Physics Briefings

the density of allowed supersymmetric models before and after the ATLAS Run-1 searches

Devouring dark matter theories

24th August 2015Most 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.

Read more →
Ratio of W+ to W- boson production fiducial cross sections

Probing inside the proton

17th August 2015W 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

Read more →
The inelastic cross section, as measured in this work, versus the collision energy

Measuring the way protons interact at 13 TeV

17th August 2015One 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. 

Read more →
Rejection of quark and gluon jets for a 50% W boson selection efficiency

ATLAS ready to “boost” Run 2 physics

12th August 2015A 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.

Read more →
This new result at 13 TeV (red circle) is compared to previous results from ATLAS

Top quarks in Run 2 are spot on

27th July 2015With 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! 

Read more →
Two-particle correlations

ATLAS measurements of the ridge in proton-proton collisions at 13TeV

24th July 2015Previous studies of two-particle angular correlations in proton-proton, proton-lead, and lead-lead collisions at the LHC have provided important insight on the physics of the particle production process. On 24 July, Atlas presented new preliminary measurements of two-particle correlations...

Read more →
Lepton transverse momentum distribution from the W→ μν selection

Of mesons and bosons

24th July 2015ATLAS 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. 

Read more →

Pages