ATLAS kicks off a new year at 13 TeV

23rd May 2017 – Geneva, 23 May 2017. A new season of record-breaking kicked off today, as the ATLAS Experiment began recording first data for physics of 2017. This will be the LHC’s third year colliding beams at an energy of 13 tera electron volts (TeV), allowing the ATLAS Experiment to continue to push the limits of physics.

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ATLAS Highlights from LHCP

23rd May 2017 – The fifth annual Large Hadron Collider Physics (LHCP2017) conference was held this week at Shanghai Jiao Tong University in a leafy suburb in the former French concession in Shanghai, China. This year there were more participants than ever before: 470 people from universities across the globe. ATLAS presented an interesting set of new results exploiting the high statistics of the combined 2015 and 2016 dataset.

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ATLAS at the starting line

19th May 2017 – The start of the 2017 run marks the conclusion of a maintenance period known as the Extended Year-End-Technical-Stop (EYETS). This upkeep is vital for the health and well-being of the detector, ensuring that ATLAS can thrive for the months of high-intensity operation that follow.

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ATLAS releases new results in search for weakly-interacting supersymmetric particles

18th May 2017 – Supersymmetry is an extension to the Standard Model that may explain the origin of dark matter and pave the way to a grand unified theory of nature. For each particle of the Standard Model, supersymmetry introduces an exotic new “super-partner,” which may be produced in proton-proton collisions. Searching for these particles is currently one of the top priorities of the LHC physics program. A discovery would transform our understanding of the building blocks of matter and the fundamental forces, leading to a paradigm shift in physics similar to when Einstein’s relativity superseded classical Newtonian physics in the early 20th century.

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Hunting for the superpartner of the top quark

17th May 2017 – Supersymmetry (SUSY) is one of the most attractive theories extending the Standard Model of particle physics. SUSY would provide a solution to several of the Standard Model’s unanswered questions, by more than doubling the number of elementary particles, giving each fermion a bosonic partner and vice versa. In many SUSY models the lightest supersymmetric particle (LSP) constitutes dark matter.

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New ATLAS precision measurements of the Higgs Boson in the 'golden channel'

15th May 2017 – With the huge amount of proton–proton collisions delivered by the LHC in 2015 and 2016 at the increased collision energy of 13 TeV, ATLAS has entered a new era of Higgs boson property measurements. The new data allowed ATLAS to perform measurements of inclusive and differential cross sections using the “golden” H->ZZ*->4l decay.

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New insight into the Standard Model

9th May 2017 – Ever since the LHC collided its first protons in 2009, the ATLAS Collaboration has been persistently studying their interactions with increasing precision. To this day, it has always observed them to be as expected by the Standard Model. Though it remains unrefuted, physicists are convinced that a better theory must exist to explain certain fundamental questions: What is the nature of the dark matter? Why is the gravitational force so weak compared to the other forces?

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Making the most of the ATLAS detector

2nd May 2017 – Up to now, ATLAS has measured the energies and positions of jets using the finely segmented calorimeter system, in which both electrically charged and neutral particles interact. However, the inner detector tracking system provides more precise measurements of charged particle energies and positions. A recent ATLAS paper describes a particle flow algorithm that extrapolates the charged tracks seen by the inner detector to the calorimeter regions. 

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Beams return to the ATLAS Experiment

29th April 2017 – With the year’s first proton beams now circulating in the Large Hadron Collider, physicists have today recorded “beam splashes” in the ATLAS experiment

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Charged-particle reconstruction at the energy frontier

26th April 2017 – A new age of exploration dawned at the start of Run 2 of the Large Hadron Collider, as protons began colliding at the unprecedented centre-of-mass energy of 13 TeV. The ATLAS experiment now frequently observes highly collimated bundles of particles (known as jets) with energies of up to multiple TeV, as well as tau-leptons and b-hadrons that pass through the innermost detector layers before decaying. These energetic collisions are prime hunting grounds for signs of new physics, including massive, hypothetical new particles that would decay to much lighter  and therefore highly boosted  bosons. 

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Impressions from Moriond

6th April 2017 – The 52nd Rencontres de Moriond conference was held in La Thuile, Italy, from the 18 March to 1 April. The first week, which ran until 25 March, was devoted to the theme "Electroweak interactions and unified theories", while the second week was based on the theme of “QCD and high energy interaction”.

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Searching for new symmetries of nature

6th April 2017 – The fundamental forces of nature are intimately related to corresponding symmetries. For example, the properties of electromagnetic interactions (or force) can be derived by requiring the theory that describes it to remain unchanged (or invariant) under a certain localised transformation. Such an invariance is referred to as a symmetry, just as one would refer to an object as being symmetric if it looks the same after being rotated or reflected. The particular symmetry related to the forces acting among particles is called gauge symmetry.

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Improving our understanding of photon pairs

5th April 2017 – High-energy photon pairs at the LHC are famous for two things. First, as a clean decay channel of the Higgs boson. Second, for triggering some lively discussions in the scientific community in late 2015, when a modest excess above Standard Model predictions was observed by the ATLAS and CMS collaborations.

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ATLAS highlights from Moriond

2nd April 2017 – At this year’s Rencontres de Moriond, the ATLAS collaboration presented the first results examining the combined 2015/2016 LHC data at 13 TeV proton–proton collision energy. Thanks to outstanding performance of the CERN accelerator complex last year, this new dataset is almost three times larger than that available at ICHEP, the last major particle physics conference held in August 2016.

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Quest for the lost arc

21st March 2017 – Nature has surprised physicists many times in history and certainly will do so again. Therefore, physicists have to keep an open mind when searching for phenomena beyond the Standard Model.

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Particle-hunting at the energy frontier

20th March 2017 – There are many mysteries the Standard Model of particle physics cannot answer. Why is there an imbalance between matter and anti-matter in our Universe? What is the nature of dark matter or dark energy? And many more. The existence of physics beyond the Standard Model can solve some of these fundamental questions. By studying the head-on collisions of protons at a centre-of-mass energy of 13 TeV provided by the LHC, the ATLAS Collaboration is on the hunt for signs of new physics.

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Searching for signs of the “stop”

20th March 2017 – In new results presented at the Moriond Electroweak conference, the ATLAS Collaboration has sifted through the full available data sample of the LHC’s 13 TeV proton collisions in search of a specific SUSY particle: the heavy partner to the top quark, called the “top squark” or “stop”

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The search for super-particles continues!

20th March 2017 – Many of the most important unanswered questions in fundamental physics are related to mass. Why do elementary particles, which we have observed and measured at CERN and other laboratories, have the masses they do? And why are they so different, with the mass of the top quark more than three hundred thousand times that of the electron? The presence of dark matter in our universe is inferred because of its mass but, if it is a particle, what is it? While the Standard Model has been a tremendously successful theory in describing the interactions of sub-atomic particles, we must look to even larger masses in search of answers and, potentially, new supersymmetric particles

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ATLAS to present new results at Moriond

19th March 2017 – Every March for the past 50 years, particles physicists have been heading to the mountains. The terminus of this migration? Les Rencontres de Moriond, one of the year’s first major conference for high-energy physics.

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ATLAS Spokesperson Karl Jakobs

New Management at the ATLAS Experiment

3rd March 2017 – Karl Jakobs from the University of Freiburg is a familiar face at CERN and in the ATLAS Experiment. He’s been part of the collaboration since the signing of the ATLAS Letter of Intent in 1992, having taken on various coordination roles, and followed the experiment through all its phases. Now, after twenty-five years with the collaboration, Karl is moving into the main office as spokesperson.

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