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A bstract The accurate identification of heavy-flavour jets — those which originate from bottom or charm quarks — is crucial for precision studies of the Standard Model and searches for new physics. However, assigning flavour to jets presents significant challenges, primarily due to issues with infrared and collinear (IRC) safety. This paper aims to address these challenges by evaluating recently-proposed jet algorithms designed to be IRC-safe and applicable in high-precision measurements. We compare these algorithms across benchmark heavy-flavour production processes and kinematic regimes that are relevant for LHC phenomenology. Exploiting both fixed-order calculations in QCD as well as parton shower simulations, we analyse the infrared sensitivity of these new algorithms at different stages of the event evolution and compare to flavour labelling strategies currently adopted by LHC collaborations. The results highlight that, while all algorithms lead to more robust flavour assignments compared to current techniques, they vary in performance depending on the observable and energy regime. The study lays groundwork for robust, flavour-aware jet analyses in current and future collider experiments to maximise the physics potential of experimental data by reducing discrepancies between theoretical and experimental methods.

Jet substructure observables are powerful tools to search for new physics and test theoretical descriptions of perturbative and non-perturbative processes in QCD. In heavy-ion collisions, jet substructure observables are used to elucidate the structure and dynamics of the quark-gluon plasma. One substructure observable is jet mass, which probes the virtuality of hard-scattered partons and their modified fragmentation. Additionally, generalized jet angularities allow differential measurements of the jet shower and its modification, as two parameters independently vary the weight of the jet constituents’ relative angle and transverse momentum. Previous measurements of the jet mass and jet angularities show conflicting deviations when compared with models. This thesis presents new measurements of the jet mass and jet angularities to resolve this conflict, using charged-particle tracks in pp and Pb-Pb collisions at $\\sqrt{s_\\mathrm{NN}} = 5.02$ TeV and jet resolution parameters R = 0.2 and 0.4. The results from this work are compared to ALICE measurements of heavy-flavor jets, which provide a high-powered probe of perturbative QCD at low transverse momentum. Jet angularities in jets containing a charm meson are compared to the inclusive measurements of this thesis, revealing a significant narrowing due to the QCD dead cone modifying jet fragmentation. Jet angularity results are also compared to QCD predictions using both folding and shape function corrections for nonperturbative effects. Jet grooming can be used to isolate specific splittings inside the jet fragmentation history, and ALICE measurements of the groomed-jet splitting angle and momentum fraction with soft drop and dynamical grooming are also compared to QCD predictions to test parton branching. The high-precision tracking system of ALICE enables these measurements over a broad range in transverse momentum, with a low-transverse momentum reach that is unique at the LHC.

Jet substructure observables provide powerful tools to search for new physics and test theoretical descriptions of perturbative and non-perturbative processes in QCD. In heavy-ion collisions, jet substructure observables are used to elucidate the structure and dynamics of the quark-gluon plasma. Jet mass is one such observable, which probes the virtuality of hard-scattered partons and their modified fragmentation. Additionally, generalized jet angularities provide a powerful tool for differential measurements of the jet shower and its modification, as two parameters vary the weight of the jet constituents' relative angle and \\(p_\\mathrm{T}\\). Previous measurements of the jet mass and jet angularities have shown conflicting differences in comparison with models. To clarify these results, we present new measurements of the jet mass and jet angularities using an identical jet sample. The high-precision tracking system of ALICE enables these measurements over a broad range in \\(p_\\mathrm{T}\\), with low-\\(p_\\mathrm{T}\\) reach that is unique at the LHC. We report the generalized jet mass and jet angularities using charged-particle tracks in Pb-Pb collisions at \\(\\sqrt{s_\\mathrm{NN}} = 5.02\\) TeV. Various jet angularity parameters are investigated for the jet resolution parameter \\(R = 0.2\\). Results are compared to pp collisions and theoretical models.

The accurate identification of heavy-flavour jets, those which originate from bottom or charm quarks, is crucial for precision studies of the Standard Model and searches for new physics. However, assigning flavour to jets presents significant challenges, primarily due to issues with infrared and collinear (IRC) safety. This paper aims to address these challenges by evaluating recently-proposed jet algorithms designed to be IRC-safe and applicable in high-precision measurements. We compare these algorithms across benchmark heavy-flavour production processes and kinematic regimes that are relevant for LHC phenomenology. Exploiting both fixed-order calculations in QCD as well as parton shower simulations, we analyse the infrared sensitivity of these new algorithms at different stages of the event evolution and compare to flavour-labelling strategies currently adopted by LHC collaborations. The results highlight that, while all algorithms lead to more robust flavour-assignments compared to current techniques, they vary in performance depending on the observable and energy regime. The study lays groundwork for robust, flavour-aware jet analyses in current and future collider experiments to maximise the physics potential of experimental data by reducing discrepancies between theoretical and experimental methods.