Performance Requirements for the Phase-2 Tracker Upgrades for ATLAS and CMS

Duccio Abbaneo, R. Frühwirth, E. Brondolin, B. Kolbinger, W. Waltenberger
2016 EPJ Web of Conferences  
The High-Luminosity operation of the LHC poses unprecedented challenges for the design of the upgraded trackers of ATLAS [1] and CMS [2] . The stringent requirements imposed by the high particle density and integrated fluence reduce the phase-space of valid technical solutions, inducing both collaborations to design "all-silicon" trackers. On the other hand constraints and requirements coming for the rest of the detector lead to some different choices, especially for the outer trackers. The
more » ... r trackers. The main requirements for the two tracking systems are reviewed, discussing the implications for the detector designs and layout, and explaining why some of the technical choices remain different in the two experiments. To conclude, some expected performance figures for the two tracking systems are presented. 1 Requirements for the High-Luminosity LHC tracking systems 1.1 Requirements from higher particle rates A major challenge for the design of the HL-LHC trackers is the target integrated luminosity of 3000 fb −1 , which translates to unprecedented requirements in terms of radiation tolerance, particularly difficult to meet for sensors and on-detector electronics. The outer trackers will have to operate with unspoiled performance throughout the high luminosity program, planned for the decade 2026 − 2035, while it is conceivable that the inner parts of the pixel detectors could be replaced during a long shutdown, if the radiation tolerance requirements cannot be fulfilled. ATLAS and CMS have performed detailed FLUKA [3] simulations to estimate the radiation exposure of the different detector regions, obtaining consistent results (Figure 1) . The estimated levels are about one order of magnitude higher compared to the requirements that were used for the design of the existing trackers [4][5][6][7], reaching levels of 10 16 particles per cm 2 in the innermost pixel regions. The particle fluence depends essentially on r (the distance from the beam axis), while the variation with z (the distance from the nominal average collision point, along the beam axis) is very moderate. When translating such radiation levels into requirements for the design of the tracking subdetectors, it should be noted that the boundary between the outer tracker and the pixel detector is located at a radius of about 350 mm in ATLAS and 200 mm in CMS. Furthermore, in the present tracker upgrade layouts the first pixel layer is located at 39 mm in ATLAS and at 29 mm in CMS, which translates to a e-mail:
doi:10.1051/epjconf/201612700002 fatcat:uzawmdxn2bcd7m5jvyczmyxvma