ATLAS finds evidence of spectacular four-top quark production

26th May 2020 – In a new result released today, the ATLAS Collaboration announced strong evidence of the production of four top quarks. This rare Standard Model process is expected to occur only once for every 70 thousand pairs of top quarks created at the LHC and has proven extremely difficult to measure.

Read more →

ATLAS measures light scattering on light and constrains axion-like particles

25th May 2020 – Light-by-light scattering is a very rare phenomenon in which two photons – particles of light – interact, producing another pair of photons. Direct observation of this process at high energy had proven elusive for decades, until it was first seen by the ATLAS Collaboration in 2016 and established in 2019. In a new measurement, ATLAS physicists are using light-by-light scattering to search for a hyped phenomenon beyond the Standard Model of particle physics: axion-like particles.

Read more →

Summary of new ATLAS results from LHCP 2020

25th May 2020 – The eighth annual conference on Large Hadron Collider physics (LHCP 2020) kicks off today in video-conference rooms around the world. This week-long event is usually an opportunity for physicists from around the world to meet in person and share the latest news from their LHC experiments. This year, due to the COVID-19 pandemic, the conference is being held online.

Read more →

Machine learning qualitatively changes the search for new particles

13th May 2020 – The ATLAS Collaboration is exploring novel ways to search for new phenomena. Alongside an extensive research programme often inspired by specific theoretical models – ranging from quantum black holes to supersymmetry – physicists are applying new model-independent methods to broaden their searches. ATLAS has just released the first model-independent search for new particles using a novel technique called “weak supervision”.

Read more →

Probing dark matter with the Higgs boson

21st April 2020 – 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.

Read more →

ATLAS searches for rare Higgs boson decays into a photon and a Z boson

21st April 2020 – 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.

Read more →

Novel probes of the strong force: precision jet substructure and the Lund jet plane

19th April 2020 – 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.

Read more →

Searching for new sources of matter–antimatter symmetry breaking in Higgs boson interaction with top quarks

7th April 2020 – 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.

Read more →

Measuring the beauty of the Higgs boson

7th April 2020 – 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). 

Read more →

ATLAS Collaboration enters active “Safe Mode”

2nd April 2020 – The global health crisis caused by COVID-19 has impacted every aspect of life. Much of the world’s population are sheltering in place, with ATLAS Collaboration members similarly affected. 

Read more →

Pages