Searching for supersymmetric Higgs bosons on the compressed frontier
The Standard Model has a number of puzzling features. For instance, why does the Higgs boson have a relatively low mass? Could its mass arise from a hidden symmetry that keeps it from being extremely heavy? And what about dark matter? While the Standard Model has some (almost) invisible particles, like neutrinos, those particles can’t account for all of the dark matter observed by cosmological measurements.
Physics Briefing | 18 Dec 2017
Squeezing sleptons at the LHC
Supersymmetry (SUSY) is an extension of the Standard Model that predicts the existence of “superpartners” with slightly different properties compared to their Standard Model counterparts. Physicists have been searching for signs of SUSY for over forty years, so far without success, which makes us think that SUSY particles — should they exist — are also heavier than particles in the Standard Model. However, in order for SUSY to help mitigate some problems with the Higgs boson sector of the Standard Model, SUSY particles should not be too heavy. And if some SUSY particles are relatively light, then they should be produced copiously at CERN’s Large Hadron Collider (LHC). So for SUSY to remain an attractive theory of nature, it must be hiding in plain sight in LHC data.
Physics Briefing | 15 Dec 2017
Explore virtual CERN with ATLAScraft
Enter the world of particle physics with the newly-launched ATLAScraft! Players can explore the CERN campus, shrink down to the size of a particle, and even conduct their own “experiments” in educational minigames.
News | 13 Dec 2017
Broken symmetry: searches for supersymmetry at the LHC
A commentary by ATLAS physicists Paul de Jong and George Redlinger on the history, progress and future of the search for supersymmetry.
Feature | 08 Dec 2017
Behind the scenes at ATLAS Week
A few times a year, the large LHC collaborations such as ATLAS organise an internal overview session. This photo essay will take you to the most recent of these “ATLAS Weeks” – giving you a glimpse behind the curtain, and exploring this essential part of the collaboration structure and life.
News | 06 Nov 2017
Noble nuclei open new doors in ATLAS physics
Take something you think you understand, change it and see what happens. Earlier this month, the ATLAS Experiment put this basic scientific principle to the test during the first Large Hadron Collider (LHC) xenon run.
News | 31 Oct 2017
ATLAS finds evidence of the Higgs boson produced in association with a pair of top quarks
The ATLAS collaboration has presented evidence of “ttH production”, a rare process where a pair of top quarks emits a Higgs boson. Observing this process would provide new insight into the Higgs mechanism and allow for new studies of how unknown physics might (or might not) change the behaviour of this fundamental particle.
Physics Briefing | 26 Oct 2017
Photon-tagged jet quenching in the quark-gluon plasma
Collisions of lead nuclei in the LHC form the hot, dense medium known as the quark-gluon plasma (QGP). Experimentally, the QGP is characterized by the collective flow of emerging quarks and gluons. They fragment into highly collimated “jets” of particles that in turn lose energy through a phenomenon known as “jet quenching”. Studying this effect can help improve our understanding of quantum chromodynamics, the theory of the strong nuclear interaction that governs the behaviour of the QGP.
Physics Briefing | 23 Oct 2017
Studying fragments of the top quark
Using Run 1 data, ATLAS reports a new differential production rate measurement of top quark pairs and a precise new determination of the top quark mass.
Physics Briefing | 05 Oct 2017
The art of physics
I have been doing some work with artists recently. Not that I’m planning a career change, you know: I just love to talk about my research to anyone who is prepared to listen, and lately it’s been with artists. Ruth Jarman and Joe Gerhardt, aka Semiconductor, are internationally renowned visual artists who in 2015 won the Collide@CERN Ars Electronica Award and spent a two-month residency at CERN. Like myself, they live in Brighton, which is also home to the University of Sussex, where I work.
Blog | 04 Oct 2017
Hunting down forbidden decays of the top quark
Ordinary matter is made of just three kinds of elementary particles: up and down quarks, which form the atomic nucleus, and electrons, which surround the nucleus. But the rest of nature is not so straightforward: heavier forms of quarks and leptons are produced regularly at particle accelerators.
Physics Briefing | 03 Oct 2017
ATLAS LIVE: Celebrating 25 years of discovery
To celebration of its 25th anniversary, ATLAS is hosting a series of Facebook live events today, Monday 2 October 2017. Explore key locations around CERN - including the ATLAS control room, Building 40 and the ATLAS TileCal workshop - while learning about the physics, construction and history of the ATLAS Experiment.
News | 02 Oct 2017
ATLAS and CMS look forward with the top quark
The top quark, the heaviest known elementary particle, has a unique place in the Standard Model. By precisely measuring its properties, ATLAS physicists can probe physics beyond our current understanding.
Physics Briefing | 27 Sep 2017
On top of the top: ATLAS highlights from the TOP2017 workshop
The ATLAS collaboration presented exciting new results at the 10th International Workshop on Top Quark Physics (TOP2017), held in Braga (Portugal). The conference, which concluded today, brought together experimental and theoretical physicists specializing in the heaviest known elementary particle: the top quark.
News | 22 Sep 2017
Finding a haystack in a field of haystacks
In order to produce rare physics phenomena, such as the Higgs boson or possible signs of new physics, the Large Hadron Collider (LHC) collides tens of millions of protons per second. Under such conditions, around 20 simultaneous proton-proton interactions occur in each beam crossing. Thus, additional collisions called “pile-up” are recorded along with the collision of interest. Together, they form a single event for analysis.
Physics Briefing | 22 Sep 2017
Exploring the nature of the “ridge” in small systems
When ultra-relativistic heavy ions collide, a new state of hot and dense matter – the quark–gluon plasma (QGP) – is created. One of the key features for this state is the observation of long-range azimuthal angle correlations between particles emitted over a wide range of pseudorapidity. This phenomenon is often referred to as the “ridge”.
Physics Briefing | 28 Aug 2017
ATLAS sees first direct evidence of light-by-light scattering at high energy
Physicists from the ATLAS experiment at CERN have found 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 today in Nature Physics, confirms one of the oldest predictions of quantum electrodynamics (QED).
Press Statement | 14 Aug 2017
Exploring rare decays of the Higgs boson
Since discovering a Higgs boson in 2012, the ATLAS and CMS collaborations have been trying to understand whether this new particle is the Higgs boson as predicted by the Standard Model, or a Higgs boson from a more exotic model containing new, as yet undiscovered, particles. The answer lies in the properties of the Higgs boson.
Physics Briefing | 11 Aug 2017
5 fundamental parameters from top quark decay
For many physicists, discovering “new physics” means bringing to light a new particle. Another path to discovery lies in carefully measuring the properties of known particles and the interactions between them. The ATLAS experiment has now released new results on the top quark's interaction with the charged intermediate vector boson.
Physics Briefing | 03 Aug 2017
The invisible plan
As the Large Hadron Collider (LHC) smashes together protons at a centre-of-mass energy of 13 TeV, it creates a rich assortment of particles that are identified through the signature of their interactions with the ATLAS detector. But what if there are particles being produced that travel through ATLAS without interacting? These “invisible particles” may provide the answers to some of the greatest mysteries in physics.
Physics Briefing | 17 Jul 2017
ATLAS highlights from EPS-HEP 2017
The ATLAS Collaboration has presented important new results at the European Physical Society conference on High Energy Physics (EPS-HEP) in Venice (Italy), including the latest analyses of 13 TeV Run 2 data from the Large Hadron Collider (LHC).
News | 12 Jul 2017
Probing physics beyond the Standard Model with heavy vector bosons
Although the discovery of the Higgs boson by the ATLAS and CMS Collaborations in 2012 completed the Standard Model, many mysteries remain unexplained. For instance, why is the mass of the Higgs boson so much lighter than one would expect and why is gravity so weak?
Physics Briefing | 08 Jul 2017
New rare pairs of heavy friends in ATLAS
Observing rare productions of heavy elementary particles can provide fresh insight into the Standard Model of particle physics. In a new result, the ATLAS Experiment presents strong evidence for the production of a single top-quark in association with a Z boson.
Physics Briefing | 07 Jul 2017
Why should there be only one? Searching for additional Higgs Bosons beyond the Standard Model
Since the discovery of the elusive Higgs boson in 2012, researchers have been looking beyond the Standard Model to answer many outstanding questions. An attractive extension to the Standard Model is Supersymmetry (SUSY), which introduces a plethora of new particles, some of which may be candidates for Dark Matter.
Physics Briefing | 06 Jul 2017
New ATLAS measurement of the Higgs Boson mass
The ATLAS collaboration has released a new preliminary measurement of the Higgs boson mass using 2015 and 2016 LHC data. The number of recorded Higgs boson events has more than tripled since the first measurement of the Higgs boson was released, using 2011/2012 data. An improved precision in the measurement of the Higgs boson mass has been made possible by both the increased collision energy of 13 TeV and improved collision rate.
Physics Briefing | 06 Jul 2017