Briefings
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.
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.
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.
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.
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.
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).
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.
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.
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).
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.
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.
Teaching established software new tricks
Following several years of development, ATLAS Collaboration has launched a new "multithreaded" release of its analysis software, Athena.
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.
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.
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.
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).
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'.
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.
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.
Studying “Little Bangs”: exotic collisions probe the size of quark-gluon plasma
A new result from the ATLAS Collaboration studies the interactions of photons – particles of light – with lead nuclei at the Large Hadron Collider (LHC). Using new data collection techniques, physicists revealed an unexpected similarity to the experimental signatures of the quark–gluon plasma.
The hunt for higgsinos reaches new limits
The ATLAS Collaboration has released three new searches for "higgsinos" - the super-partner of the Higgs boson.
Heavyweight champions: a search for new heavy W’ bosons with the ATLAS detector
A new search from the ATLAS Collaboration, released this week at the Large Hadron Collider Physics conference (LHCP 2021), sets limits on the mass of the W’ boson.
ATLAS measures the polarisation of top quarks and antiquarks
In a new result presented by the ATLAS Collaboration, physicists have measured – for the first time – the full polarisation vectors for both top quarks and antiquarks.
New search for charming decay of the Higgs boson
At the LHCP2021 conference, the ATLAS Collaboration presents a new direct search for the decay of the Higgs boson to charm quarks. Observing this decay would give physicists new insight into the Higgs boson’s relationship with the second generation of matter particles.
Twice the Higgs, twice the challenge
In the post-Higgs discovery era, scientists at the Large Hadron Collider (LHC) have been hard at work studying the Higgs boson’s properties. One property that remains to be experimentally verified is whether the Higgs boson can couple to itself (self-coupling).