinates inverted, the laws of physics are required to stay the same – or so we thought. This symmetry – known as “CP symmetry” (Charge conjugation and Parity symmetry) – was considered to be exact until 1964, when a study of the kaon particle system led to the discovery of “CP violation”. In a new result presented today, the ATLAS Collaboration performed a direct test of the CP properties of the interaction between the Higgs boson and top quarks. The result is based on an analysis of the full LHC Run-2 dataset, looking at collision events where the Higgs boson is produced in association with one or two top quarks, and in turn decays into two photons.

Two years ago, the Higgs boson was observed decaying to a pair of beauty-quarks (H→bb), moving its study from the “discovery era” to the “measurement era”. In new results presented today, the ATLAS Collaboration studied the full LHC Run 2 dataset to give an updated measurement of H→bb, where the Higgs boson is produced in association with a vector boson (W or Z). 

A quarter-century after its discovery, physicists at the ATLAS Experiment are gaining new insight into the heaviest-known particle: the top quark. The huge amount of data collected during Run 2 of the LHC (2015-2018) has allowed physicists to study rare production processes of the top quark in great detail, including its production in association with other heavy elementary particles.

In new results presented today at CERN, the ATLAS Experiment’s search for supersymmetry (SUSY) reached new levels of sensitivity. The results examine a popular SUSY extension studied at the Large Hadron Collider (LHC): the “Minimal Supersymmetric Standard Model” (MSSM), which includes the minimum required number of new particles and interactions to make predictions at the LHC energies.

The ATLAS Collaboration at CERN has just released the first open dataset from the Large Hadron Collider’s (LHC) highest-energy run at 13 teraelectronvolts (TeV). The new release is specially developed for science education, underlining the Collaboration’s long-standing commitment to students and teachers using open-access ATLAS data and related tools. 

The electromagnetic fields of the Lorentz-contracted lead nuclei in heavy-ion collisions at the LHC act as intense sources of high-energy photons, or particles of light. This environment allows physicists to study photon-induced scattering processes, that can not be studied elsewhere. A key process examined by ATLAS physicists involves the annihilation of photons into pairs of oppositely charged muons. The ATLAS Collaboration recently released a new, comprehensive measurement of this process.

During Run 2, ATLAS achieved an exceptionally high data-quality efficiency for a hadron collider, with over 95% of the 13 TeV proton-proton collision data certified for physics analysis. In a new paper released today, the ATLAS data quality team summarises how this excellent result was achieved.