arXiv subjects

Son Cao

Publications and source records attributed to Son Cao.

7 recordsLinked to original sources

arXiv2025

Disentangling data contributions to the precision measurement of the largest leptonic mixing angle

This study examines the precise measurement of the largest leptonic mixing angle $θ_{23}$ through the analysis of neutrino oscillation data samples. Our findings indicate that, contrary to common understanding, the $ν_μ(\barν_μ)\rightarrow ν_{e}(\barν_{e})$ appearance samples, rather than the $ν_μ(\barν_μ)\rightarrow ν_μ(\barν_μ)$ disappearance samples, are sensitive to test the hypothesis of maximal mixing $θ_{23}=π/4$, particularly if $θ_{23}$ resides in the higher octant and $\sin^2θ_{23}<0.54$. The former serves as the primary source for determining the octant of the $θ_{23}$ mixing angle; however, the latter remains relevant if $θ_{23}$ is indeed in the lower octant with $\sin^2θ_{23}<0.42$. In a joint T2HK and DUNE analysis, utilizing only appearance sub-samples can exclude the maximal-mixing and determine the actual octant for about 60\% of the currently allowed range of the $θ_{23}$ angle. We argue that, despite the presence of parameter degeneracy, the precise measurement of $θ_{23}$ exhibits minimal dependence on other unknown factors, including the CP-violation phase and neutrino mass ordering.

hep-ph↗

arXiv2024

On Precision of the Leptonic Mixing Angle $θ_{23}$ and its Implications for the Flavor Models

Among three leptonic mixing angles, $θ_{23}$ angle, which characterizes the fractional contribution of two flavor eigenstates $ν_μ$ and $ν_τ$ to the third mass eigenstate $ν_3$, is known to be the largest but the least precisely measured. The work investigates possible reach of $θ_{23}$ precision with two upcoming gigantic accelerator-based long-baseline neutrino experiments, namely Hyper-Kamiokande and DUNE experiments as well as a possible joint analyses of future neutrino facilities. Our simulation yields that each experiment will definitely establish the octant of $θ_{23}$ angle for all values within 1$σ$ parameter interval, while considering the current limitation. However, if the actual value is $0.48\leq \sin^2θ_{23}\leq 0.54$, it becomes challenging for these two experiments to reject the maximal ($θ_{23}=π/4$) hypothesis and conclude its octant. This octant-blind region can be further explored with the proposed facilities ESSnuSB and a neutrino factory. Accurate determination of the mixing angle $θ_{23}$, as well as the accuracy of $δ_{CP}$, is crucial for examining a certain category of discrete non-Abelian leptonic flavor models. Specifically if CP is conserved in leptonic sector, the combined analysis of Hyper-K and DUNE will rule out the majority of these models. However, if the CP is maximally violated, higher precision of $δ_{CP}$ is necessary for testing these flavor models.

hep-ph↗

arXiv2024

Develop monitors for MW-power proton beam at J-PARC extraction beamline for neutrino experiments

Intense and well-characterized neutrino sources, coupled with large and high-performance detectors, are essential for elucidating the unknowns in leptonic mixing through neutrino oscillation measurements. The J-PARC accelerator and neutrino extraction beamline have recently undergone upgrades, successfully delivering an 800-kW beam. We discuss the development, recent findings, and outstanding challenges associated with a non-destructive beam-induced fluorescence monitor and optical-fiber-based beam loss monitors.

hep-ex↗

arXiv2024

Scalable DAQ system operating the CHIPS-5 neutrino detector

The CHIPS R&D project focuses on development of low-cost water Cherenkov neutrino detectors through novel design strategies and resourceful engineering. This work presents an end-to-end DAQ solution intended for a recent 5 kt CHIPS prototype, which is largely based on affordable mass-produced components. Much like the detector itself, the presented instrumentation is composed of modular arrays that can be scaled up and easily serviced. A single such array can carry up to 30 photomultiplier tubes (PMTs) accompanied by electronics that generate high voltage in-situ and deliver time resolution of up to 0.69 ns. In addition, the technology is compatible with the White Rabbit timing system, which can synchronize its elements to within 100 ps. While deployment issues did not permit the presented DAQ system to operate beyond initial evaluation, the presented hardware and software successfully passed numerous commissioning tests that demonstrated their viability for use in a large-scale neutrino detector, instrumented with thousands of PMTs.

physics.ins-det↗

arXiv2023

Long Baseline Neutrino Oscillation Results (T2K and NOvA)

The well-established neutrino oscillation phenomenon, which confirms neutrinos have mass and the charged and neutral leptons are mixed, has been widely exploited to investigate the physics of this elusive particle. The complete description of neutrino oscillations, which are dictated by two mass-squared splittings, three mixing angles, and one Dirac CP-violation phase, however, has yet to be reached. The ongoing accelerator-based long-baseline neutrino experiments, T2K and NOvA, are critical in completing this picture. Using data and analyses accessible by summer 2023, T2K favors a leptonic CP violation at more than 90\% C.L. while NOvA shows no preference of this indication. Both experiments weakly opt for the \emph{normal} neutrino mass ordering and higher octant of the $θ_{23}$ mixing angle.

hep-ex↗

arXiv2022

Practical use of reactor anti-neutrinos for nuclear safeguard in Vietnam

One of the most abundant man-made sources of low energy (few~MeVs) neutrinos, reactor neutrino, is not only useful for studying neutrino properties, but it is also used in practical applications. In this study, we investigate the practical use of reactor neutrino detectors for nuclear safeguard in Vietnam, specifically at the Dalat Nuclear Reactor, a future research facility, and presumably commercial reactors with 500~kW, 10~MW, and 1000~MW thermal powers, respectively. We compute the rate of observed inverted beta decay events, as well as the statistical significance of extracting isotope composition under the practical assumptions of detector mass, detection efficiency, and background level. We find that a 1-ton detector mass can allow us to detect the reactor's on-off transition state from a few hours to a few days, depending on the standoff distance and reactor thermal power. We investigate how background and energy resolution affect the precision of the extracted weapon-usable ${}^{239}\text{Pu}$ isotope. We conclude that in order to distinguish the 10\% variation of the ${}^{239}\text{Pu}$ in the 10~MW thermal power reactor, a 1-ton detector placed 50~m away must achieve 1\% background level. Increasing the statistics by using a 10x larger detector or placing it $\sqrt{10}$ times closer to the reactor alleviates the requirement of the background level to 10\%.

hep-ex↗

arXiv2021

Neutrino mass spectrum: Present indication and future prospect

The fact that neutrinos are massive has been the most crucial evidence of physics beyond the Standard Model of elementary particles. To date, we still do not know how neutrinos get mass and why their mass is much smaller than that of their charged fermion cousins. The precise determination of the neutrino mass spectrum has become one of the central tasks of neutrino physics, providing critical input for understanding the nature of neutrino mass and extending our model. The present landscape of the neutrino mass spectrum is reviewed and explored in this article using data from the neutrino oscillation, cosmology, and beta decay. In addition, we discuss the possibility of relevant programs elucidating the neutrino mass spectrum in the coming decades.

hep-ph↗