Supersymmetric Standard Model has been built to solve the hierarchy problem which is encountered whenever Standard Model is incorporated into a theory with a larger mass scale. Experimentally, one of the first signals of physics beyond Standard Model is provided by the atmospheric neutrino experiments which indicate the existence of at least one non-zero neutrino mass. An interpretation of both solar and atmospheric neutrino anomalies in terms of neutrino oscillations would lead to specific patterns for neutrino masses and mixing. In this thesis, we studied the possibilities of generating the required neutrino mass patterns in the context of supersymmetric standard models with lepton number (L) violation. After an introduction to supersymmetric standard models in Chapter 1, we give an overview of neutrino phenomenology in chapter 2. Chapter 3 discusses analytical and semi-analytical solutions to Renormalisation Group Equations (RGE) with lepton number violating couplings in the superpotential. Neutrino masses with bilinear L violation in the context of gauge mediated supersymmetric models (GMSB) are discussed in Chapter 4, where 2-loop RGE for the parameter $\Delta B_i$ are presented. Chapter 5 discusses neutrino mass structure when L violation is through trilinear lepton number violating terms. Chapter 6 discusses RG enhancement of neutrino masses and neutrino mass bounds on trilinear lepton number violating couplings in the context of mSUGRA. Chapter 7 summarises general features of neutrino masses within these models and contains overall conclusions based on the work presented in the thesis.

The landmark discovery that neutrinos have mass and can change type (or flavour) as they propagate-a process called neutrino oscillation^1-6-has opened up a rich array of theoretical and experimental questions being actively pursued today. Neutrino oscillation remains the most powerful experimental tool for addressing many of these questions, including whether neutrinos violate charge-parity (CP) symmetry, which has possible connections to the unexplained preponderance of matter over antimatter in the Universe^7-11. Oscillation measurements also probe the mass-squared differences between the different neutrino mass states (Δm²), whether there are two light states and a heavier one (normal ordering) or vice versa (inverted ordering), and the structure of neutrino mass and flavour mixing¹². Here we carry out the first joint analysis of datasets from NOvA¹³ and T2K¹⁴, the two currently operating long-baseline neutrino oscillation experiments (hundreds of kilometres of neutrino travel distance), taking advantage of our complementary experimental designs and setting new constraints on several neutrino sector parameters. This analysis provides new precision on the Δm322 mass difference, finding 2.43-0.03+0.04×10-3eV2 in the normal ordering and -2.48-0.04+0.03×10-3eV2 in the inverted ordering, as well as a 3σ interval on δ_CP of [-1.38π, 0.30π] in the normal ordering and [-0.92π, -0.04π] in the inverted ordering. The data show no strong preference for either mass ordering, but notably, if inverted ordering were assumed true within the three-flavour mixing model, then our results would provide evidence of CP symmetry violation in the lepton sector.

In the current standard model of particle physics, neutrinos are massless and strictly left-chiral. With neutrino oscillations definitively observed, we know experimentally that neutrinos have non-zero mass. The standard model for leptons, including the Higgs mechanism for mass generation will be explored. Extensions to the standard model to give neutrinos mass and the so called see-saw mechanism will then be presented. Finally, one model of the see-saw mechanism purposed by S. F. King will then be compared to recent data from the T2K experiment. (Master of Science (M.S.), Physics, Colorado St

For decades, the Standard Model of Particle Physics has stood the test of time, being one of the most comprehensive and reliable models ever proposed. One of the few exceptions to its robustness was the discovery of neutrino oscillations (and consequently the implication that neutrinos have mass). It is one of the only confirmed pieces of evidence of physics beyond the Standard Model. Since this discovery, there has been a worldwide effort on both the theoretical and experimental fronts to answer many questions that this discovery raised. Many neutrino experiments around the world seek to meas

This thesis is devoted to the study of neutrino physics in general and the study of neutrino mixing and oscillations in particular. In the standard model of particle physics, neutrinos are massless, and as a result, they do not mix or oscillate. However, many experimental results now seem to give evidence for neutrino oscillations, and thus, the standard model has to be extended in order to incorporate neutrino masses and mixing among different neutrino flavors. When neutrinos propagate through matter, the neutrino mixing, and thus, also the neutrino oscillations, may be significantly altered.

Neutrino oscillations are clear evidence for physics beyond the standard model. The goal of next-generation neutrino oscillation experiments is to find a non-zero $\theta_{13}$, the last mixing matrix element for which we only know an upper limit. For this, next-generation long-baseline neutrino oscillation experiments require an order of magnitude better sensitivities. In particular, accelerator-based experiments such as T2K and NOvA experiments need (1) good neutrino energy reconstruction for the precise measurement of $\Delta m^2_{32}$ and $sin^22\theta_{23}$, and (2) good background prediction to measure $\nu_e$ appearance signals. Current and near future high statistics neutrino experiments, such as K2K, MiniBooNE, SciBooNE, MINOS, and MINERvA help both (1) and (2) by precise signal and background channel measurements.

Recent developments in neutrino physics, primarily the demonstration of neutrino oscillations in both atmospheric neutrinos and solar neutrinos, provide the first conclusive evidence for physics beyond the Standard Model of particle physics. The simplest phenomenology of neutrino oscillations, for three generations of neutrino, requires six parameters — two squared mass differences, 3 mixing angles and a complex phase that could, if not 0 or π, contribute to the otherwise unexplained baryon asymmetry observed in the universe. Exploring the neutrino sector will require very intense beams of neutrinos, and will need novel solutions.

Neutrino oscillations are a phenomenon that has been observed for over two decades and leads to the conclusion that neutrinos have mass. The Standard Model predicts massless neutrinos, and so neutrinos require physics beyond the Standard Model. Other signatures of BSM physics are detectable in modern neutrino facilities -- this chapter explores those possibilities. These can range from new effects modifying neutrino oscillations (beyond the expectations when neutrinos have mass), to searches for new particles in neutrino facilities. Next-generation experiments are particularly powerful for these searches due to high-intensity neutrino beams and novel detection technologies. We give an introduction to these search strategies, giving a non-comprehensive overview of the field as it stands presently.

The study of neutrino oscillations is a main priority for particle physics as the most immediately tractable lever on physics beyond the Standard Model. In particular, more insight into violation of the combined symmetry of charge-conjugation plus parity could yield clues to the origin of matter-antimatter asymmetry, and in some theoretical frameworks the neutrino mass could give insights into dark matter. NOvA is a long-baseline accelerator neutrino experiment with both a near and far detector that seeks to measure several of the parameters of the neutrino mixing matrix, as well as carry out a broad program of additional physics. NOvA has innovated and developed a variety of techniques in the space of neutrino physics, including expanding the use of machine learning techniques in reconstruction. NOvA has also set the stage for the next generation US-based long baseline experiment, DUNE. This dissertation details the creation of a new neutrino interaction vertex reconstruction package for NOvA, which offers enormous improvements in accuracy above the previous vertexer it replaces. This is accomplished using a Convolutional Visual Network trained on large datasets of simulated events. The vertexer is validated thoroughly against data. This dissertation also presents a cross-section measurement for $\nu_\mu + N \rightarrow \mu^- + 1\pi^\pm + X$ (where X does not include additional charged pions) binned in pion kinetic energy, a challenging measurement in general and for NOvA in

of the process can shed light on several properties of the neutrino. In particular, it implies that the neutrino has a non-zero mass, which requires a Neutrino oscillation is a quantum mechanical phenomenon in which a neutrino created with a specific lepton family number ("lepton flavor": electron, muon, or tau) can later be measured to have a different lepton family number. The probability of measuring a particular flavor for a neutrino varies between three known states as it propagates through space. First predicted by Bruno Pontecorvo in 1957 Neutrino oscillation is a quantum mechanical phenomenon in which a neutrino created with a specific lepton family number ("lepton flavor": electron, muon, or tau) can later be measured to have a different lepton family number. The probability of measuring a particular flavor for a neutrino varies between three known states as it propagates through space. First predicted by Bruno Pontecorvo in 1957, neutrino oscillation has since been observed by a multitude of experiments in several different contexts. Most notably, the existence of neutrino oscillation resolved the long-standing solar neutrino problem. Neutrino oscillation is of great theoretical and experimental interest, as the precise properties of the process can shed light on several properties of the neutrino. In particular, it implies that the neutrino has a non-zero mass, which requires a modification to the Standard Model of particle physics. The experimental discovery of neutrino oscillation, and thus neutrino mass, by the Super-Kamiokande Observatory and the Sudbury Neutrino Observatories was recognized with the 2015 Nobel Prize for Physics.