Editing UA2 experiment (section)

===Upgrades of the detector===
The 1985-1987 upgrade of the detector was aimed at two aspects: full calorimeter coverage and better electron identification at lower transverse momenta.<ref name=Jenni>{{cite book |last1=Froidevaux |first1=D. |last2=Jenni |first2=P. |year=1989 |chapter=Physics at the Improved CERN ppbar Collider |editor1-last=Altarelli |editor1-first=G. |editor2-last=Di Lella |editor2-first=Luigi |title=Proton-Antiproton Collider Physics |series=Advanced Series on Directions in High Energy Physics |volume=4 |publisher=World Scientific Publishing}}</ref> The first aspect was addressed by replacing the end-caps with new calorimeters that covered the regions 6°-40° with respect to the beam direction, thereby hermetically sealing the detector. The end-cap calorimeters consisted of lead/[[scintillator]] samplings for the electromagnetic part, and iron/scintillator for the hadronic part.<ref name=Jenni/> The performance and granularity of the new calorimeters were set to match the central calorimeter, which was of importance for the triggering system.

The electron identification was improved by the use of a completely new central tracking detector assembly, partly consisting of a pioneering silicone-pad detector. In 1989, the collaboration pushed this concept even further by developing a Silicon Pad Detector (SPD) with finer pad segmentation to be placed directly around the collision region beam pipe.<ref name=Tech>{{cite book |chapter-url=https://cds.cern.ch/record/2219700?ln=fr |last1=Gößling |first1=Claus |last2=Jarron |first2=Pierre|date=2017  |chapter=A Novel Particle Detector for UA2: The Power of Silicon |title=Technology Meets Research: 60 years of CERN Technology - Selected Highlights |publisher= World Scientific}}</ref> This detector was built as a cylinder, closely surrounding the beam pipe. The detector had to fit into the available space of less than 1&nbsp;cm. It was therefore necessary to miniaturize the components of the detector. This was achieved with two brand new technologies: the silicon sensor and the [[Application Specific Integrated Circuit]] (ASIC). Existing electronics were too bulky, and therefore a novel ASIC had to be developed. This was the first silicon tracker adapted to a collider experiment, a technology prior to the present silicon detectors.<ref name=Tech/>