The detection of high-energy neutrinos in the E > O(PeV) range requires newdetection techniques in order to cope with the decreasing flux. The radio detectionmethod uses Askaryan emission to detect these neutrinos. The propagation of theradio pulses has to be modeled carefully in order to estimate the properties of theneutrinos from the detected radio pulse. This report introduces a model whichwas implemented to the NuRadioMC code to simulate birefringence effects in theice of the South Pole. To do that, a new ice model was created which combinesthe density and directional dependence on the refractive index. With this icemodel and an analytical ray tracer the time delay and polarization resulting frombirefringence was simulated for different geometries. A directional dependenceon the magnitude of the time delay and the change of the polarization along thepropagation path was found. To model the mixing of the polarization states dueto this change in polarization a pulse propagation model was introduced. Timedelay calculations resulting from this model were compared to simulations andmeasurements from the ARA experiment and have shown good agreement.

As the IceCube Neutrino Observatory seeks to expand its sensitivity to high PeV-EeV energies by means of the radio technique, the need for fast, efficient and reliable reconstruction methods to recover neutrino properties from radio detector data has emerged. The first recorded investigation into the possibilities of using a neural network based approach to flavor reconstruction is presented. More specifically, a deep convolutional neural network was built and optimized for the purpose of differentiating νe charged current (CC) interaction events from events of all other flavors and interaction modes. The approach is found to be largely successful for neutrino energies above 1018 eV, with a reported accuracy on νe - CC events of > 75% for neutrino energies > 1018.5 eV while maintaining a >60% accuracy for energies > 1018. Predictive accuracy on non- νe - CC events varies between 80% and 90% across the considered neutrino energy range 1017<Eν<1019. The dependence of the accuracy on νe - CC events on neutrino energy is pronounced and attributed to the LPM effect, which alters the features of the radio signals significantly at energies above 1018 eV in contrast to non- νe - CC events. The method shows promise as a first neural network based neutrino flavor reconstruction method, and results can likely be improved through further optimization.

The Department of Physics and Astronomy in Uppsala is planning to construct a source-based neutron irradiation facility at Ångströms laboratory. The purpose of this facility will, as of now, mainly be for students and employees to conduct scientific experiments and to calibrate the university's neutron scintillator detectors. A vital part of the construction is the shielding of the source, for both safety reasons and practicality issues. In this project, a series of simulations were made to determine the necessary dimensions of the shielding to ensure that the radiation dose levels stayed under the stipulated 6 mSv per year. Two types of shielding materials were tested, borated and non-borated polyethylene. It was found that the borated polyethylene performed better in shielding the source, but not enough to justify the higher material cost. The optimal dimensions of the shielding for non-borated polyethylene were found to be 60x60x74cm.

In this project, an algorithm has been implemented in Python to estimate the parameters describing the production and decay of a spin 1/2 baryon - antibaryon pair. This decay can give clues about a fundamental asymmetry between matter and antimatter. A model-independent formalism developed by the Uppsala hadron physics group and previously implemented in C++, has been shown to be a promising tool in the search for physics beyond the Standard Model (SM) of particle physics. The program developed in this work provides a more user-friendly alternative, and is intended to motivate further use of the formalism through a more maintainable, customizable and readable implementation. The hope is that this will expedite future research in the area of charge parity (CP)-violation and eventually lead to answers to questions such as why the universe consists of matter. A Monte-Carlo integrator is used for normalization and a Python library for function minimization. The program returns an estimation of the physics parameters including error estimation. Tests of statistical properties of the estimator, such as consistency and bias, have been performed. To speed up the implementation, the Just-In-Time compiler Numba has been employed which resulted in a speed increase of a factor 400 compared to plain Python code.

In this thesis, the feasibility to use a medium sized sodium cooled fast reactor fully loaded with MOX fuel for efficient transmutation of americium is investigated by simulating the safety performance of a BN600-type fast reactor loaded with different fractions of americium in the fuel, using the safety parameters obtained with the SERPENT Monte Carlo code. The focus is on americium mainly due to its long-term contribution to the radiotoxicity of spent nuclear fuel and its deterioration on core's safety parameters. Applying the SAS4A/SASSYS transient analysis code, it is demonstrated that the power rating needs to be reduced by 6% for each percent additional americium introduction into the reference MOX fuel, maintaining 100 K margin to fuel melting, which is the most limiting failure mechanism.Safety analysis of a new Accelerator Driven System design with a smaller pin pitch-to-diameter ratio comparing to the reference EFIT-400 design, aiming at improving neutron source efficiency, was also performed by simulating performance for unprotected loss of flow, unprotected transient overpower, and protected loss-of-heat-sink transients, using neutronic parameters obatined from MCNP calculations. Thanks to the introduction of the austenitic 15/15Ti stainless steel with enhanced creep rupture resistance and acceptable irradiation swelling rate, the suggested ADS design loaded with nitride fuel and cooled by lead-bismuth eutectic could survive the full set of transients, preserving a margin of 130 K to cladding rupture during the most limiting transient. The thesis concludes that efficient transmutation of americium in a medium sized sodium cooled fast reactor loaded with MOX fuel is possible but leads to a severe power penalty. Instead, preserving transmutation rates of minor actinides up to 42 kg/TWhth, the suggested ADS design with enhanced proton source efficiency appears like a better option for americium transmutation. / QC 20110318

The subject of extra dimensions has experienced a renewed interest in recent years. Arkani-Hamed, Dimopoulos, and Dvali (ADD) have pointed out that it is possiblethat there exist extra dimensions that are as large as micrometer sized, if theStandard Model fields are restricted to a four-dimensional brane. In the ADD model, only the graviton is able to probe the extra dimensions. The main motivation for this model is that it could solve the hierarchy problem between the electroweak scale and the Planck scale by lowering the Planck scale to 1 TeV. However, in the ADD model, the radius of the extra dimensions is large, giving a new hierarchy problem between this radius and the electroweak scale. In addition, there are significant constraints on the model coming from astrophysics. To improve on the ADD model, it is possible to consider a model with curved extra dimensions. An interesting scenario is provided by extra dimensions of hyperbolic geometry. In this case, it is possible to bring the Planck scale down to 1 TeV without the need of a large radius. Also, the constraints that are important for the ADD model can be completely avoided. The most efficient probe of large extra dimensions is particle physics. In particular, it is possible to study their phenomenology in high-energy particle accelerators such as the Large Hadron Collider, which will be completed in 2008. The phenomenology of the ADD model has been extensively studied. In this thesis, we consider the phenomenology of a model where the internal space is a hyperbolic disc. We obtain the Kaluza-Klein spectrum approximately and study the Kaluza-Klein modes. The results are cross sections for production of a graviton together with a photon or a hadronic jet, which are the most important reactions for LHC physics.

Unparticle physics is the physics of a hidden sector which is conformal in the infrared and coupled to the Standard Model. The concept of unparticle physics was introduced by Howard Georgi in 2007 and has since then received a lot of attention, including many studies of its phenomenology in different situations. After a review of the necessary background material, the implications of the self-interactions of the unparticle sector for LHC physics is studied. More specifically, analyses of four-body final states consisting of photons and leptons are performed. The results are upper bounds on the total cross sections as well as distributions of transverse momentum.

In this project, different fission models in the nuclear reaction code TALYS have been compared to GEF version 2020/1.2. The data included in the comparison are mass yield distributions, average prompt neutron energies per fragment mass, and average multiplicities of both neutrons and γ-rays per fragment mass. The reaction studied in the first part of the project is 1 keV neutron-induced fission of 235U. In the second part of the study, a variety of different nuclei and different incident energies were included in comparisons, but a limitation was set to only include neutron-induced fission. The results from the comparison suggested that TALYS fymodel 2 and 3 were less consistent with GEF than fymodel 4. For the comparisons with experimental data, fymodel 4 also performed better overall. TALYS fymodel 2 and 3 make use of implemented partial versions of GEF to produce fission fragment distributions, while fymodel 4 takes fission fragment distribution data from separate yieldfiles. A database of these yieldfiles with 737 different nuclei and 10 energy levels was produced, to be implemented in future versions of TALYS. The energy levels were chosen to get a range of energies that can be accurately interpolated between. This method of using TALYS fymodel 4 with a yieldfile from GEF consistently showed a strong agreement with GEF version 2020/1.2 for the mass yield distributions and the neutron multiplicities. The γ-ray multiplicities and the neutron energies show a slightly weaker agreement, and TALYS gives consistently smaller values than GEF for these quantities.

The presented project explores the current theoretical and experimental tools available within the study group for the Future Circular Collider (FCC) with focus on the electron-positron collider. The aim of the study is to evaluate the current frameworks used for simulation, and investigate the possibility of simulating long-lived particles, that could be dark matter candidates, through them. Pythia cards were run through the framework of Delphes and several different software packages were studied on the journey through the work. It was found that the current framework reconstructs the masses of a Z bosons and Higgs bosons accurately from the ZH signal, which is central for the analysis at the FCC-ee. When the same analysis was applied for the new physics case of a dark matter particle included in the new card for study, a ROOT file was produced indicating that the framework was able to handle the new case. When this card was run through the analysis software however, difficulties arose and a final output could not be achieved. Conclusively, it can be said that the current framework has the possibilities of handling new physics cases but further study is required to be able to run certain software packages on these cases.

Even though there is a multitude of observational evidence from cosmology and astrophysics, the standard model does not include a suitable dark matter candidate and therefore physics beyond the standard model is necessary. There are hypotheses of what the particle candidate could be coming from theories such as supersymmetry or extra dimensions. The processes producing these particles are understood very well from the theoretical perspective. The problem is that these processes have not been observed in any detectors. Therefore the nature of the dark matter remains unknown. However, it is clear that the dark matter-particle interacts with ordinary matter through gravity and in general, candidates may also interact through the weak force. These candidates are called Weakly Interacting Massive Particles. Therefore, by studying weak processes (weak in the sense that the processes are interactions mediated by a force weaker than the Electro-Magnetic and Quantum-Chromo dynamical-forces, not necessarily the weak force of the standard model) in the large hadron collider it may be possible to pose constraints on the dark matter signatures. One possible process which specifically involves the standard model electroweak interaction, which will be the model for the project, is the emission of scalar dark matter particles from the Z boson,which would result in a final state characterized by a Z boson and missing transverse energy. Simulations of the model and calculations of the cross section are done for different masses, ranging from 20−680 GeV, of the scalar dark matter particle and then compared to a standard model background process. Investigations are made whether or not it would be possible to detect darkmatter signals in the background. With the assumptions made, the results indicate that a signal from dark matter with a mass of around 40−150 GeV could not be rejected up to 5σ.