The Upgraded Outer Tracker for the CMS Detector at the High Luminosity LHC, and Search for Composite Standard Model Dark Matter with CMS at the LHC

The Standard Model of particle physics describes the interactions between particles at the smallest known scale. The Standard Model has passed many tests with flying colours, but several observations, such as the need for dark matter, do not find an explanation in this framework. The Large Hadron Collider (LHC) at CERN is an excellent tool to study the Standard Model and to try and find answers to the open questions. The LHC collides protons resulting in a center of mass energy of 13~TeV, the highest energies ever attained at a particle collider. This enables physicists to study matter at an energy scale which is normally not accessible and which reflects the energy density in our Universe a fraction of a second after the Big Bang. At one of the four interaction points along the LHC, the Compact Muon Solenoid (CMS) experiment is located. This general purpose experiment is designed to give an as good as possible measurement of the kinematic properties of the particles produced in a collision. CMS does this by using several subdetectors, one of which is the tracking system. The CMS tracker is based on silicon technology and consists of a pixel and a strip detector, designed to reconstruct the tracks of charged particles. The strip detector has been taking data since the start of the operation of the LHC in 2010 and will continue to do so until 2024. During the 2025-2027 Long Shutdown of the LHC, the accelerator complex will be upgraded to start the High Luminosity LHC (HL-LHC) phase at the end of 2027, which will provide the experiments with higher luminosities by increasing the number of proton-proton collisions per bunch crossing (pileup). In order to keep tracking performance at pre-HL-LHC levels in this harsher HL-LHC environment, the strip tracker will be replaced by an Outer Tracker, consisting of pixel-strip (PS) and strip-strip (2S) modules. These modules have local track reconstruction logic. The output of this logic is used as input to the L1 trigger system. This thesis consists of a hardware part, focussing on the testing of Outer Tracker prototypes, and a search for new physics using the data collected by the CMS experiment. $\\$ $\textit{The Upgraded Outer Tracker for the CMS Detector at the High Luminosity LHC: }$ $\\$Over the past years, Outer Tracker prototype ASICs and modules have become available. These require a dedicated test bench for characterization. This thesis discusses in detail the Phase-2 Outer Tracker and the structure and scope of the firmware project ($\mu$DTC) set up to read out ASIC and module prototypes of this new detector. The test bench is designed to test both 2S and PS modules and components. Several tests, to which the author contributed, are presented, going from bench-top testing of single ASICs, through radiation hardness testing of these chips and operating module prototypes in test beams. $\\ \textit{Search for Composite Standard Model Dark Matter with CMS at the LHC:}$ $\\$ The Sexaquark (S), composed of uuddss quarks, is a hypothetical particle that was proposed to be stable and a potential dark matter candidate. $\bar{S}$ particles could be produced in the proton-proton collision and could subsequently annihilate on a neutron in the beampipe or detector material. This annihilation could result in a $\mathrm{K_S^0} + \bar{\Lambda}^0)]$ which in turn can decay to charged products which are reconstructable with the CMS tracker. This is the signal used in this thesis to look for the $\bar{S}$ in the CMS 2016 dataset by reconstructing the $\bar{S}$ kinematic properties and its annihilation vertex. The difficulties of reconstructing such a low momentum, displaced and off-pointing signature with the default CMS reconstruction algorithms will be studied and a first-ever limit on the $[\sigma(\mathrm{p+p} \rightarrow \mathrm{\bar{S}}) \times \sigma(\mathrm{\bar{S}} + \mathrm{n} \rightarrow \mathrm{K_S^0} + \bar{\Lambda}^0)]$ cross section will be presented

Characterization of the first prototype of the Silicon-Strip readout ASIC (SSA) for the CMS Outer-Tracker phase-2 upgrade

The silicon strip readout ASIC (SSA) for the CMS Outer Tracker PS module was prototyped in a $65\,nm$ CMOS technology and characterized utilizing a custom made test bench based on the FC7 $\mu$TCA FPGA card. The ASIC has been evaluated and characterised under different working temperatures and radiation levels up to $200\,Mrad$. Measurements show a front-end gain between $35$ and $54\,mV/fC$ and an average noise of $<330\,e^-$, meeting the specification of noise performance. The measured peaking time for an injected charge between $0.5\,fC$ and $8\,fC$ is $\approx19\,ns$ allowing to detect consecutive particle events in combination with the zero dead-cycle binary readout. The embedded trimming circuit allows to obtain a measured threshold spread smaller than $55\,e^-$ between channels. The measured power consumption is $\approx60\,mW$ and thus within the strict power budget of the PS modules. The performance characterization results and radiation tolerance test results of the first SSA silicon prototype are presented

Characterization of the MPA prototype, a 65 nm pixel readout ASIC with on-chip quick transverse momentum discrimination capabilities

The first prototype of the full-size, full-functionality Macro Pixel ASIC has been produced in a 65~nm technology employing radiation tolerant techniques. It is a pixel readout ASIC designed for the Phase-2 upgrade of the CMS Outer Tracker detector. It features novel on-chip particle discrimination capabilities allowing for real-time event-driven readout of high transverse momentum particles at a 40~MHz rate. This data flow is complemented with a zero suppressed triggered readout data path for the readout of full events at a maximum rate of 1~MHz. This contribution presents the functional and performance evaluation results obtained from silicon prototypes

Quality control considerations for the development of the front end hybrid circuits for the CMS Outer Tracker upgrade

The upgrade of the CMS Outer Tracker for the HL-LHC requires the design of new double-sensor modules. They contain two high-density front end hybrid circuits, equipped with flip-chip ASICs, passives and mechanical structures. First prototype hybrids in a close-to-final form have been ordered from three manufacturers. To qualify these hybrids a test setup was built, which emulates future tracker temperature and humidity conditions, provides temporary interconnection, and implements testing features. The system was automated to minimize the testing time in view of the production phase. Failure modes, deliberately implemented in the produced hybrids, provided feedback on the system’s effectiveness

A High Throughput Production Scale Front-End Hybrid Test System for the CMS Phase-2 Tracker Upgrade

More than twenty-five thousand hybrids will be produced for the CMS Outer Tracker Phase-2 Upgrade. The hybrids are assembled with flip-chips, passives and carbon-fibre stiffeners. They will be glued to their module supports, together with powering and optical transmission hybrids, making repairs almost impossible. Due to the complexity of the hybrid circuits and the circuit assembly, production scale testing is a very important aspect. A crate-based scalable test system was designed to enable a multiplexed test of front-end hybrids. A test card was produced for the 2S hybrids and two different hybrid test cards are under development

Beam Test Performance of Prototype Silicon Detectors for the Outer Tracker for the Phase-2 Upgrade of CMS

A new CMS tracker detector will be installed for operation at the High Luminosity LHC\,(HL-LHC). This detector comprises modules with two closely spaced parallel sensor plates and front-end ASICs capable of transmitting tracking information to the CMS Level-1\,(L1) trigger at the 40\,MHz beam crossing rate. The inclusion of tracking information in the L1 trigger decision will be essential for selecting events of interest efficiently at the HL-LHC. The CMS Binary Chip\,(CBC) has been designed to read out and correlate hits from pairs of tracker sensors, forming so-called track stubs. For the first time, a prototype irradiated module and a full-sized module, both equipped with the version 2 of the CBC, have been operated in test beam facilities. The efficiency of the stub finding logic of the modules for various angles of incidence has been studied. The ability of the modules to reject tracks with transverse momentum less than $2~\mathrm{GeV}$ has been demonstrated. For modules built with irradiated sensors, no significant drop in the stub finding performance has been observed. Results from the beam tests are described in this paper