Updates tagged: “Physics Results”

More than the sum of its parts: inside the proton

Discovered almost 100 years ago by Ernest Rutherford, the proton was one of the first particles to be studied in depth. Yet there’s still much about it that remains a mystery. Where does its mass and spin come from? What is it made of? To answer these questions, ATLAS physicists are using “jets” of particles emitted by the LHC as a magnifying glass to examine the inner structure of the proton.

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ATLAS Highlights from LHCP

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 releases new results in search for weakly-interacting supersymmetric particles

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of matter and the fundamental forces, leading to a paradigm shift in physics similar to when Einstein’s relativity superseded classical Newtonian physics in the early 20th century.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

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'

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

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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Searching for new symmetries of nature

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

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

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

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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