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| Home > Publications database > From Jets to Pixels: Flavour Tagging and Monolithic Pixel Sensors at the FCC-ee |
| Book/Dissertation / PhD Thesis | PUBDB-2025-03895 |
;
2025
Verlag Deutsches Elektronen-Synchrotron DESY
Hamburg
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Please use a persistent id in citations: doi:10.3204/PUBDB-2025-03895
Report No.: DESY-THESIS-2025-016
Abstract: The FCC-ee is the first stage of a two stage project which would envision a 92 km tunnelbeing used for an electron-positron collider experiment starting around 2045, and a proton-proton collider in the 2070’s. The FCC-ee offers unprecedented precision tests of the StandardModel, owing to its clean leptonic collision environment and exquisite luminosity. The preciseidentification of decay products at future colliders is instrumental to the exploitation of the fullphysics potential. In this thesis two facets of this problem are explored: jet flavour tagging andcharged particle tracking.Jet flavour tagging describes the algorithmic identification of the initiating parton fromhadronic decays. The prospect of identifying strange quark jets has emerged as a promisingavenue to study a multitude of largely unexplored processes, including Z → s¯s production andrare Higgs boson decays. DeepJetTransformer is a transformer-based multiclassifier neural net-work developed by the CMS jet tagging team at the VUB, achieving state-of-the-art performancewhile being relatively lightweight. This thesis combines DeepJetTransformer with secondary ver-texing and a novel implementation of K-short reconstruction at the FCC-ee to identify strangejets. Through the inclusion of different levels of K±/π± discrimination, strange tagging efficien-cies ranging from 31.6% to 57.8% were obtained at a u, d jet efficiency of 10%, highlighting theneed for charged Kaon discrimination at future colliders.Monolithic Active Pixel Sensors (MAPS) combine the sensing node and readout circuitry intothe same substrate, thus offering several advantages with respect to their hybrid counterparts.The Circuit Exploratoire 65 nm (CE-65), and its evolution CE-65v2, are MAPS test structuresproduced in the 65 nm TPSCo CMOS process to explore charge collection properties for avariety of configurations, including variations in pixel pitch, process modification, amplificationscheme, and matrix geometry. In this thesis the lab characterisation of the CE-65v1 and CE-65v2 chips is reported, where charge collection efficiencies of 96% were achieved for all variants.In a subsequent beam test at CERN SPS a sub 3 μm spatial resolution was obtained for Standardprocess variants, satisfying FCC-ee requirements. The characterisation of the CE-65 family ofchips has supplemented the APTS and DPTS studies in the validation of the 65 nm TPSCoprocess as a candidate technology for advanced particle detection applications, directly informingthe development of future tracking detectors
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