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1
Ingebretsen, Carlson Tom. "Characterization of the Spin of Dark Matter at the LHC." Thesis, Uppsala universitet, Högenergifysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-388421.
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The potential for characterizing the spin and mass of dark matter at the Large Hadron Collider (LHC) given a 5 sigma confidence level discovery has been studied. The search for dark matter is one of the big open question in particle physics as observations predict 84 percent of the matter in the universe to be dark matter, however no detection has been made. In this study two production channels at the LHC of weakly interacting massive particles with different spin have been studied in the framework of a simplified model. The processes if detected have the signature of a mono-jet and missing transverse energy. The assumption made is that the dark matter is a scalar or a Dirac fermion particle and interacts with the top quark and a Beyond the Standard Model color charged mediator via a loop process. The considered mediators are a scalar top partner and a fermionic top partner. The results from recasting conclude that in a narrow region in the mass-mass-plane for the dark matter and the mediator a search is adequate and given a discovery characterization of the spin and mass is possible.
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Sjöberg, Josefine. "Coincidences between neutrons and gammas." Thesis, Uppsala universitet, Tillämpad kärnfysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-389686.
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The neutron is a valuable tool in many fields of science due to its properties regarding electric charge and magnetic moment. However, these properties also makes it difficult to detect. Through simulation one can optimize the detector environment to best correspond with the needs for a specific experiment. In this project, a detector environment is simulated, consisting of a neutron and gamma point source and one detector for each type of particle. The simulated results were in good agreement with the underlying theory and the simulation can, therefore, be used in future work.
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Jansson, Peter. "Studies of Nuclear fuel by means of Nuclear Spectroscopy Methods." Licentiate thesis, Uppsala universitet, Institutionen för kärn- och partikelfysik, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-85900.
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This paper which is a thesis for the title teknologie licentiat is a summary text of several works performed by the author regarding spectroscopic measurements on spent nuclear fuel. Methods for determining the decay heat of spent nuclear fuel by means of gammaray spectroscopy and for verifying the integrity of nuclear fuel by means of tomography is presented. A summary of work performed regarding gammaray detector technology for studies of fission gas release is presented.
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Wollter, August. "Sensitivity Study of Higgs Boson Pair Production with WWττ Final States at 13 TeV in the ATLAS Experiment." Thesis, Uppsala universitet, Högenergifysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-372508.
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This feasibility study concerns the implementation and analysis of a Higgs pair decaying to two W bosons, with hadronic final states, and to two τ-leptons, one with a leptonic and one with a hadronic final state, hh→ WhadWhad τlepτhad, in the ATLAS detector at the CERN Large Hadron Collider, by adapting the ``CxAOD framework'' software analysis code of the hh→ bbττ analysis. The purpose is to compare the sensitivity of this final state with other di-Higgs analyses in the ATLAS collaboration. Monte Carlo samples are used for the background and signal simulation. A cut based selection is then performed based on several kinematic variables. Finally, a statistical analysis is performed on the MMC mass distribution of the ττ system. The cross section can be limited at the 95 % confidence level to σexpected < 89.8 fb, compared to the theoretical σSM = 0.19 fb.
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Mathisen, Thomas. "Studies of Hypothetical Vector-Like Quarks at the Large Hadron Collider." Thesis, Uppsala universitet, Högenergifysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-353432.
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A study for the search for vector-like quarks and a new pseudo Nambu-Goldstone boson(pNGB) scalar at the LHC running at $\sqrt{s} = 13$ TeV is presented. A model based on the composite Higgs model in which the Higgs boson emerges as a composite pNGB together with a new pNGB $\eta$ is considered. Simulations are made on the modelshowing a low ratio between signal to background indicating no significance and a low discovery potential. However, further studies are needed as more channels should be investigated. Moreover, a more sophisticated analysis is needed to properly reject the background and for a more thorough statistical analysis. Even so, results still show potential in the search as there do exist distinct differences between signal and SM background.
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Gong, Enze. "Scattering Amplitudes of F3-deformed Gauge Theories in the CHY-formalism." Thesis, Uppsala universitet, Teoretisk astrofysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-449308.
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Waagaard, Elias. "Identied Multiplicity Dependence Of Primary Strange Particle Production." Thesis, Uppsala universitet, Kärnfysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-395046.
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Dimitriadi, Christina. "Unfolding of multivariate tools and statistical analysis for Higgs boson pair production searches in the ATLAS detector at the Large Hadron Collider." Thesis, Uppsala universitet, Högenergifysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-394393.
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Recently, searches for pair production of Higgs bosons in several final states have been carried out by the ATLAS exeperiment at the Large Hadron Collider (LHC). This study focuses on the search for non-resonant di-Higgs production decaying to a final state with two b-jets and two τ-leptons using 36.1 fb-1 of data recorded by the ATLAS detector. The analysis for this process has already been performed. Boosted decision trees (BDTs) are used in the analysis to improve the separation of the signal from background processes and several variables that provide good discrimination between signal and background are used as inputs to the BDT. This study aims to unfold the BDT of the analysis and optimize a cut-based analysis so that the gain from using the BDT can be estimated. Two variables, related to the invariant masses and angular distances of the Higgs boson decay products, are defined and the optimal cuts are found to be Xmττmbb<1.8 and XΔRττΔRbb <4.0. Then, the upper limits on the SM HH production cross section are set when fitting mHH with the cut-based analysis. An expected limit of 0.78 pb, 23 times the SM prediction is obtained when neglecting systematic uncertainties, compared to the limit of 15 times the SM as recomputed when using the BDT. Comparing the two results, the sensitivity is worsened by 50% when not using the BDT.
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Shaikh, Nabila. "Energy Calibration of the Tile L1Calo and Data Driven Estimation of Non-prompt $e$, $\mu$ and $\tau$ Background Using Data From the ATLAS Detector." Licentiate thesis, Stockholms universitet, Fysikum, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-156377.
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Gabro, Dany. "Estimating fission fragmentangular momentum using TALYS." Thesis, Uppsala universitet, Tillämpad kärnfysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-411470.
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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.
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Rygaard, Lovisa, and Andreas Ström. "Simulations of fission fragments in VERDI : A study of the Plasma Delay Time phenomenon." Thesis, Uppsala universitet, Tillämpad kärnfysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-412949.
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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.
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Timmy, Lindgren. "Reconstruction of challenging signatures characteristic to new physics beyond the Standard Model with the ATLAS detector." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-414984.
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Salko, Jakub. "Characterisation of Models of New Physics at the LHC." Thesis, Uppsala universitet, Högenergifysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-421416.
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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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Pereira, Sanchez Laura. "b-jet identification and searches for supersymmetry, dark matter and Higgs boson pair production with the ATLAS experiment." Licentiate thesis, Stockholms universitet, Fysikum, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-186308.
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Andersson, Martin. "Investigating the Electron Reconstruction Efficiency at the LHCb." Thesis, Uppsala universitet, Högenergifysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-433778.
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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%.
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Lundqvist, Tobias. "Investigation of Algebraic Reconstruction Techniques for Tomographic Measurements on Spent Nuclear Fuel Assemblies." Thesis, Uppsala universitet, Institutionen för strålningsvetenskap, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-307832.
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A non-destructive tomographic measurement technique for application on nuclear fuel assemblies has beendeveloped at the Uppsala University. Using this technique, the rod-by-rod distribution of selectedradioactive isotopes is determined experimentally. In the present work, the numerical technique to reconstruct the activity distribution inside the fuelassemblies has been analyzed. Three iterative reconstruction algorithms have been investigated, ART(Additive Reconstruction Technique), ML (Maximum Likelihood) and ASIRT (Additive SimultaneousIterative Reconstruction Technique). It was found that the ART algorithm is too sensitive to data points where the gamma-ray intensityis low, while ASIRT handles it in the best manner. Furthermore, ASIRT appears to be the most stablealgorithm and produces the best agreement to theoretical data.
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Gazit, Yonatan. "Quantum Speed Limits of Spin Chain Dynamics : Applying Quantum Speed Limits to Spin Chains used as Quantum Channels." Thesis, Uppsala universitet, Teoretisk fysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-323292.
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Quantum computers, like classical ones, need to be capable of sending informa-tion between different parts of the computer. Spin chains are one viable method of sending qubits while preserving the superposition and entanglement of a state. We use quantum speed limits, which give bounds on how fast non-relativistic quantum systems can evolve, to study simple Heisenberg chains and their efficacy as quantum channels.
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Hallberg, Ludvig. "Analysis of triple gamma coincidences for studies of the level structure of nuclei in the 100-Sn region." Thesis, Uppsala universitet, Kärnfysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-325862.
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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%.
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Elevant, Jessica. "Phenomenological Studies of Neutrinos." Licentiate thesis, Stockholms universitet, Fysikum, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-143296.
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Mattera, Andrea. "Studying neutron-induced fission at IGISOL-4 : From neutron source to yield measurements and model comparisons." Doctoral thesis, Uppsala universitet, Tillämpad kärnfysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-328484.
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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.
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Changizi, Sara A. "Pairing correlation in atomic nuclei under extreme conditions." Doctoral thesis, KTH, Skolan för teknikvetenskap (SCI), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-217522.
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The pairing correlation has long been recognized as the dominant many-body correlation beyond the nuclear mean field. Pairing plays an essential role in many nuclear phenomena including the occurrence of a systematic odd-even staggering (OES) of the nuclear binding energy. Pairing interaction plays, in particular, a significant role in the stability of weakly bound nuclei. Therefore it has been one of the most critical topics in nuclear physics because of the weakly bound structure of all newly discovered nuclei. Beyond the line of stability, pairing interaction is not a residual interaction anymore. Its strength can be of the same order of magnitude as the mean field. In this thesis we have focused on the pairing interaction in atomic nuclei under extreme conditions to investigate the structure of loosely bound nuclei near the dripline; to probe and globally assess different outcomes of various zero-range pairing interactions and their effect on the loosely bound low angular momentum states. How much can density-dependence in zero-range pairing interaction nuclei affect the line of stability? Calculations predict that pure density-dependent pairing interaction so-called surface interaction enhances the collectivity and gives stronger neutron pairing gap in nuclei far from stability, while, the density dependence pairing interaction does not affect the gap for bound nuclei as much. The odd-even staggering of nuclear binding energies has been investigated to estimate the empirical pairing gap. A 3-point formula Δ(3)C (1/2[B(N,Z)+B(N −2,Z)−2B(N −1,Z)]) is advocated in this thesis, which we believe it is more suitable to measure the magnitude of pairing gap in even-even nuclei. The strength of Δ(3)C can be a good indicator of the two-particle spatial correlation. One-quasiparticle energies and binding energy for those odd nuclei, which can be approximated by spherical symmetry, are calculated to obtain binding energy odd-even staggering (OES) in all known semi-magic even-even nuclei. The pairing strength is fitted globally to all available data on the OES of semi-magic nuclei with Z ≥ 8. The difference between different zero-range density-dependent pairing interactions reduces with this global fitted parameter. The difference between the mean pairing gap and the OES gets larger as we get closer to the dripline. At the end of the thesis, a simple model has been developed which shows that when the mean-field becomes shallower the odd-even staggering of charge radii is reduced.This thesis covers results that are not included in the three published papers and some complementary works on the subject.Parkopplingen i atomkärnan anses vara den dominerande mångkropparskorrelationen efter kärnmedelfältet. Parkoppling i atomkärnan spelar en viktig roll i många kärnfenomen,inklusive förekomsten av en systematisk udda-jämn förskjutning (OES) av bindningsenergin.Hos svagt bundna atomkärnor däremot spelar parkopplingen en signifikant roll för stabiliteten. Det gäller alla de nyupptäckta neutronrika atomkärnor som karakteriseras aven svag bindningsenergi där således parkopplingen blir ett kritiskt fenomen. När vi lämnar stabilitetslinjen och närmar oss linjen av spontan neutronsönderfall är parkopplingeninte längre obetydlig, utan tvärtom spelar en viktig roll för stabiliteten hos atomkärnan.Dess styrka kan vara av samma storleksordning som medelfältet. I denna avhandling har vi fokuserat på parkopplingen i atomkärnor under extrema villkor i syfte att undersöka strukturen hos löst bundna atomkärnor nära linjen för neutronsönderfall; att utforska och globalt bedöma resultaten av olika parkopplingar baserad på en deltakraft (räckvidd noll) och deras effekt på löst bundna tillstånd med lågt rörelsemängdsmoment. Hur mycket kan ett täthetsberoende i parkopplingen påverka stabilitetslinjen? Beräkningarna förutsäger att ren densitetsberoende växelverkan för parkoppling, så kallad ytväxelverkan, ökar kollektiviteten i atomkärnan och ger ett större pargap för neutroner i kärnor långt ifrån stabilitetslinjen,medan densitetsberoende parkoppling påverkar inte gapet för bundna kärnor i samma omfattning.Udda-jämn-spridning av bindningsenergier har undersökts för att hitta storleken på parkopplingens gap. En 3-punktsformel Δ(3)C (1/2[B(N,Z)+B(N −2,Z)−2B(N −1,Z)]) förespråkas i denna avhandling, som vi anser vara mera lämplig för att mäta storleken på pargapet i jämn-jämna kärnor. Storleken på Δ(3)C kan vara en bra indikator på rumskorrelationen mellan två nukleoner. En-kvasipartikelenergi för de udda kärnorna, som kan approximeras med sfärisk symmetri, beräknas för att erhålla udda-jämn spridning (OES) med avseende på bindningsenergin för alla kända semi-magiska jämn-jämna kärnor. Parkopplingsstyrkan är globalt anpassat med all tillgänglig data på OES vad gäller semi-magiska kärnor med Z ≥ 8. Skillnaden mellan olika täthetsberoende parkopplingar med vår växelverkan minskar med dessa globalt anpassade parametrar. Skillnaden mellan det teoretiska genomsnittliga parkopplingsgapet och OES blir större när vi kommer närmare tröskeln för atomkärnans stabilitet. I slutet av avhandlingen har en schematisk modell utvecklats som, genom attgöra medelfältet grundare, reducerar de udda-jämnt spridda laddningsradierna. Avhandlingen innehåller dessutom resultat som inte ingår i de tre publicerade artiklarna samt några kompletterande arbeten om ämnet.
QC 20171114
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Nair, Shankar. "CP Violation in Σ0 decay." Thesis, Uppsala universitet, Kärnfysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-338618.
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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
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Reza, Zadeh Hamid Reza. "Sterile Neutrinos and Cosmology." Thesis, Uppsala universitet, Högenergifysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-338759.
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Wollter, August. "MSSM Higgs to τ τ and Optimizing Sensitivity : Report for Advanced Physics - Project Course 1FA565." Thesis, Uppsala universitet, Högenergifysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-346776.
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I replicated the H/A → τ μ τ had analysis of the MSSM extension to the stan-dard model with the ATLAS experiment. I investigated, using a transformedBDT score for τ -lepton identification with a flat distribution, with more work-ing points than the standard loose, medium and tight, the sensitivity of theanalysis. I then compared for each of the working points and found new signalefficiencies that are more sensitive for this analysis than the standard workingpoints.I replicated the H/A → τ μ τ had analysis of the MSSM extension to the stan-dard model with the ATLAS experiment. I investigated, using a transformedBDT score for τ -lepton identification with a flat distribution, with more work-ing points than the standard loose, medium and tight, the sensitivity of theanalysis. I then compared for each of the working points and found new signalefficiencies that are more sensitive for this analysis than the standard workingpoints.
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Aler, Tubella Andrea. "A study of normalisation through subatomic logic." Thesis, University of Bath, 2017. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.715305.
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We introduce subatomic logic, a new methodology where by looking inside of atoms we are able to represent a wide variety of proof systems in such a way that every rule is an instance of a single, regular, linear rule scheme. We show the generality of the subatomic approach by presenting how it can be applied to several different systems with very different expressivity. In this thesis we use subatomic logic to study two normalisation procedures: cut-elimination and decomposition. In particular, we study cut-elimination by characterising a whole class of substructural logics and giving a generalised cut-elimination procedure for them, and we study decomposition by providing generalised rewriting rules for derivations that we can then apply to decompose derivations and to eliminate cycles.
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Göök, Alf. "Investigation of the Frisch-grid inefficiency by means of wave-form digitization." Thesis, Örebro University, Institutionen för naturvetenskap Department of Natural Sciences, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-4791.
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Frisch grid ionization chambers are commonly used experimental tools for charged particle spectroscopy. In the ideal Frisch grid chamber the anode pulse height is independent of where inside the sensitive volume the charge has been created. This ideal cannot be realized because of imperfect shielding of the anode by the grid. The effect of the imperfect shielding is generally referred to as grid inefficiency. For accurate energy determination the anode pulse height needs to be corrected for this.
At present two opposing explanation for grid inefficiency exist. The first explanation suggests that there is a reduction of the anode pulse height. This is said to arise from positive ions inducing charge on the anode as the electrons are collected. The second explanation suggests that there is a too large anode signal. The addition to the anode signal is said to arise from the drift of electrons.
In this thesis the concept of grid inefficiency is investigated by means of wave form digitization. The use of digital signal processing makes it possible to maintain information on the drift of electrons. This information is lost in charged particle spectroscopy experiments using electronic signal processing networks.
A series of experiments is described in this thesis. The first experiment was performed to find good measuring conditions for the following experiments. For this purpose the drift velocity of electrons was measured in two chamber filling gases, P-10 and CF4. The measured drift velocities are presented for the two gases. Finally, P-10 was chosen as filling gas for the following experiments.
In the second experiment the grid inefficiency was measured for two different types of shielding electrodes. The method of determining the grid inefficiency is based on the analysis of the shape of digitized charge signals. The measured values are shown to be in good agreement with calculated values.
In the final experiment the effects of grid inefficiency on alpha particle spectroscopy is investigated. It is shown how the correction for grid inefficiency by the two existing models yield equivalent results for energy determination. An attempt to separate the two models is also presented indicating that there is in fact a reduction of the anode pulse height because of grid inefficiency. The thesis is concluded with a theoretical discussion of the anode pulse shape. There grid inefficiency is explained by the drift of electrons. It is shown in this section how explaining grid inefficiency by the drift of electrons should yield the same result as explaining it by the effect of positive ions.
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Pérez, Andrade Gabriela. "Production of the Σ0-bar hyperon in the PANDA experiment at FAIR." Thesis, Uppsala universitet, Kärnfysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-375552.
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The PANDA experiment is one of the main pillars of the Facility for Antiproton and Ion Research (FAIR), currently under construction in Darmstadt, Germany. PANDA will be a fixed target experiment designed for the study of non-perturbative phenomena of the strong interaction. Strange hyperon production is governed by m(s) ~ 100 MeV, which corresponds to the confinement domain. Thus, hyperons are suitable probes in this energy region. This work is a simulation study focused on the feasibility of studying the production of Σ0-bar and Λ hyperons in the pbar p -> Σ0-bar Λ reaction with the PANDA detector. A 10^4 events sample simulated at p(beam) = 1.771 GeV/c is used to perform a single-tag (inclusive) and a double-tag (exclusive) event selection. From the former, it is concluded that the single-tag method does not provide with the clean signal required for spin observables extraction. In contrast, exclusive event selection provides with a signal reasonably clean from combinatorial background and completely clean from generic hadronic background events. A signal (Σ0-bar Λ) reconstruction efficiency of ε = 5.3 ± 0.2 % is obtained for exclusive event selection. The corresponding signal to background ratio is S/B(Total) ~ 6 and the significance value is ~ 21. In addition, an exclusive event selection is performed on a 10^4 events sample simulated at p_(beam) = 6 GeV/c. Almost all the generic hadronic background events are removed by the applied selection criteria. At this beam momentum, the obtained signal efficiency is ε = 6.1 ± 0.3%, the signal to total background ratio is S/B(Total) ~ 4 and the significance is ~22. Both efficiencies are smaller compared to a previous simulation study on this channel, but are large enough to enable a study of the exclusive production of the pbar p -> Σ0-bar Λ reaction at PANDA. The difference between the results of this thesis work and the previous work is attributed to the more realistic implementation of the signal production mechanism, as well as the detector and reconstruction algorithms.
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Ripellino, Giulia. "A search for Supersymmetry in final states with two same-flavor opposite-sign leptons, jets and missing transverse momentum with the ATLAS detector." Licentiate thesis, KTH, Partikel- och astropartikelfysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-220892.
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This thesis presents a search for Supersymmetry in final states containing two same-flavor opposite-sign leptons, jets and large missing transverse momentum. The search makes use of 36.1 fb−1 of proton-proton collision data collected at a center-of-mass energy of √s = 13 TeV by the ATLAS detector at the Large Hadron Collider. Two signal scenarios, which both involve the pair-production of squarks or gluinos decaying into final states with two leptons and the lightest supersymmetric particle, are targeted by the analysis. The first scenario considers decay chains with a leptonically decaying Z boson and is characterized by a peak in the dilepton invariant mass distribution. In the second scenario, decays through intermediate sleptons or an off-shell Z boson are considered. Such processes lead to a kinematic endpoint in the dilepton invariant mass distribution. The main Standard Model backgrounds include the pair-production of top quarks and direct production of Z bosons. These backgrounds are estimated with two data-driven methods. The observed data is found to be consistent with the Standard Model expectation and the results are interpreted in simplified Supersymmetry models for gluino and squark pair-production. Sensitivity is provided for gluino and squark masses up to 1.85 TeV and 1.3 TeV respectively.I denna avhandling presenteras en analys som letar efter supersymmetriska partiklar producerade i proton-proton-kollisioner vid en kollisionsenergi på √s = 13 TeV. Analysen använder sig av data insamlad under 2015 och 2016 av ATLAS-experimentet vid CERNs Large Hadron Collider. Den totala analyserade datamängden motsvarar 36,1 fb−1. Kollisioner som resulterar i par av elektroner eller myoner med motsatt laddning, jets och en stor obalans i rörelsemängd i det transversella planet väljs ut för analys. Målet är att finna tecken på en produktion av skvarkar eller gluiner som sönderfaller till två leptoner och en oladdad supersymmetrisk partikel som lämnar detektorn utan att lämna någon signal. Inom supersymmetriska modeller kan sådana slutliga tillstånd uppkomma genom sönderfallskedjor med Z-bosoner som sönderfaller leptoniskt, eller genom sönderfallskedjor med sleptoner. Flera processer som förutspås av Standardmodellen kan efterlikna den eftersökta signalen och utgör bakgrunder i analysen. De viktigaste bakgrunderna består av Z-bosoner och par av toppkvarkar som produceras direkt i proton-proton-kollisionerna. Dessa bakgrunder uppskattas genom att använda data, medan andra mindre bakgrunder uppskattas genom att använda simuleringar. Ingen signifikant signal utöver den uppskattade backgrunden uppmäts i analysen. Istället tolkas resultaten med hjälp av simuleringar av förenklade supersymmetriska modeller. På så sätt kan exkluderingsgränser med 95% konfidensnivå beräknas för gluino- och skvark-massorna. Massor över 1,85 TeV utesluts för gluiner och massor över 1,3 TeV utesluts för skvarkar.
QC 20180109
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Lyubimov, Artem L. "A structural study of cholesterol oxidase at atomic and subatomic resolution /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2006. http://uclibs.org/PID/11984.
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Cardoso, Mário. "Study of pattern recognition of particle tracks with neural networks." Thesis, Uppsala universitet, Högenergifysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-454374.
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In this project we study the use of neural networks as a tool for particle track pattern recognition with the possibility of its implementation in the Trigger system at the ATLAS experiment [1]. By using a method named Hough transform we created a Convolutional Neural Network (CNN) that is able to train on the transformed images of muons merged with minimum bias. We give an overview of how the CNN works and compare the results from the CNN with the old cut based method. We believe to have managed to find an alternative to the previously used algorithm, that is faster and more efficient.
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Lindgren, Timmy. "Reconstruction of challenging signatures characteristic to new physics beyond the Standard Model." Thesis, Uppsala universitet, Högenergifysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-420286.
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A study of photon-jets and their identification variables computed in the electromagnetic calorimeter of an in-house, ATLAS-like, detector model developed at Uppsala University for full-simulations is presented. The signal, which is based on the Composite Higgs Model, considers the pair production of vector-like top quarks, denoted t', with the successive decays t' to S and a Standard Model top quark and S to two photons, where S is a new pseudo-scalar boson. For clustering purposes, Topological Clustering was implemented and compared against the already implemented Sliding Window clustering algorithm. A modification to the Topological Clustering algorithm used in the ATLAS detector was made and compared against the original version. The performance test showed a significant mass reconstruction improvement with Topological Clustering. Furthermore, the performance test showed some improvement with the modifications in the Topological Clustering for photons in a collimated scenario. The signal is compared to Standard Model background consisting of one photon plus zero, one or two jets, and isolated photons from the Higgs boson decaying into two photons. Even though some discrimination could be found, the analysis showed that standard cut and count strategy won't work and hence, further analysis with machine learning should be tested.
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Rol, Jan. "Characterization of monopole induced air showers using CORSIKA." Thesis, Uppsala universitet, Högenergifysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-328049.
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In this thesis a characterization of air showers induced by magnetic monopoles is presented. Monopoles are predicted to exist and be accelerated to relativistic velocities. High energy monopoles traversing earth’s atmosphere continuously deposit energy, inducing an air shower. These air showers have been described based on simulations run in CORSIKA. It was found that monopole air showers are continuous; they plateau after the shower maximum, and have a large electromagnetic component. As such,they can easily be distinguished from normal cosmic rays and most other air shower sources. Very high energy photons and muons could induce similar showers but do not produce identical signals in track-following detectors such as IceCube.
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Ohlsson, Sophie. "Test and Developments of Crystals for a High-Resolution Electromagnetic Calorimeter for PANDA." Thesis, Uppsala universitet, Fysiska sektionen, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-142869.
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Grape, Sophie. "PWO Crystal Measurements and Simulation Studies of Anti-Hyperon Polarisation for PANDA." Licentiate thesis, Uppsala universitet, Kärnfysik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-142861.
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The Gesellschaft für Schwerionenforschung (GSI) facility in Darmstadt, Germany, will be upgraded to accommodate a new generation of physics experiments. The future accelerator facility will be called FAIR and one of the experimentsat the site will be PANDA, which aims at performing hadron physics investigations by colliding anti-protons with protons. The licentiate thesis consistsof three sections related to PANDA. The first contains energy resolutionstudies of PbWO4 crystals, the second light yield uniformity studies of PbWO4 crystals and the third reconstruction of the lambda-bar-polarisation in the PANDA experiment. Two measurements of the energy resolution were performed at MAX-Lab in Lund, Sweden, with an array of 3x3 PbWO4 crystals using a tagged photon beam with energies between 19 and 56 MeV. For the April measurement, the crystals were cooled down to -15 degrees C and for the September measurement down to -25 degrees C. The measured relative energy resolution,
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Brännström, Hanna. "Di-Higgs Production in the Standard Model and Beyond." Thesis, Stockholms universitet, Fysikum, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-194419.
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This thesis examines how the kinetic properties of pair-produced Higgs bosons depend on whether the process is mediated by particles in the Standard Model or a simplified supersymmetric model. The analysis is based on simulated data made using MadGraph. The examination within this thesis is split into two parts, one performed on the output of MadGraph (parton level) and the second performed on the output of a simplified simulation of the ATLAS detector response (reconstruction level). The first part also contains a section showing that the supersymmetric model results are consistent with the Standard Model results in cases where no supersymmetric particles are present in the di-Higgs production and decay, and a section detailing the minor differences in kinematics of the Higgs bosons depending on the mass of the supersymmetric partner of the top quark. The second part of the thesis covers the decay of the Higgs boson into bottom and anti-bottom quarks, and includes a section showing that there is no difference if the decay is done using the MadSpin module or the Pythia module for MadGraph, before exploring the kinematics of the jets produced. Both when studying Higgs bosons at the parton level and when studying b-jets at the reconstruction level, it is found that there are clear differences in the kinematics between the Standard Model and the supersymmetric model. At both levels, a neural network has been designed, trained and tested. For the parton level neural network 59 % of all events are classified correctly, while at the reconstruction level 51 % of all events are classified correctly. These neural network results show that it is possible to train a neural network to learn on data like this, and that with enough di-Higgs events detected, their kinematic properties could be used to indirectly infer the presence of physics beyond the Standard Model.
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Winding, Jacob. "Localization, supersymmetric gauge theories and toric geometry." Doctoral thesis, Uppsala universitet, Teoretisk fysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-318668.
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Gauge theories is one of the most pervasive and important subject of modern theoretical physics, and there are still many things about them we do not understand. In particular dealing with strongly coupled theories where normal perturbative techniques do not apply is a fundamental open problem. In this thesis, we study a particular class of toy-models that have supersymmetry, which makes them much easier to deal with. We employ the mathematical technique of localization, which for supersymmetric theories lets us evaluate certain path integrals exactly and for any value of the coupling. This is used to study the 5d N=1 theories placed on toric Sasaki-Einstein manifolds and compute their partition functions, finding that they factorize into a product of contributions from each closed Reeb orbit of the manifold. This computation leads us to define two new hierarchies of special functions associated to these manifolds, and we study their properties. Finally, we use the 5d N=1 theories to construct new 4d N=2 theories on a large class of curved backgrounds. These theories have some interesting features, such as supporting both instantons and anti-instantons, and having a position-dependent complexified coupling constant.
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Bertilsson, Magnus. "Looking for mono-Z signatures in Z-boson and scalar dark matter interactions." Thesis, Uppsala universitet, Högenergifysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-449090.
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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.
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Thorén, Viktor. "Study of Discrete Symmetries in η' Meson Decays with BESIII." Thesis, Uppsala universitet, Kärnfysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-329747.
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This thesis studies the rare decay η' → π+π-e+e- using Monte Carlo simulations and data from the BES-III detector in Beijing, China. The branching ratio of the reaction was measured at BES-III in 2013 using a data set of 225×106 J/Ψ events. This work lays the groundwork for an updated branching ratio measurement using the full data set of 1.3×109 J/Ψ and determines a potential CP-violating asymmetry in the angle between the decay planes of the π+π-- and e+e--pairs. A total of 2558 signal events are observed after cuts, and the asymmetry parameter is determined to be Aφ = (1.96 ± 1.97stat.± 0.4syst. ) × 10-2. The result is consistent with zero within the uncertainty.
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Gradin, Joakim. "Searching for a charged Higgs boson and development of a hardware track trigger with the ATLAS experiment." Doctoral thesis, Uppsala universitet, Högenergifysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-329227.
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This thesis describes searches for a heavy charged Higgs boson decaying into a top and bottom quark pair, and the development of a hardware track trigger with theATLAS experiment. The data for the two searches was collected with the ATLAS detector at the Large Hadron Collider(LHC) with pp collision energies of √s = 8 and 13 TeV, and corresponds to an integrated luminosity of 20.3 and 13.2 fb-1 respectively. The main background for this signal is the production of tt̄ pairs with additional heavy flavor radiation. The searches with a single lepton in the final state found no evidence of a charged Higgs boson, and set 95% CLS upper limits on the production times branching ratio for masses ranging between 200-1000 GeV. The preparation of using the final state with two leptons in future searches is discussed. The design of a hardware track trigger based on pattern matching and linear track fitting was studied for the purpose of reducing the high event rates of the High-Luminosity LHC, which is expected to provide pp collisions with a luminosity about five times the nominal value, in the second half of the 2020’s. A simulation framework was developed to emulate the pattern matching and was used to test its ability to filter hits in high pile-up environments. The results of this simulation, together with simulations of the track fitting and latency, show that such a track trigger is a viable option for the ATLAS experiment in the High Luminosity-LHC era.
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Jansson, Kaj. "Measurements of Neutron-induced Nuclear Reactions for More Precise Standard Cross Sections and Correlated Fission Properties." Doctoral thesis, Uppsala universitet, Tillämpad kärnfysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-329953.
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It is difficult to underestimate the importance of neutron cross section standards in the nuclear data field. Accurate and precise standards are prerequisites for measuring neutron cross sections. Two different projects are presented here with the aim of improving on neutron standards. A simulation study was performed for an experiment intended to measure the cross sections of H(n,n), 235U(n,f), and 238U(n,f) relative to each other. It gave the first estimates of the performance of the experimental setup. Its results have aided the development of the experimental setup by setting limits on the target and detector design. A second neutron-standard project resulted in three measurements of 6Li(n,α)t relative to 235U(n,f). Each subsequent measurement improved upon the previous one and changed the experimental setup accordingly. Although, preliminary cross sections were agreeing well with evaluated data files in some energy intervals, the main goal to measure the cross section up to 3 MeV was not reached. Mass yields and energy spectra are important outcomes of many fission experiments, but in low yield regions the uncertainties are still high even for recurrently studied nuclei. In order to understand the fission dynamics, one also needs correlated fission data. One particular important property is the distribution of excitation energy between the two nascent fission fragments. It is closely connected to the prompt emission of neutrons and γ’s and reveals information about how nucleons and energy are transferred within the fissioning nucleus. By measuring both the pre and post neutron-emission fragment masses, the cumbrance of detecting neutrons directly is overcome. This is done using the fission spectrometer VERDI and the 2E-2v method. In this work I describe how both the spectrometer, the analysis method, and the calibration procedures have been further developed. Preliminary experimental data show the great potential of VERDI, but also areas that call for more attention. A previously overlooked consequence of a central assumption was found and a correction method is proposed that can correct previously obtained data as well. The last part of this thesis concerns the efficiencies of the fission product extraction at the IGISOL facility. The methodology of the fission yield measurements at IGISOL are reliant on assumptions that have not been systematically investigated. The presented work is a first step of such an investigation that can also be used as a tool for optimising the setup for measurements of exotic nuclei. A simulation framework connecting three different simulation codes was developed to investigate the produced yield of fission products in a buffer gas. Several different variants of the setup were simulated and the findings were generally accordant with previous estimates. A reasonable agreement between experimental data and the simulation results is demonstrated.
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Vaheid, Halimeh. "Monte Carlo Simulation of e + e − → Σ̄ 0 Λ/ Σ̄ 0 Σ 0 Reaction." Thesis, Uppsala universitet, Kärnfysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-339808.
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A central objective of the field of nuclear physics is understanding the fundamental properties of hadrons and nuclei in terms of QCD. In the last decade, a large range of experimental and theoretical methods have been developed to study the nature of quark confinement and the structure of hadrons which are composites of quarks and gluons. One important way to address some questions of hadron physics is studying the electromagnetic form factors of hadrons. The electric and magnetic form factors are related to the distribution of charge and magnetization in hadrons.The internal structure of hyperons, which are a subgroup of hadrons, is a topic of interest of particle physicists. The BES III experiment is one of the few current facilities for studying hadron structure.The Uppsala Hadron Physics group, which is a part of the BES III collaboration, is preparing a proposal for data taking for ΛΣ̄ 0 transition form factors and Σ 0 direct form factors at 2.5 GeV.Aiming the electromagnetic form factors of Σ hyperons, this work contributes to this proposal by simulation study of the e+ e− → ΛΣ̄ 0 and e + e − → Σ 0 Σ̄ 0 reactions. The efficiency and resolution of the electromagnetic calorimeter sub-detector of BES III and kinematic properties of the detected particles are studied in this work. Our final goal is to provide input for the beam time proposal and optimize the future measurement.In the first chapter, the theoretical background including the Standard Model, strong interaction, QCD, and hadrons are studied. In the second chapter, some concepts like the formalism of cross section, relativistic kinematics, and electromagnetic form factors are briefly presented. The third chapter is dedicated to introducing the e + e − → ΛΣ̄ 0 and e + e − → Σ 0 Σ̄ 0 reactions. The BES experiment at BEPC-II is introduced in chapter 4. In chapter 5, the software tools which have been used for this work are introduced. In the sixth chapter, the result of a toy-Monte Carlo study for parameter estimation is presented. The last chapter is dedicated to the results of a full BES software simulation.
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Bulala, Avuyile Sisanda. "Efficiency calibration of a gamma-ray detector for measuring environmental radiation." Master's thesis, University of Cape Town, 2020. http://hdl.handle.net/11427/32467.
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The Environmental Radioactivity Laboratory (ERL) of iThemba LABS conducts research into levels of natural and anthropogenic radioactivity in the environment. The laboratory-based measurements are conducted using a low-background Hyper Pure Germanium (HPGe) detector system. A critical aspect of such measurements involves calibrating the detector about energy and detection efficiency. The present study details experiment that were carried to determine both energy and efficiency calibrations for various sample geometries using gamma-ray spectrometry. The measurements using reference sources of known activity were carried out using two sample holders (Marinelli Beaker (1000 ml) and, a cylindrical pill bottle (100 ml)), and a point source. The IAEA reference materials (RGU-1, RGTh-1 ore and RGK-1) were prepared and used to fill the Marinelli beaker and pill bottles. Certified reference point sources (⁶⁰Co, ¹⁵²Eu, ¹³⁷Cs, ²²Na, ²⁴¹Am and ¹³³Ba) were obtained from the National Metrology Institute of South Africa (NMISA). Experiments consisted of exposing the HPGe detector to various gamma-ray sources prepared using various sample holders and the point source geometry. The counting time for each measurement was 24 hours. Each spectrum was analysed by inserting region of interests around suitably selected photo-peaks and the counts associated with these photo-peaks were automatically determined and corrected for background by the software. The full energy peak detection efficiency was then determined from the background corrected counts, the known activity of the source and the implicit in measurement (solid angle). The experimental and simulated spectra using point sources and volume sources were compared. Both experimental and simulated spectra presented showed a good agreement in terms of shape and varying intensities as expected. Additional photo-peaks were observed from ²²Na, ⁶⁰Co, ¹³³Ba and ¹⁵²Eu (point sources) and ²³²Th and ²³⁸U (volume sources) experimental spectra these effects were not observed in the simulated spectra. These additional peaks observed are the result of coincidence summing in some of gamma emitting radionuclides. Efficiencies that were experimentally determined, were compared with the calculated efficiencies from Monte Carlo simulations using MCNPX. Efficiency calibration parameters (power fit function) for the volume sources were determined from experimental and simulated data; a = 2.58; b = -0.75 experimental and a = 1.01; b = 0.65 simulated (100 mL pill bottle) and a = 2.07; b = -0.75 experimental and a = 1.61; b = 0.66 simulated (1 L Marinelli beaker). The simulated parameters for the efficiency as determined can be used for future calculations of activity concentrations when the 100 mL pill bottle or 1 L Marinelli Beaker sample holder is used. Further improvement in these calculations can be achieved by considering the sample density. The simulation input files used to generate these values is available and can be modified to match any sample holder geometry, as well as any density that might be required in future counting.
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Heikkilä, Annele. "Studies of Light Hyperon Decay Parameters." Thesis, Uppsala universitet, Kärnfysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-388602.
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A basic assumption in fundamental physics is that equal amounts of matter and antimatter were created after the Big Bang. When particles and antiparticles collide, they annihilate, i.e. disappear and produce photons. Nevertheless, the universe consists mainly of matter today. To explain why all matter did not disappear, violation of CP symmetry beyond the Standard Model is required. CP symmetry means that the laws of physics are the same if particles are interchanged with antiparticles and spatial coordinates of all particles are mirrored. CP symmetry is relatively poorly tested in baryon decays. A new method to study CP symmetry in hyperon-antihyperon pairs has been developed at Uppsala University. Hyperons are baryons with one or more strange quarks. The method allows determining the decay asymmetry parameters of the hyperon and antihyperon separately if the hyperon-antihyperon pair is polarized. If any significant difference between the magnitudes of these parameters is found, the process is CP violating. The particle physics experiment BESIII in China is a suitable experiment to conduct this kind of measurements because it is a high precision experiment and has collected large data samples of hyperon-antihyperon pairs. The goal of this project was to study statistical precisions of the physics parameters that can be obtained with the new method in cases of J/ψ meson decaying into ΛΛ, Σ+Σ− and Σ0Σ0. High statistical precision is required to detect CP violation, because CP violating processes are, if they exist, expected to be rare. The main focus was to study the process e+e− → J/ψ → Σ0Σ0 → ΛγΛγ → pπ−γpπ+γ. In this process, CP symmetry can be tested in two decay processes: electromagnetic decay Σ0 → Λγ and weak decay Λ → pπ−. Only the asymmetry parameter of Λ → pπ− was studied. The study served as a validity check of the new method and ongoing analyses at BESIII. The statistical precision was studied by simulations: Monte Carlo data samples were created and then a maximum-log-likelihood fit was applied to the samples. An important component when determining the asymmetry parameters turned out to be the relative phase ∆φJ/ψ. The relative phase is one of the parameters used for determining the relation between the electric and magnetic form factors. ∆φJ/ψ is also related to the polarization of the hyperon-antihyperon pair. The study showed that the value of ∆φJ/ψ has a large impact on the uncertainties of the hyperon and antihyperon asymmetry parameters. A low value of ∆φJ/ψ resulted in high uncertainties and strong correlations between the asymmetry parameters. The formalism is different for different processes, which affects the uncertainties as well. The formalism used for the Σ0Σ0 process gives poorer parameter precision of the asymmetry parameter related to the Λ → pπ− decay than the formalism used for the ΛΛ process. Therefore, the ΛΛ process is a much more suitable process for CP studies of the Λ → pπ− decay.Ett grundantagande inom den fundamentala fysiken är att lika stora mängder av materia och antimateria skapades efter Big Bang. När partiklar och antipartiklar kolliderar, annihilerar de, dvs försvinner och producerar fotoner. Trots detta består dagens universum huvudsakligen av materia. För att förklara varför all materia inte försvann krävs ett brott mot CP-symmetrin bakom standardmodellen. CP-symmetrin innebär att fysikens lagar är desamma om man byter partiklar mot antipartiklar och speglar partikelns rumsliga koordinater. CP-symmetri i baryonsönderfall är relativt dåligt testad. En ny metod för att studera CP-symmetrin har utvecklats vid Uppsala universitet för hyperon-antihyperon par. Hyperoner är baryoner med en eller fler särkvarkar. Metoden gör det möjligt att bestämma asymmetriparametrar hos hyperon- och antihyperonsönderfall separat om hyperonantihyperonparet är polariserat. Om en signifikant skillnad mellan värden av dessa parametrar upptäcks, är processen CP-brytande. Partikelfysikexperimentet BESIII i Kina är ett lämpligt experiment för sådana här mätningar eftersom det är ett högpresicionsexperiment och har dessutom samlat in stora mängder data av hyperon-antihyperonpar. Målet för detta projekt har varit att studera de statistiska precisioner av fysikparametrar som kan nås när man använder den nya metoden i de fall där J/ψ mesonen sönderfaller till ΛΛ, Σ+Σ− och Σ0Σ0. Hög statistisk precision behövs för att upptäcka CP-brott, eftersom CP-brytande processer, om de existerar, är relativt sällsynta. Huvudfokuset var att studera processen e+e− → J/ψ → Σ0Σ0 → ΛγΛγ → pπ−γpπ+γ. I denna process kan CP-symmetri testas för två sönderfallsprocesser: det elektromagnetiska sönderfallet Σ0 → Λγ och det svaga sönderfallet Λ → pπ−. I denna rapport studerades bara asymmetriparametrarna av Λ → pπ−. Detta arbete har fungerat som validitetskontroll av den nya metoden och pågående analyser på BESIII. Den statistiska precisionen undersöktes med simuleringar: Monte Carlo datamängder skapades och sedan en maximum-log-likelihood-anpassning av datan genomfördes. En viktig komponent i bestämningen av asymmetriparametrarna visade sig vara den relativa fasen, ∆φJ/ψ. Den relativa fasen är en av de parametrar som används för att bestämma relationen mellan de elektriska och magnetiska formfaktorer. ∆φJ/ψ är också relaterad till hyperonens hyperon-antihyperonparets polarisation. I forskningsprojektet visades att ∆φJ/ψ har en stor inverkan på osäkerheterna av hyperon- och antihyperonasymmetriparametrarna. Ett lågt värde av ∆φJ/ψ resulterade i stora osäkerheter och starka korrelationer mellan asymmetriparametrarna. Formalismen är annorlunda för olika processer, vilket också påverkar osäkerheterna. Formalismen som används för Σ0Σ0-processen ger sämre parameterprecision av asymmetriparametern kopplad till sönderfallet Λ → pπ− än formalismen som används för ΛΛ-processen. Därför är ΛΛ-processen en mycket lämpligare process för att testa CP-symmetrin i Λ → pπ− sönderfallet.
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Andrean, Stefio Yosse. "Search for Stop Using the ATLAS Detector and Performance Analysis of the Tile Calorimeter with Muons from W Decays." Licentiate thesis, Stockholms universitet, Fysikum, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-191555.
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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.
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El, Faham Hesham. "Phenomenological Studies on Composite Higgs Models." Thesis, Uppsala universitet, Högenergifysik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-359903.
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Composite Higgs Models (CHMs) are formulated in terms of strongly coupled theories. They often predict fermionic top partners with a mass around the TeV scale. Going beyond minimality enriches the spectrum of the theory with additional hypothetical scalars that significantly change the phenomenology. In this thesis, we explore an SO(6)/SO(5) CHM with an additional pseudo-scalar custodial singlet. The latter has anomalous couplings to the Standard Model vector bosons. We study the phenomenology of the singlet, including bounds from the available ATLAS and CMS searches in the relevant channels with di-boson and fermionic final states. We used HiggsBounds tool to test the model theoretical predictions against the current exclusion limits. The study is performed at the 8 and 13 TeV experiments at the LHC. We present a model parameter space from which the bounds on the (most sensitive) signal cross sections of the hypothetical singlet can be easily extracted.
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Chen-Lin, Xinyi. "Non-conformal gauge/string duality : A rigorous case study." Doctoral thesis, Uppsala universitet, Teoretisk fysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-321881.
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The gauge/string duality, a.k.a. the holographic principle is a profound assertion that emerged from string theory. It relates strongly-coupled gauge theories to weakly coupled string theories living in a higher-dimensional curved geometry. Nevertheless, it is a conjecture, and only a few instances of its more concrete form, the AdS/CFT correspondence, are well-understood. The most well-studied example is the duality between N=4 SYM, which is a CFT, and type IIB string theory in AdS5xS5 background. Generalization to less symmetric cases is a must, and the next logical step is to add a mass scale to N=4 SYM, therefore breaking its conformal symmetry and leading to N=2* SYM, the theory we study in this thesis. It is supersymmetric enough to employ the powerful localization method that reduces its partition function to a matrix model. We will see that the mass scale causes non-trivial phase structures in its vacuum configuration, visible in the holographic regime. We will probe them using Wilson loops in different representations of the gauge group. On the other hand, the dual supergravity background was derived by Pilch-Warner, making N=2* theory an explicitly testable non-conformal holographic case, which is a rare example. We will prove that the duality works for the dual observables (string action, D-branes) we managed to compute, even at a quantum-level.
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Eriksson, Jacob. "Fuel ion densities and distributions in fusion plasmas : Modeling and analysis for neutron emission spectrometry." Licentiate thesis, Uppsala universitet, Tillämpad kärnfysik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-192530.
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Neutrons produced in fusion reactions in a magnetically confined plasma carry information about the distributions and densities of the fuel ions in the plasma. This thesis presents work where various theoretical models of different fuel ion distributions in the plasma are used to calculate modeled components of the neutron energy spectrum. The calculated components can then be compared with measured data, either to benchmark and validate the model or to derive various plasma parameters from the experimental data. Neutron spectra measured with the spectrometers TOFOR and the MPR, which are both installed at the JET tokamak in England, are used for this purpose. The thesis is based on three papers. The first paper presents the analysis of TOFOR data from plasmas heated with neutral beams and radio frequency waves tuned to the third harmonic of the deuterium cyclotron frequency, which creates fast (supra thermal) ions in the MeV range. It is found that effects of the finite Larmor radii of the fast ions need to be included in the modeling in order to understand the data. These effects are important for fast ion measurements if there is a gradient in the fast ion distribution function with a scale length that is comparable to - or smaller than - the width of the field of view of the measuring instrument, and if this scale length is comparable to - or smaller than - the Larmor radii of the fast ions. The second paper presents calculations of the neutron energy spectrum from the T(t,n)4He reaction, for JET relevant fuel ion distributions. This is to to form a starting point for the investigation of the possibility to obtain fast ion information from the t-t neutron spectrum, in a possible future deuterium-tritium campaign at JET. The t-t spectrum is more challenging to analyze than the d-d and d-t cases, since this reaction has three (rather than two) particles in the final state, which results in a broad continuum of neutron energies rather than a peak. However, the presence of various final state interactions - in particular between the neutron and the 4He - might still allow for spectrometry analysis. Finally, in Paper III, a method to derive the fuel ion ratio, nt/nd, is presented and applied to MPR data from the JET d-t campaign in 1997. The trend in the results are consistent with Penning trap measurements of the fuel ion ratio at the plasma edge, but the absolute numbers are not the same. Measuring the fuel ion ratio in the core plasma is an important task for fusion research, and also a very complicated one. Future work should aim at measuring this quantity in several independent ways, which should then be cross checked against each other.
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Vaduret, Jean-François. "GPPZ and the Holographic Triforce against Scalars." Thesis, Uppsala universitet, Teoretisk fysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-397107.
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We use gauge-invariant cosmological perturbation theory to compute one-point functions of active and inert scalar fields of the GPPZ RG-flow in AdS5. Linearized Einstein equations are computed and made gauge-invariant for D-dimensional Euclidean domain-wall geometry. We briefly review the procedure of holographic renormalization for the GPPZ RG-flow in AdS5 to get different one-point functions. The source-dependant vev of the operator dual to the ∆ = 3 active scalar field in the GPPZ solution is computed and agrees with literature. We also find the source-dependant one-point function of the operator dual to the ∆ = 3 inert scalar.
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Carney, Rebecca. "Instrumentation for silicon tracking at the HL-LHC." Licentiate thesis, Stockholms universitet, Fysikum, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-144216.
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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.
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Sengupta, Rohini. "Long-Lived Particles at the FCC-ee." Thesis, Uppsala universitet, Tillämpad kärnfysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-444329.
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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.