The Upgrade of the CMS Inner Tracker for HL-LHC

Abstract

During the Long Shutdown (LS) from 2024 to 2026 the Large Hadron Collider (LHC) will be upgraded in order to provide a tenfold increase of the data rate to the experiments. This will enhance the sensitivity of the experiments to possible unexplored rare processes and to allow for precision measurements of known processes, in particular of the properties of the Higgs Boson which was discovered in 2012. This accelerator upgrade project is called High-Luminosity LHC (HL-LHC). The entire silicon tracker of the Compact Muon Solenoid (CMS) experiment will be replaced for the HL-LHC with a new detector featuring increased radiation hardness during the collection of above 3000 fb −1 of integrated luminosity and capability to handle the higher data rate at an instantaneous luminosity of 10 35 cm −2 s −1 and longer trigger latency of 12.5 µs. The Inner Tracker will be exposed to radiation levels up to a non ionizing energy loss equivalent to 2.3 × 10 16 n eq /cm 2 and an accumulated ionizing dose of 1.2 Grad, requiring advanced technologies and novel solutions among others for the readout and powering electronics. The new detector will also feature extended pseudo-rapidity η coverage with a tracking volume up to η = 4. The High-Luminosity upgrade of the CMS silicon pixel detector is reviewed in this paper. The novel features of the detector layout and electronics system are discussed, and the expected performance is summarized.

Prototype Module Construction for the High Luminosity Upgrade of the CMS Pixel Detector

“…The internal plane is dedicated to conducting the return current between the connectors. Power simulations showed that this design ensures a power loss over the HDI at nominal current of 5 A for four chip modules of less than 200 mW per layer [7]. This will be further decreased in a revised design, currently in production.…”

“…It consists of a pixelated sensor in Planar Pixel or 3D Silicon technology, which is bump-bonded to two or four RD53 readout chips. Powering and readout signals are routed via the High Density Interconnect (HDI), a flex PCB glued to the sensor and wirebonded to the chips [7]. The powering current enters the module via the pigtail, is distributed in parallel to the readout chips and then exits to the next module via the rear-end FCP connector.…”

Determining the lifetime of long-lived particles at the HL-LHC

“…We demand that both the electrons coming from the decay of the long-lived particle X have transverse momentum p T > 20 GeV and, in order to illustrate one key difference between the previous LHC runs and the HL-LHC, we impose two alternative pseudorapidity cuts, namely |η| < 2.4 (previous Runs) or |η| < 4.0 (HL-LHC) [101]. The samples with only the p T and η cuts applied will be referred to as "basic cuts" (BC).…”

Serial Powering for the Tracker Phase-2 Upgrade

“…In the past, extensive tests have been done with single RD53A chips and dedicated Shunt-LDO test chips, which demonstrated the robustness and reliability on a chip level [5]. At the same time, CMS specific developments have been ongoing and a first prototype module that hosts four RD53A chips has been designed [6]. A detailed description of the prototype module and its construction…”