Editing UA2 experiment (section)

==History==
On 29 June 1978 the [[UA1 experiment]] was approved. Two proposals for a second detector, with the same purpose as UA1, were made the same year. On 14 December 1978, the proposal of [[Pierre Darriulat]], [[Luigi Di Lella]] and collaborators, was approved.<ref>{{cite journal |last1=Banner |first1=M|display-authors=etal |date=31 January 1978 |title=Proposal to Study Antiproton-Proton Interactions at 540 GeV CM Energy |url=https://cds.cern.ch/record/596804/files/CM-P00045649.pdf |journal=SPS Committee |access-date=24 July 2017}}</ref> Like [[UA1]], UA2 was a moveable detector, custom built around the beam pipe of the collider, which searched proton–antiproton collisions for signatures of the W and Z particles.<ref name=UA2CERN/> The UA2 experiment began operating in December 1981. The initial UA2 collaboration consisted of about 60 physicists from [[University of Bern|Bern]], CERN, [[University of Copenhagen|Copenhagen]], [[University of Paris-Sud in Orsay|Orsay]], [[University of Pavia|Pavia]] and [[University of Paris-Saclay|Saclay]].

From 1981 to 1985, the UA1 and UA2 experiments collected data corresponding to an integrated luminosity of approximately {{val|0.9|u=[[barn (unit)|pb<sup>−1</sup>]]}}. From 1985 to 1987 the Sp{{overline|p}}S was upgraded, and the [[Luminosity (scattering theory)|luminosity]] of the machine increased by a factor 10 compared to the previous performance.<ref name=Rubbia/> The UA2 sub-detectors were also upgraded, making the detector hermetic, which increased its ability to measure missing transverse energy.

The second experimental phase ran from 1987 to 1990. Groups from [[University of Cambridge|Cambridge]], [[University of Heidelberg|Heidelberg]], [[University of Milan|Milano]], [[University of Perugia|Perugia]] and [[University of Pisa|Pisa]] joined the collaboration, which grew to about 100 physicists. During this phase, UA2 accumulated data corresponding to an integrated luminosity of {{val|13.0|u=pb<sup>−1</sup>}} in three major running periods.<ref name=Jakobs>{{cite journal |last1=Jakobs |first1=Karl |year=1994 |title=The physics results of the UA2 experiment at the CERN p{{overline |p}} collider |journal=[[International Journal of Modern Physics A]] |volume=09 |issue=17 |pages=2903–2977 |doi=10.1142/S0217751X94001163|bibcode=1994IJMPA...9.2903J |url=https://cds.cern.ch/record/260845 }}</ref> After nearly ten years of operation, the UA2 experimental program stopped running at the end of 1990.