Editing ATLAS experiment (section)

====Higgs boson====
[[File:Higgs production gg qq.png|thumb|Schematics, called [[Feynman diagram]]s show the main ways that the Standard Model Higgs boson can be produced from colliding protons at the LHC.]]

One of the most important goals of ATLAS was to investigate a missing piece of the Standard Model, the [[Higgs boson]].<ref name=fact_sheets/><ref name="TPintro">{{cite book |year=1994| title= ATLAS Technical Proposal| chapter=Introduction and Overview| publisher=CERN| chapter-url=http://atlas.web.cern.ch/Atlas/TP/NEW/HTML/tp9new/node4.html#SECTION00400000000000000000}}</ref>  The [[Higgs mechanism]], which includes the Higgs boson, gives mass to elementary particles, leading to differences between the [[weak force]] and [[electromagnetism]] by giving the [[W and Z bosons]] mass while leaving the [[photon]] massless.

On July 4, 2012, ATLAS — together with CMS, its sister experiment at the LHC — reported evidence for the existence of a particle consistent with the Higgs boson at a confidence level of 5 [[Standard deviation|sigma]],<ref name="Higgs2012" /> with a mass around 125 GeV, or 133 times the proton mass. This new "Higgs-like" particle was detected by its decay into two [[photon]]s (<math>H\rightarrow\gamma\gamma </math>) and its decay to four [[lepton]]s (<math>H\rightarrow ZZ^*\rightarrow 4l</math> and <math>H\rightarrow WW^*\rightarrow e\nu\mu\nu</math>).

In March 2013, following the updated results from ATLAS and CMS, CERN announced that the newly discovered particle was indeed a Higgs boson. The experiments were also able to show that the properties of the particle as well as the ways it interacts with other particles were well-matched with those of a Higgs boson, which is expected to have [[Spin (physics)|spin]] 0 and positive [[Parity (physics)|parity]]. Analysis of more properties of the particle and data collected in 2015 and 2016 confirmed this further.<ref name="Higgs2015">{{cite web|url=http://press.cern/press-releases/2015/09/atlas-and-cms-experiments-shed-light-higgs-properties|title=ATLAS and CMS experiments shed light on Higgs properties|access-date=2016-11-23}}</ref>

In October 2013, two of the theoretical physicists who predicted the existence of the Standard Model Higgs boson, [[Peter Higgs]] and [[François Englert]], were awarded the [[Nobel Prize in Physics]].