From Physics Analysis to Detector Upgrades: Search for anomalous gauge couplings and upgrades to the ATLAS Liquid Argon calorimeter

This thesis presents two complementary contributions to the ATLAS experiment at the CERN Large Hadron Collider. The first is a physics analysis of the rare pp → Wμμ reaction, aimed at probing anomalous quartic gauge couplings within an Effective Field Theory framework. Limits are set on dimension-8 operators, with the strongest sensitivity to T-type operators (OT,5 and OT,6), providing new constraints on corresponding Wilson coefficients. The 95% confidence intervals were found to be −1.3 TeV$^{−4}$ < $f_{T,5}/\Lambda^4$ < 1.3 TeV$^{−4}$ and −1.7 TeV$^{−4}$ < $f_{T,6}/\Lambda^4$ < 1.6 TeV$^{−4}$, demonstrating competitive sensitivity. Additionally, a two-dimensional likelihood scan was also performed to assess parameter correlations, producing constraints consistent with the one-dimensional confidence intervals.

The second contribution supports the Phase-II upgrade of the ATLAS Liquid Argon calorimeter electronics. High-speed optical data transmission using the Core1990 protocol was successfully demonstrated between a Field Programmable Gate Array (FPGA) device emulating the functionalities of the future digital signal processing system, and a prototype Global Event Processor (GCMv3) designed for the future trigger system. Data transfer tests achieved up to 90% bandwidth utilization, a latency of 300 ns, and zero bit errors over extended testing. All measurements are in good agreement with theoretical expectations and exceed the new requirements of the Trigger and Data AcQuisition systems.

Together, these efforts enhance both the discovery potential for new physics and the technical readiness of ATLAS for the High-Luminosity LHC era.