In 2027 the Large Hadron Collider (LHC) at CERN will enter a high luminosity phase, deliver- ing 3000 fb 1 over the course of ten years. The High Luminosity LHC (HL-LHC) will increase the instantaneous luminosity delivered by a factor of 5 compared to the current operation pe- riod. This will impose significant technical challenges on all aspects of the ATLAS detector but particularly the Inner Detector, trigger, and data acquisition systems. In addition, many of the components of the Inner Detector are reaching the end of their designed lifetime and will need to be exchanged. As such, the Inner Detector will be entirely replaced by an all silicon tracker, known as the Inner Tracker (ITk). The layout of the Pixel and strip detectors will be optimised for the upgrade and will extend their forward coverage. To reduce the per-pixel hit rate and explore novel techniques for deal- ing with the conditions in HL-LHC, an inter-experiment collaboration called RD53 has been formed. RD53 is tasked with producing a front-end readout chip to be used as part of hybrid Pixel detectors that can deal with the high multiplicity environment in the HL-LHC. A silicon sensor, which makes up the other half of the hybrid Pixel detector, must also be designed to cope with the high fluences in HL-LHC. Significant damage will be caused by non- ionising energy loss in the sensor over its lifetime. This damage must be incorporated into the detector simulation both to predict the detector performance at specific conditions and to understand the e↵ects of radiation damage on data taking. The implementation of radiation damage in the ATLAS simulation framework is discussed in this thesis. Collisions produced by the HL-LHC also presents a challenge for the current track reconstruc- tion software. High luminosity is obtained, in part, by increasing the number of interactions per bunch crossing, which in turn increases the time taken for track reconstruction. Various ap- proaches to circumvent the strain on projected resources are being explored, including porting existing algorithms to parallel architectures. A popular algorithm used in track reconstruction, the Kalman filter, has been implemented in a neuromorphic architecture: IBM’s TrueNorth. The limits of using such an architecture for tracking, as well as how its performance compares to a non-spiking Kalman filter implementation, are explored in this thesis.

No description available.

Chiral Perturbation Theory (ChPT) is a tool for studying the strong interaction at low energies. The Perturbation theory is developed around the limit where the light quarks, u,d,s are approximated to be massless. In this approximation the isospin symmetry, one of the main features of the strong interaction, is fulfilled automatically. The study of the light quark masses and isospin violation can be done with the η'→πππ and η'→ηππ decay channels by analyzing the kinematic distribution using so-called Dalitz plots. A Dalitz plot analysis of the η'→ηπ+π- decay mode is conducted by the BESIII collaboration. The unbinned maximum likelihood method is used to fit the parameters that describe the Dalitz plot distribution. In this fit a polynomial expansion of the matrix element squared is used. However, in order to study light quark masses, it is better to use a parameterization which includes the description of the final-state interaction based on a dispersion relation. Hence, it is desirable to use a representation of the Dalitz plot as a two-dimensional histogram with acceptance corrected data as input to extract the substraction constants. Therefore, the goal of this thesis is to make a consistency check between the unbinned and binned representation of the data. In this thesis Monte Carlo data of η'→ηπ+π- decay channel is generated based on the BESIII. An unbinned maximum likelihood fit is performed to find the Dalitz plot parameters repeating the BESIII analysis method. The Monte Carlo data is then used for a binned maximum likelihood and a χ2 fit. Finally, the prepared binned experimental acceptance corrected data from BESIII is used to fit the Dalitz plot parameters using the same statistical methods. The results based on the binned maximum likelihood and the χ2 methods are consistent with the fit using the unbinned maximum likelihood method applied in the original BESIII publication.

Neutron-rich rare-earth nuclei around the maximum of collectivity are predicted to exist with an extremely stable intrinsic configuration in their ground-state structure. Due to the high degree of axial symmetry and large deformation, these nuclei are also excellent candidates for having long-lived high-K isomers. The present work concerns a study of the structure of the yrast bands and a search for isomers in the neutron-rich 68Er isotopes. Excited states of 68Er isotopes were populated via multi-nucleon transfer reactions. A 859 MeV 136Xe-beam was used to bombard a 170Er-target. The experimental setup consisted of the high-resolution γ-ray spectrometer AGATA coupled to the heavy-ion magnetic spectrometer PRISMA. The experiment collected 2 TB of useful data corresponding to 3 days of effective beam time. Beam-like fragments were identified by the PRISMA specrometer placed at the grazing angle of 44 degrees. PRISMA allows for Z, A and q identification as well as TOF and velocity vector determination. This is required for the Doppler correction of the emitted γ rays detected in time coincidence with AGATA. A good Z and very clean A separation has been achieved in PRISMA. Making use of two-body kinematics, Doppler corrected γ-ray spectra for target-like fragments were obtained as well. Due to the novel techniques of PSA and γ-ray tracking, AGATA provided high-quality γ-ray spectra for both beam-like xenon and target-like erbium isotopes. Known yrast bands and isomeric states in neutron-rich erbium isotopes were observed. A candidate for the decay of an isomeric state with Eγ=184 keV  in 173Er, which has no previously known excited states, was identified.

This Master's thesis investigates a method to measure atomic nuclei with record precision using muonic atom X-ray spectroscopy. In particular, 6Li is measured experimentally. The method used is independent from the previous most precise measurement of the 6Li nuclear charge radius which uses electron scattering. Measuring low-Z elements using muonic X-ray transitions requires excellent detectors which have so far been mostly optimised for higher energies. This project investigates methods to reach precision requirements for low-Z elements which can yield insight into nuclear structure models, and uses a Silicon Drift Detector (SDD) which is here characterised in detail and found to allow for significantly improved results over previous attempts. So far, the SDD and developed calibration scheme demonstrates a 3.7 eV precision compared to the target 0.5 eV. It appears to be limited by detector resolution, which also makes curve fitting difficult for complex line structures. A new method for generating calibration lines, X-ray fluorescence, is tested and shows good promise for future use. The planned use of a Metallic Magnetic Microcalorimeter will potentially improve results significantly, having a much-improved resolution over SDD's. Preliminary experimental results find ΔEµLi-6, 2p-1s = 18780.6 ± 15.7 eV, which is a factor of 4 improvement over the previous best measurement of this transition and the world's most precise measurement to date. While the uncertainty is larger than seen in designated calibration runs, it demonstrates the ability to perform high-precision muonic atom spectroscopy. With new detector technologies, this thesis finds no immediate obstacles to the target 0.5 eV precision.

A fundamental assumption of our universe has been that equal amounts of matter and antimatter were created during the Big Bang. Since the world we live in is made entirely of matter, one either needs to question this assumption, or explain how matter was enriched with respect to antimatter. This is a puzzle that scientists all over the world are trying to solve. Particle accelerator experiments like Belle II in Tsukuba, Japan, enable precision studies of the heavier siblings of protons, for example charmed baryons. Since these baryons are unstable, they offer a unique tool to understand the matter-antimatter-asymmetry of the universe: by comparing the decay-patterns of the baryons and antibaryons, we look for tiny differences in the interactions that, if they exist, can have led to the matter-antimatter imbalance. The project aims to examine the capacity of the Belle II generator, which is a crucial part of analysis in experimental particle physics. The aim of this project is also to develop a toolkit for estimating decay-parameters from baryon decay distributions: one single-step process and one multi-step process, and compare statistical properties of the estimators in order to see which one yields a more precise estimation.

No description available.

The aim of this thesis is to examine the hard $S$-matrix for QED and QCD, due to Hannesdottir and Schwartz [1], both recreating known results, and finding new results in lower dimensions. Electrons by themselves are not gauge invariant, and in the massless limit do not give finite $S$-matrix elements for individual processes; one needs to add together seemingly arbitrary combinations of diagrams in order to be able to calculate the scattering cross-section. One remedy is to exchange the bare electron for a dressed state, or equivalently to include the dressing in the $S$-matrix itself. This gives rise to a formalism in which one needs only consider time cuts of an individual diagram in order to find finite $S$-matrix elements. The main result of this thesis is the examination of the results which are found by Hannesdottir and Schwartz in a model system of fewer dimensions. This may be of use for toy model calculations in QCD, where 2+1-dimensional QED better models certain phenomena than does 3+1-dimensional QED.

This thesis presents a search for the supersymmetric partner of the top quark in the final state with one lepton. The search focuses especially in the region of the parameter space where the 2-body decay dominates. The analysis is performed using LHC full Run 2 data at √s = 13 TeV as recorded by the ATLAS detector. No significant excess above the backgrounds is observed, and 95% confidence level exclusion limits are calculated in the stop-neutralino mass plane. Stops are excluded up to 1200 GeV in the low neutralino mass scenario of below 400 GeV. The Tile Calorimeter is part of the ATLAS calorimeter system whose main task is to measure the energy of hadrons. A performance study is conducted on the Tile Calorimeter using muons from W boson decay originating from proton-proton collisions. Each calorimeter cell response is measure in data and compared with detector simulation.  The azimuthal cell response uniformity is also investigated using a likelihood method. Overall, a good data to detector simulation agreement and azimuthal uniformity is observed which shows well-calibrated cells and uniform responses among the calorimeter modules.

This thesis studies CP violation in the decay of the Ξ− hyperon, also known as the cascade baryon, which decays in the sequence Ξ− → Λπ− → pπ−π−. A difference between the angular distribution of this decay sequence and the angular distribution of the charge conjugate decay sequence ͞Ξ+ →͞Λπ+ → ͞pπ+π+, after taking into account the inversion of the momenta due to the parity operation, is indicative of CP violation. The decay sequence is described by three asymmetry parameters: αΞ, αΛ and φΞ, while the charge conjugate decay's sequence is described by: ͞αΞ, ͞αΛ and ͞φΞ. A measure of CP violation is given by the CP violating observables: AΞ, AΛ and ΦΞ. The aim of this thesis is to study how the normalised statistical uncertainties in the asymmetry parameters and in the CP violating observables depend on the magnitude of the polarisation vector (polarisation) of the cascade and the anticascade. This was done by simulating 1.0×107 Ξ− → Λπ− → pπ−π− and  ͞Ξ+ →͞Λπ+ → ͞pπ+π+ decays for different values of polarisation of the cascades using Monte Carlo, and then utilising maximum likelihood estimation and error propagation to estimate the uncertainties in the parameters and in the observables. It was shown using the methods of this thesis that the normalised statistical uncertainties in the asymmetry parameters and the CP violating observables decreased whenever the polarisation was increased, although with diminishing returns. In the region of 10% − 50% polarisation, the decrease in the uncertainties was substantial. An increase from 10% to 50% polarisation lowered all of the uncertainties by 76% − 80%. In the region of 50% − 100% polarisation, the decrease in the uncertainties was slightly less. An increase from 50% to 100% polarisation lowered the uncertainties in αΞ,  ͞αΞ and AΞ by roughly 33%, in αΛ,  ͞αΛ and AΛ by roughly 40%, and in φΞ,  ͞φΞ and ΦΞ it went down by 53%. It was also shown that, if one were to produce 60% polarised cascades and use the method of this thesis, it would require a sample of 1.1×1011 − 1.3×1011 Ξ− → Λπ− → pπ−π− and  ͞Ξ+ →͞Λπ+ → ͞pπ+π+ decays to reach the precision in the observables of the order given by the Standard Model. However, if one wished to match the uncertainty given by the most recent and best measurement of the observables, using 60% polarised cascades, one would only need a sample of 5.7×104 − 8.6×104 for each decay sequence.