Narrow Results

We review the current-generation short-baseline reactor neutrino experiments that have firmly established the third neutrino mixing angle θ₁₃ to be nonzero. The relative large value of θ₁₃ (around 9°) has opened many new and exciting opportunities for future neutrino experiments. Daya Bay experiment with the first measurement of is aiming for a precision measurement of this atmospheric mass-squared splitting with a comparable precision as from accelerator muon neutrino experiments. JUNO, a next-generation reactor neutrino experiment, is targeting to determine the neutrino mass hierarchy (MH) with medium baselines (~ 50 km). Beside these opportunities enabled by the large θ₁₃, the current-generation (Daya Bay, Double Chooz, and RENO) and the next-generation (JUNO, RENO-50, and PROSPECT) reactor experiments, with their unprecedented statistics, are also leading the precision era of the three-flavor neutrino oscillation physics as well as constraining new physics beyond the neutrino Standard Model.

The MINOS experiment uses the NuMI ν_μ beam to make precise measurements of neutrino flavor oscillations in the "atmospheric" neutrino sector. MINOS can also probe the yet-unknown neutrino mixing angle θ₁₃ by searching for a ν_e appearance signal in the ν_μ beam. This paper reviews the techniques developed for the first ν_e appearance analysis in MINOS.

Neutrinos are elementary particles in the standard model of particle physics. There are three flavors of neutrinos that oscillate among themselves. Their oscillation can be described by a 3×3 unitary matrix, containing three mixing angles θ₁₂, θ₂₃, θ₁₃, and one CP phase. Both θ₁₂ and θ₂₃ are known from previous experiments. θ₁₃ was unknown just two years ago. The Daya Bay experiment gave the first definitive nonzero value in 2012. An improved measurement of the oscillation amplitude and the first direct measurement of the mass-squared difference were obtained recently. The large value of θ₁₃ boosts the next generation of reactor antineutrino experiments designed to determine the neutrino mass hierarchy, such as JUNO and RENO-50.

Experiments on neutrino oscillations have uncovered several small parameters, θ₁₃ being a prominent one. Others are the solar mass splitting vis-à-vis the atmospheric one and the deviation of θ₂₃ from maximal mixing. In this talk, (talk given at the International Conference on Massive Neutrinos, Singapore, 9–13 February 2015) we elaborate on a neutrino mass model based on the see-saw mechanism in which the mixing angles to start with are either vanishing (θ₁₃ and θ₁₂) or π/4 (θ₂₃). The atmospheric mass splitting is taken as a part of this initial structure but the solar splitting is absent. A perturbative contribution, originating from a Type-I see-saw, results in nonzero values of θ₁₃, θ₁₂, , and shifts θ₂₃ slightly from π/4, interrelating them all. The model incorporates CP-violation, the phase δ being close to 3π/2 for (a) quasidegeneracy or (b) inverted mass ordering. It will be put to test as the neutrino parameters get better determined.

Neutrinos are elementary particles in the standard model of particle physics. There are three flavors of neutrinos that oscillate among themselves. Their oscillation can be described by a 3×3 unitary matrix, containing three mixing angles θ₁₂, θ₂₃, θ₁₃, and one CP phase. Both θ₁₂ and θ₂₃ are known from previous experiments. θ₁₃ was unknown just two years ago. The Daya Bay experiment gave the first definitive non-zero value in 2012. An improved measurement of the oscillation amplitude and the first direct measurement of the mass-squared difference were obtained recently. The large value of θ₁₃ boosts the next generation of reactor antineutrino experiments designed to determine the neutrino mass hierarchy, such as JUNO and RENO-50.

Experiments on neutrino oscillations have uncovered several small parameters, θ₁₃ being a prominent one. Others are the solar mass splitting vis-à-vis the atmospheric one and the deviation of θ₂₃ from maximal mixing. In this talk, we elaborate on a neutrino mass model based on the see-saw mechanism in which the mixing angles to start with are either vanishing (θ₁₃ and θ₁₂) or π/4 (θ₂₃). The atmospheric mass splitting is taken as a part of this initial structure but the solar splitting is absent. A perturbative contribution, originating from a Type-I see-saw, results in nonzero values of θ₁₃, θ₁₂, , and shifts θ₂₃ slightly from π/4, interrelating them all. The model incorporates CP-violation, the phase δ being close to 3π/2 for (a) quasidegeneracy or (b) inverted mass ordering. It will be put to test as the neutrino parameters get better determined.