Briefings

ATLAS looks for top quarks going against the current

Using the full Run-2 dataset, the ATLAS Collaboration has published four analyses searching for flavour-changing neutral currents in the production and decay of the top quark. The results study top-quark processes involving all four neutral bosons: the photon, gluon, Z boson and Higgs boson. 

Physics Briefing | 16 May 2022

Mass matters – but it isn't the only thing!

The ATLAS Collaboration finds evidence of parton mass, colour-charge and radiation-pattern dependence in quark-gluon-plasma induced energy loss.

Physics Briefing | 27 April 2022

ATLAS gives new insight into dijet suppression in heavy-ion collisions

At the recent Quark Matter 2022 conference in Krakow, Poland, members of the ATLAS Collaboration presented a new study of “jets” of particles travelling through the QGP. The result provides new insight into dijet suppression due to interactions with the nuclear medium.

Physics Briefing | 22 April 2022

ATLAS observes pairs of tau particles in heavy-ion collisions

Today at the Quark Matter 2022 Conference, the ATLAS Collaboration announced the observation of tau-lepton pairs created when particles of light – or photons – interact during lead-ion collisions. The result opens a new avenue for measuring how magnetic the tau lepton is – a property sensitive to new particles beyond the Standard Model. 

Physics Briefing | 7 April 2022

ATLAS strengthens its search for supersymmetry

Where is all the new physics? Could it be sneaking past the standard searches? ATLAS researchers have developed innovative ways to search for new particles, improving their search programme to ensure they have the best chance of discovering new physics in Run 3 of the LHC.

Physics Briefing | 29 March 2022

Search for new physics in Higgs boson decays with displaced photons

The ATLAS Collaboration performed a new search for exotic Higgs-boson decays using the full dataset of 13 TeV proton-proton collisions delivered by the LHC between 2015 and 2018.

Physics Briefing | 28 March 2022

One Higgs boson found – could there be more?

Many theories suggest that the Higgs boson discovered in 2012 by the ATLAS Experiment is but the first to be observed from a larger Higgs family. A new ATLAS analysis searches for the presence of a new singly-charged Higgs boson.

Physics Briefing | 24 March 2022

ATLAS reports first observation of single top-photon production

The ATLAS Collaboration announces the first observation of “tqγ production”: the associated production of a single top quark and a photon in proton-proton collisions at the LHC.

Physics Briefing | 15 March 2022

ATLAS seeks out unusual signatures of long-lived particles

The ATLAS Collaboration has devised a range of new strategies to look for long-lived particles with various possible characteristics. Four new results from this effort were presented at the recent Lepton-Photon and La Thuile conferences.

Physics Briefing | 14 March 2022

ATLAS event selection system readies for LHC Run 3

The ATLAS trigger system operated extremely successfully during Run 1 (2009–2013) and Run 2 (2015–2018) of the LHC. It is now undergoing various upgrades in preparation for the upcoming Run-3 data-taking period, which will see a moderate increase in the rate of collisions inside the experiment.

Experiment Briefing | 28 February 2022

Looking for the invisible with the Higgs boson

According to the Standard Model, most particles get their mass through an interaction with the Higgs field. If dark-matter particles acquire their mass in the same way, a Higgs boson created in an LHC collision might sometimes decay into a pair of “invisible” dark-matter particles. The ATLAS Collaboration has released a new search for invisible Higgs-boson decays using the full Run-2 dataset.

Physics Briefing | 17 February 2022

ATLAS sees a difference between beauty and charm decays of the Higgs boson

Physicists from the ATLAS Collaboration have combined two measurements of the interaction strength of the Higgs boson with two different pairs of quarks. This allows physicists to test a hypothesis that the Higgs boson interacts with charm quarks (which are second-generation quarks) in the same way it interacts with beauty quarks (third-generation quarks).

Physics Briefing | 1 February 2022

Upgraded ATLAS Liquid Argon Calorimeter ready for next LHC operation

The ATLAS Collaboration has completed the installation of “Phase-I” upgrades of the Liquid Argon Calorimeter (LAr). The upgrades improve the read-out speed of the calorimeter’s electronics and provide more efficient event-selection capabilities. These improvements will be pivotal for data-taking during the coming high-intensity runs of the LHC.

Experiment Briefing | 25 January 2022

ATLAS gives new insight into the internal structure of the proton

The ATLAS Collaboration has just released a new paper combining LHC and HERA data to determine Parton Distribution Functions (PDFs), which describe what fraction of a proton’s momentum is taken by its constituent quarks and gluons. 

Physics Briefing | 12 January 2022

Discovery channels join forces for detailed investigation of the Higgs boson

The ATLAS Collaboration has released updated measurements of the Higgs boson properties using the full LHC Run-2 dataset (recorded 2015-2018).

Physics Briefing | 11 January 2022

New ATLAS result seeks to unravel the charge–flavour mystery

Could there be another source of asymmetry in the Universe? ATLAS physicists are studying the differences between positively- and negatively-charged electrons and muons, looking for signs of charge–lepton-flavour symmetry breaking.

Physics Briefing | 17 December 2021

Search for elusive “di-Higgs production” reaches new milestone

According to the Standard Model, the Higgs boson can interact with itself, resulting in the simultaneous production of two Higgs bosons ("di-Higgs production"). In a new result, the ATLAS Collaboration combines three di-Higgs decay channels to reach the best limits yet on di-Higgs production.

Physics Briefing | 19 November 2021

Teaching established software new tricks

Following several years of development, ATLAS Collaboration has launched a new "multithreaded" release of its analysis software, Athena.

Experiment Briefing | 15 October 2021

Searching for new physics using asymmetric top-quark events

Finding the differences between these types of matter – while extremely challenging – could reveal well-hidden effects that hint at the existence of new particles and interactions. In a new result presented at the TOP 2021 conference, the ATLAS Collaboration probed the heaviest-known elementary particle, the top quark, in search of these effects.

Physics Briefing | 13 September 2021

Hunting for forbidden decays of the Z boson

In a new study, the ATLAS Collaboration looked for Z bosons decaying into an electron and an anti-muon, or into a muon and a positron.

Physics Briefing | 3 August 2021

ATLAS measures key Higgs boson interaction with high precision

The ATLAS Collaboration releases new measurements of the Higgs-boson decay to tau leptons. The result provides new insight into the “Yukawa coupling”, a key interaction of the Higgs boson. 

Physics Briefing | 2 August 2021

Two Higgs bosons are better than one

One of the long-term goals of the LHC is to measure the Higgs-boson self-coupling, which in turn can give us clues about the formation of the early Universe. This self-coupling can only be measured directly by studying the production of pairs of Higgs bosons (HH). 

Physics Briefing | 30 July 2021

Probing new physics with pairs of Higgs bosons

The ATLAS Collaboration has released a new result searching for pairs of Higgs bosons (HH) produced by new particles. The Higgs bosons would then each decay into pairs of bottom (b) quarks – known as the '4b decay channel'.

Physics Briefing | 28 July 2021

ATLAS reports first observation of WWW production

The ATLAS Collaboration announces the first observation of “WWW production”: the simultaneous creation of three massive W bosons in high-energy LHC collisions.

Physics Briefing | 26 July 2021

Shining light on the strong interaction: ATLAS measures photon pair production

What can particles of light – photons – tell us about the inner workings of the Standard Model? A new paper from the ATLAS Collaboration measures pairs of photons to improve the understanding of a fundamental force of Nature – the strong force – and thus scrutinise the theoretical models that underpin high-energy physics research. 

Physics Briefing | 22 July 2021