Search for neutrinos from the Sun

Detection of the free neutrino: A Confirmation

Measurement of atmospheric neutrino oscillation parameters by Super-Kamiokande I

Results are reported from an improved measurement of ν_μ→ν_e transitions by the NOvA experiment. Using an exposure equivalent to 6.05×10^(20) protons on target, 33 ν_e candidates are observed with a background of 8.2±0.8 (syst.). Combined with the latest NOvA ν_μ disappearance data and external constraints from reactor experiments on sin^2 2θ_(13), the hypothesis of inverted mass hierarchy with θ_(23) in the lower octant is disfavored at greater than 93% C.L. for all values of δ_(CP).

Constraints on Oscillation Parameters from ν_e Appearance and ν_μ Disappearance in NOvA

NOvA is a long-baseline neutrino oscillation experiment, which consists of two finely-segmented liquid-scintillator detectors operating 14 mrad off-axis from the NuMI muon neutrino beam. With an 810 km baseline, the combined measurements of muon neutrino disappearance and electron neutrino appearance allow the determination of neutrino oscillation unknowns, namely the mass hierarchy, the octant of the largest neutrino mixing angle, and the CP violating phase. In this dissertation I present the joint analysis of νμ → νμ and νμ → νe oscillation data with an exposure of 8.85× 1020 protons on target on the 14 kton detector. It includes the estimation of neutrino energy distributions in the far detector using near detector data constraints, details of the implementation of the simultaneous fit of νμ and νe samples, and the effect of systematic uncertainties on the measurement of oscillation parameters. I also discuss NOvA’s projected sensitivity to determine the mass hierarchy and discover CP violation in future analyses with increased exposure and the addition of antineutrino datasets. With 66 electron neutrino and 126 muon neutrino candidates, the best fit to the data corresponds to the normal mass hierarchy, ∆m32 =2.44×10−3eV 2/c4, sin θ23 = 0.56, and δCP = 1.21π, with the allowed regions ∆m32 ∈ [2.37, 2.52]×10−3eV 2/c4, sin θ23 ∈ [0.43, 0.51]∪ [0.52, 0.60] and δCP ∈ [0, 0.12π] ∪ [0.91π, 2π] at the 68.3% C.L. Our data disfavor maximal mixing by 0.8σ, δCP = π/2 in the inverted hierarchy at higher than 3σ, and the entire inverted mass hierarchy at the 95% confidence level. By increasing the size of the samples and adding anti-neutrino data, NOvA can potentially resolve the neutrino mass hierarchy at 4σ C.L. or higher for some combinations of oscillation parameters. Improvements to the sensitivity to the determination of the mass hierarchy and CP violation in the neutrino sector can be achieved through gains in the NuMI beam intensity, the inclusion of external data, and refinements in the analysis methodology.

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Constraints on neutrino oscillation parameters with the NOvA experiment

aNOvA is a long-baseline neutrino oscillation experiment that uses the NuMI beam from Fermilab. Its physics goals include providing constraints to the neutrino mass hierarchy and the CP-violating phase $\delta$ by precision measurements of the electron (anti)neutrino appearance in a muon (anti)neutrino beam. Similarly, new limits on the values of $\sin^2{\theta_{23}}$ and $\Delta m^{2}_{32}$ will be achieved by measurements of the muon (anti)neutrino disappearance probabilities. A combined analysis measurement will allow a better resolution of the $\theta_{23}$ octant. The NuMI beam is produced by the collision of high energy protons into a target, giving rise to kaon and pion mesons that decay to neutrinos of a specific flavor. This thesis presents a measurement of the kaon production normalization scale using uncontained charged-current muon neutrinos at the Far Detector. Because the neutrino beam is not pure in flavor, it contains an admixture of other different n eutrino flavors that become a source of background. %in oscillation analysis. Therefore, it is of paramount importance for accelerator experiments, such as NOvA, to have a reliable flux prediction of the neutrino beam in order to achieve its physics goals. One method to constrain the flux is to constrain and measure each flux component independently. The kaon component contributes to the intrinsic $\nu_{e}$ contamination of the beam, a key background for the $\nu_{e}$-appearance analysis. We observed that the uncontained sample in the 10-20 GeV region corresponds to the kaon component of the NuMI beam at the Far Detector. We also found a 60-80\% correlation between the Near Detector $\nu_{e}$ background and the Far Detector $\nu_{\mu}$ uncontained signal. The data used for this analysis was collected from October 2014 to February 2017, corresponding to $7.99 \times 10^{20}$ protons-on-target (POT). The ratio between the Far Detector data and the simulation is fitted to a lin e in the 10-20 GeV energy region. Calibration, energy scale,! final state interactions and neutrino flux (e.g. beam transport and hadron production shape only) systematic uncertainties are considered. The kaon production normalization scale is measured to be $S_{K} = 1.07 \pm 0.16$.

Measurement of the kaon production normalization in the NuMI target using uncontained charged-current muon neutrino interactions in the NOvA Far Detector

Jose Andres Sepulveda-Quiroz

Papers

Measurement of the kaon production normalization in the NuMI target using uncontained charged-current muon neutrino interactions in the NOvA Far Detector