Briefings

Hunting for new physics with boosted bosons

The Standard Model is a tremendously successful theory that describes our best understanding of elementary particles and their interactions, and even predicted the existence of the Higgs Boson. It does not however explain ~95% of the known universe – including dark matter and dDark energy – and does not include a description of gravity.

Physics Briefing | 6th August 2016

Double the bosons, double the excitement

ATLAS has performed measurements of boson-pair production using data from 13 TeV proton-proton collisions that began in 2015. The cross-section (a measure of the production frequency) of the WW boson pair production was measured and was compared to a previous measurement in 8 TeV collisions.

Physics Briefing | 5th August 2016

High-mass di-photon resonances: the first 2016 ATLAS results

One of the highlights of last year’s physics results was the appearance of an excess in the search for a new particle decaying into two photons ("the di-photon channel"). New results in this channel were presented at the ICHEP conference in Chicago on Friday, 5 August.

Physics Briefing | 5th August 2016

ATLAS observes the Higgs boson with Run 2 data

The LHC’s jump in energy to 13 TeV in Run 2, together with the copious amount of collisions delivered over the last 12 months, has allowed the ATLAS experiment to collect a data sample that is more than equivalent to the one collected during Run 1.

Physics Briefing | 4th August 2016

Further progress in the quest for SUSY particles

ATLAS physicists have been eagerly searching the collected data for evidence of the production of the supersymmetric top quark (squark). Recent ATLAS results feature five separate searches for this elusive particle.

Physics Briefing | 4th August 2016

Hunting the origin of the top quark’s mass

The ATLAS experiment has been searching for the process in which a pair of top quarks is produced, where one is a “virtual” particle that emits a Higgs boson on the way to becoming a “real” particle. This process is referred to as ttH production after the particles that are produced.

Physics Briefing | 4th August 2016

Searching for new phenomena in final states with missing momentum and jets

The nature of dark matter remains one of the greatest mysteries in physics. While extraordinary, the Standard Model can not explain dark matter, whose existence is well established by cosmological measurements.

Physics Briefing | 4th August 2016

Continuing the search for extra dimensions

For a long time, physicists have assumed that space-time has four dimensions in total – three of space and one of time – in agreement with what we see when we look around us. However, some theorists have proposed that there may be other spatial dimensions that we don’t experience in our daily lives.

Physics Briefing | 17th June 2016

Di-photons in the spotlight

The ATLAS collaboration has now released the final results on the search for new physics in the di-photon channel using 2015 data.

Physics Briefing | 17th June 2016

Something went bump in the night

ATLAS has published hundreds of studies of LHC data, with the Higgs boson discovery being perhaps the best known. Amongst the Run 1 searches there was one which stood out: the diboson excess.

Physics Briefing | 16th June 2016

A peek inside the proton…

When the protons from the LHC collide, they sometimes produce W and Z bosons, the massive carriers of the weak force responsible for radioactive decays. These bosons are produced in abundance at the LHC and ATLAS physicists have now precisely measured their production rates using 13 TeV proton-proton collision data recorded in 2015.

Physics Briefing | 16th June 2016

Weighing in on the top quark mass

ATLAS has released a new precise measurement of the mass of the top quark, the heaviest known elementary particle.

Physics Briefing | 15th June 2016

Stacking the building blocks of the 2016 ATLAS physics programme

2016 is set to be an outstanding year for the ATLAS experiment and the Large Hadron Collider. We’re expecting up to 10 times more data compared to 2015, which will allow us to make precise measurements of many known physics processes and to search for new physics.

Physics Briefing | 13th June 2016

The search for the dark side of the Universe

ATLAS scientists have just released a new publication with results based on an analysis of the early Run 2 data collected in 2015 using 13 TeV proton-proton collisions.

Physics Briefing | 13th April 2016

Wanted: SUSY particle still at large

According to classical electrodynamics, the electromagnetic energy (and mass) of a point-like electron should be infinite. This is of course not the case! The solution of the riddle is antimatter - the ‘vacuum’ around every electron is filled with a cloud of electrons and anti-electrons and the combined energy turns out to be finite.

Physics Briefing | 7th April 2016

Searching beyond the Standard Model with photon pairs

The ATLAS Collaboration uses two selections in this search, one optimised for Higgs-like particles that are expected to have a strong signal compared to background with both photons in the central region of the detector (the “spin-0” selection) and a second optimised for graviton-like particles (the “spin-2” selection) which often have at least one photon close to the LHC proton beam axis.

Physics Briefing | 22nd March 2016

Chasing after elusive B meson decays into muons

Almost four years following the discovery of the Higgs boson, LHC experiments are now more than ever exploring the possibility of new particles and new effects beyond the Standard Model.

Physics Briefing | 22nd March 2016

Are there more Higgs bosons?

The results presented by the ATLAS collaboration during the Moriond Electroweak 2016 conference set new limits on a potential extended Higgs sector.

Physics Briefing | 22nd March 2016

New insight into the proton-proton ridge

The new results confirm that the ridges in proton-proton, proton-nucleus, and nucleus-nucleus collisions have a similar origin. The results also show that the observed weak dependence on the numbers of charged particles and the centre-of-mass energy should provide strong constraints on the mechanism responsible for producing the ridge in proton-proton, and, maybe, proton-nucleus collisions.

Physics Briefing | 2nd October 2015

Devouring dark matter theories

Most of the matter in the universe is made not of stuff we understand, but of invisible “dark matter” particles. We have yet to observe these mysterious particles on Earth, presumably because they interact so weakly with normal matter. The high energy collisions in the Large Hadron Collider provide our best current hope of making dark matter particles, and thus giving us a better understanding what most of the universe is made of.

Physics Briefing | 24th August 2015

Probing inside the proton

W and Z bosons are the massive carriers of the weak force, responsible for radioactive decays. These bosons also couple closely to the Higgs boson. W and Z bosons are produced at a large rate in proton-proton collisions at the LHC, where ATLAS physicists have now measured the rates for W and Z boson production using 13 TeV proton-proton collisions

Physics Briefing | 17th August 2015

Measuring the way protons interact at 13 TeV

One of the most basic quantities in particle physics, the rate at which protons scatter off of one another (the cross section), cannot be calculated from the theory of strong interactions, quantum chromodynamics. It must instead be measured, and those measurements can then be used to tune the numerical models of LHC proton–proton collisions.

Physics Briefing | 17th August 2015

ATLAS ready to “boost” Run 2 physics

A new set of techniques is being used to identify highly energetic top quarks, W and Z bosons, and Higgs bosons decaying to quarks and, ultimately, to hadrons measured in ATLAS. Signatures of these “boosted” Standard Model particles are particularly useful when searching for massive new particles and measuring processes at high energies.

Physics Briefing | 12th August 2015

Top quarks in Run 2 are spot on

With a precision of just under 14% − currently dominated by our ability to understand how many proton-proton collisions have occurred at ATLAS (i.e. luminosity) − this measurement is able to confirm that quantum chromodynamics, the theory of the strong interaction, still seems to be going strong!

Physics Briefing | 27th July 2015

Of mesons and bosons

ATLAS is ready for detailed physics studies. The experiment used early data collected from the LHC’s Run 2 to calibrate its detectors. Measurements of the production and leptonic decay of certain particle resonances have shown that the detectors and software are working as expected.

Physics Briefing | 24th July 2015