Reconstruction of Heavy Flavour Jets for Precision Higgs Physics Studies

Abstract

Precision measurements of the 125-GeV Higgs boson are at the core of the physics program of future electron-positron colliders. Thereby, decays of the Higgs boson into heavy flavour jets play important roles at lepton colliders: decays into b-quarks because they are expected to be the most frequently occurring ones, decays into c-quarks because they are extremely challenging to measure at hadron colliders. Several important measurements would thus profit significantly from further improvements of heavy flavour jet reconstruction and identification.\\ The main goal of this PhD thesis the development of reconstruction algorithms for heavy flavour jets which, for the first time, fully exploit all the information offered by the highly-granular, particle flow optimised detector concepts foreseen for future $e^{+}e^{-}$ colliders. This includes e.g.\ particle identification via $dE/dx$, cluster shapes, and time-of-flight, identification of leptons in jets, reconstruction of exclusive decay chains including "invisible" neutrinos from semi-leptonic decays, as well as kinematic fitting.\\ Benchmarking the developed tools on $e^{+}e^{-}\rightarrow ZH/ZZ\rightarrow\mu^{+}\mu^{-}b\bar{b}$ events at $\sqrt{s}=250\;\mathrm{GeV}$ in full, Geant4-based simulation of the ILD detector concept shows a significant improvement of the $m_{b\bar{b}}$ reconstruction.