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The non-trivial structure of the QCD vacuum gives rise to a P and CP violating term in the QCD Lagrangian. The fact that we do not see an observable CP violation in the strong interaction despite this CP violating theta term is called the Strong CP Problem. In this thesis, we analyze an observable consequence of this theta vacuum term in the decay of the ground state neutral Sigma hyperon. Due to the SU(3) flavor symmetry, the current upper bound of the neutron electric dipole moment can be translated to an angular asymmetry in the decay distribution of the Σ0 particle. The selfanalyzing weak decay of the Λ hyperon means that any P violation in the initial Σ0 → Λγ decay will result in an asymmetry in the angular distribution of the final decay products. Studying the Sigma and anti-Sigma hyperon decays, we get an idea of C and CP violation in the decay chain. The effect of the production process of the Σ0 hyperon on the angular distribution of the final products is also worked out. A significant angular asymmetry in the decay will mean not only physics beyond the Standard Model, but also physics beyond the CP violating term in the QCD Lagrangian

Fission yields represent the probability of producing a certain nuclide in a fission event, and are important observables for fission research. For applications, accurate knowledge of the yields is fundamental at all stages of the fuel cycle of nuclear reactors, e.g., for reactivity calculations, or to estimate (spent) fuel inventory. Fission yields also help in the basic understanding of the fission process, for nucleosynthesis models, and for radioactive ion beam production. This thesis was developed in the framework of the AlFONS project, the objective of which was to measure neutron-induced fission yields of relevance for partitioning and transmutation of spent fuel. The work is performed at the IGISOL-4 facility in JYFL (University of Jyväskylä). The first part of this thesis work is dedicated to the development and characterisation of a suitable 9Be(p(30MeV),nx) neutron source for IGISOL-4. The neutron energy spectrum and the neutron yield from a 5mm thick converter were studied with Monte Carlo simulations. Two characterisation campaigns that validated the MCNPX code were also performed. At the maximum current available from the cyclotron at JYFL, a total neutron yield between 2 and 5×1012 neutrons/(sr s) can be obtained. This satisfies the design goal for studies of fission yields. The neutron source was used in the measurement of fission yields from high-energy neutron-induced fission of natU at IGISOL-4, discussed in the second part of this thesis. The fission products were online-separated with a dipole magnet. The isobars, with masses in the range A = 128-133, were identified using γ-spectroscopy. Data for the relative yields of tin and antimony, as well as isomeric yield ratios for five nuclides will be reported. The yields show trends not observed in the ENDF/B-VII.1 evaluation, and only in part confirmed by the GEF model. The final part of this thesis concerns a study of the performance of different nuclear model codes, that aim at describing the states of the fission fragments right after scission. Reproduction of experimental data serves to benchmark the models and it indicates, to some extent, how reliably the results can be extrapolated to regions where no data exist. A methodology to compare and test these models has been developed, which was implemented in the DEℓFIN code. DEℓFIN takes the excited fission fragments, defined by the model under test, and de-excites them in a standardised way using the nuclear model code TALYS. Eliminating any variability in the way the final observables are extracted helps focusing on each model's assumptions. DEℓFIN was tested on five models, and interesting features in the prompt neutron multiplicity were found for some of them. This study will promote a better understanding of the ideas used in the development of fission models.

In this master thesis a thorough analysis of data collected in an experiment performed at the JYFL accelerator laboratory in Finland using a reaction with a 47-Ti beam on a 58-Ni target is presented. The prompt emitted gamma rays from the fusion-evaporation products were detected in the gamma-ray spectrometer JUROGAM II, while the recoils were detected in the GREAT spectrometer. The main aim of this work was to use triple gamma-ray coincidences to find out if it is possible to discover new levels and transitions in proton-rich nuclides such as 103-Sn and 101-In.  A recoil triggered gamma-cube of coincident gamma rays was constructed and analyzed with the program levit8r from the Radware software package. From an intensity estimation of the data it was concluded that 102-Ag was the strongest reaction channel and emission of 3-7 particles in the fusion-evaporation reaction was favoured. By analyzing peaks in double-gated spectra of the gamma-cube, three new levels and seven new gamma-ray transitions up to an excitation energy of 8644 keV and an angular momentum of 22 h were proposed as a continuation of rotational band B3 published in a recent article on 102-Ag. From plots of the alignment of the newly proposed transitions no band crossing was observed, just a smooth continuation of the band. The efficiency of the charged particle detector, UoYTube, was deduced to be about 66% for proton detection, while the probability to detect one random proton was about 10%.

An exploratory investigation of the electron reconstruction efficiencyat the LHCb is presented. The study is done through simulations ofparticle interaction with the full LHCb detector setup, both by firingsingle particles into the detector and by generating the decay of Bmesons into J/psi K, where the J/psi decays into dileptons. PreviousLHCb analysis of the decay has shown a large yield difference betweenthe number of electron versus muon final states, around a factor offour. The kinematical dependence on the reconstruction efficiency ofthe leptons is studied and found to be non-discriminatory. Theelectronic channel loss of yield is compared to the muonic channel withthe purpose of finding in which reconstruction and selection steps theyield discrepancy factor originates. A total factor of 1.8 is found,which combined with the L0 trigger factor of 2 makes the resultcomparable to the observed factor. A large loss of yield from ageometrical selection, which requires electrons to be in the acceptanceof the electromagnetic calorimeter or in the pre-shower detector,triggers a study of the performance of electrons failing thisrequirement. The performance is determined by looking at how well theparticles are identified, using both LHCb data and simulations. Thefailing electrons are found to perform well, therefore the requirementis considered superfluous and avoiding it would increase the electronfinal state yield with around 14.5%.

The Division of Applied nuclear physics at Uppsala university, isregularly performing high-precision measurements on isomeric fissionyield ratios (IYR). Its aim is to explore the physics behind nuclearfission, in particular how angular momentum is generated. Thedepartment has developed a method to obtain the root mean square(rms) values of the primary fission fragment angular momentumdistribution (Jrms). However, several assumptions are made in themodel; thus this project aims to assess the sensitivity of the modelparameters. In particular, the focus is on assessing the mean andwidth of the excitation energy distribution, as well as thecorrelation between the excitation energy and the angular momentum.The task is to implement a method that builds upon the previousmodel. The method that was implemented is based on random sampling,which randomises values of the parameters in a specific rangedepending on the type of distribution.Three types of distributions (Normal, Rayleigh and Poisson) of theexcitation energy were tested, and it seemed to have little effecton the system. The fact that the distributions are symmetric orantisymmetric seemed to have negligible impact.The nucleus that was studied was 134I after the fission process withparent nucleus 235U in the thermal energy range. The IYR was plottedagainst four parameters: Jrms, a proportionality constant (A)between the energy and angular momentum, the intrinsic energy (Eint)and the spread of the energy (E).Their mean values and spread wasacquired from a fission simulations software called GEF. Using theseas inputs to another software TALYS, one can acquire the isomericyield ratios (IYR) for the nucleus with different neutron channels.Jrms has the most impact, and had a clear interval which gave a IYRvalue close to experiments. The three other parameters showed noclear correlation which results in the conclusion: the IYR says verylittle about the fragments excitation energy but quite a lot aboutits angular momentum in the case of 134I with the assumptions made.

The purpose of this project is to study the plasma delay time phenomenon in preparation for the construction of the VERDI spectrometer. To accomplish this, simulations of the spontaneous fissioning process of Cf-252 were created using the fission code GEF, as well as MATLAB. GEF has produced one million fission events, from which the time of flight and kinetic energy of each fission fragment have been calculated with classical mechanics, to replicate the experiment. To imitate the plasma delay time phenomenon, three different models, found in the literature, have been compared. Accounting for other realistic resolution effects and using the first model as the plasma delay time phenomenon, the absolute errors of the mass-yields reaches up to 4 u, whereas the second and third model display absolute errors up to 3 u. Furthermore, it is found that, despite the significant differences in the models' dependencies, the resulting effects are quite similar. All models are found to have a narrowing influence on the pre-neutron emission mass- yield distributions, resulting in an increased peak-to-valley ratio. In the detection of fission fragments, a higher peak-to-valley resolution is often associated with a better mass resolution. This study shows that the plasma delay time could have a misleading influence in regards to estimating an experimental mass resolution.

The goal of this thesis is the development and application of model-independent analysis techniques to characterise New Physics states of different kinds from their signatures at the LHC and future colliders. In the first part of the thesis, we outline the general steps from the building of the simplified model and identification of the parameter space to the characterisation potential of the current searches with the focus on the characterisation between different scenarios of Beyond the Standard Model physics. We then demonstrate the outlined procedure on two specific and relevant examples: discrimination of exotic decays of vector-like quarks and determination of the spin of a dark matter candidate.

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