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@PHDTHESIS{Gautam:637693,
author = {Gautam, Kunal},
othercontributors = {Blekman, Freya},
title = {{P}recision {M}easurement of {S}trange {Q}uark {A}symmetry
and {M}onolithic {P}ixel {S}ensors for {V}ertexing at the
{FCC}-ee},
school = {University of Brussels and University of Zurich},
type = {Dissertation},
address = {Hamburg},
publisher = {Verlag Deutsches Elektronen-Synchrotron DESY},
reportid = {PUBDB-2025-03896, DESY-THESIS-2025-017},
series = {DESY-THESIS},
pages = {199},
year = {2025},
note = {Dissertation, University of Brussels and University of
Zurich, 2025},
abstract = {Future e+e− colliders, such as the FCC-ee, aim to test
the Standard Model to the ultimateprecision. This requires
synergistic progress in detector technology and data
analysis techniques.This thesis comprehensively presents the
interlinked efforts targeting these goals.Jet flavour
identification algorithms play a crucial role in maximally
exploiting the physicspotential of the FCC-ee, particularly
in the Higgs and electroweak sectors. The
DeepJet-Transformer algorithm, exploiting a
transformer-based neural network that is substantiallyfaster
to train than state-of-the-art graph neural networks,
combines particle-flow reconstruc-tion with advanced vertex
reconstruction and hadron particle identification. Beyond an
excellentb- and c-jet discrimination, an s-jet tagging
efficiency of $40\%$ can be achieved with a $10\%$
ud-jetbackground efficiency. The impact of K±/π±
discrimination with varying efficiencies and inclu-sion of
reconstructed V0s for strange tagging performance is shown.
Similarly, the importanceof charged jet constituents and
reconstructed secondary vertices for bottom and charm
taggingis presented. The bottom and charm tagging
efficiencies were largely uniform over the entiremomentum
and polar angle range of interest. However, the strange
tagging efficiency showed adependence on the K± and V0
multiplicities in different momentum regimes.A 5σ discovery
significance can be achieved while isolating Z → s¯s
events from the exclusivedecays of the Z boson with an
integrated luminosity of 60 nb−1 of e+e− collisions at
√s =91.2 GeV, corresponding to less than a second of the
FCC-ee run plan at the Z boson resonance.The improved
strange tagging performance opens new avenues for extracting
quark-specificasymmetries, such as the forward-backward
asymmetry (AFB). Using advanced neural network-based strange
tagging and quark-antiquark jet separation with jet charge,
the AFB measurementin the strange decay channel of the Z
boson is possible with an absolute statistical precisionof
2.6 · 10−6 at the FCC-ee, considering a luminosity of 125
ab−1 at the Z resonance. Thecorresponding sin2 θW value
can be measured with an absolute statistical precision of
4.6 · 10−6.To support these improvements, ultra-thin,
high-resolution, and robust vertex detectors areessential.
Recent advancements in the use of ultra-light monolithic
active pixel sensors (MAPS),developed in the 65 nm imaging
process, for the ALICE ITS3 project by an international
consor-tium of the ALICE collaboration and the CERN EP
$R\&D$ project envision drastic improvementsin vertexing
performance. Process modification is introduced by adding a
deep low-dose n-typelayer, which aids in the depletion of
full sensor volume by extending the depletion region
later-ally while keeping a low sensor capacitance. It leads
to faster charge collection and reduction incharge shared
with neighbouring pixels, thus improving the detection
efficiency.Pixel response calibration and energy resolution
measurements performed with the 55Fe ra-dioactive source in
the controlled laboratory environment are presented. Four
variants of pixelgeometry were tested with a small-scale
analogue prototype, APTS, all showing over $99\%$
chargecollection efficiency for a small reverse bias voltage
of 1.2 V. The impact of geometry variationon detection
efficiency, spatial resolution, and radiation tolerance is
highlighted. In-pixel effi-ciency studies show that the loss
of efficiency at high thresholds is primarily concentrated
at theedges and corners of the pixels. APTS shows sub-3 μm
spatial resolution and > $99\%$ detectionefficiency, even
under moderate irradiation, satisfying the stringent
requirements of ALICE andfuture collider
environments.Together, these developments highlight the
integrated advancements in detector design, re-construction
algorithms, and physics potential, strengthening the next
generation of precisionmeasurements at the FCC-ee and
beyond.},
cin = {CMS},
cid = {I:(DE-H253)CMS-20120731},
pnm = {611 - Fundamental Particles and Forces (POF4-611)},
pid = {G:(DE-HGF)POF4-611},
experiment = {EXP:(DE-H253)LHC-Exp-CMS-20150101},
typ = {PUB:(DE-HGF)3 / PUB:(DE-HGF)11},
doi = {10.3204/PUBDB-2025-03896},
url = {https://bib-pubdb1.desy.de/record/637693},
}