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J. G. Walsh

Publications and source records attributed to J. G. Walsh.

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Electron Scattering and Neutrino Physics

A thorough understanding of neutrino-nucleus scattering physics is crucial for the successful execution of the entire US neutrino physics program. Neutrino-nucleus interaction constitutes one of the biggest systematic uncertainties in neutrino experiments - both at intermediate energies affecting long-baseline Deep Underground Neutrino Experiment (DUNE), as well as at low energies affecting coherent scattering neutrino program - and could well be the difference between achieving or missing discovery level precision. To this end, electron-nucleus scattering experiments provide vital information to test, assess and validate different nuclear models and event generators intended to be used in neutrino experiments. In this white paper, we highlight connections between electron- and neutrino-nucleus scattering physics at energies ranging from 10s of MeV to a few GeV, review the status of ongoing and planned electron scattering experiments, identify gaps, and layout a path forward that benefits the neutrino community. We also highlight the systemic challenges with respect to the divide between the nuclear and high-energy physics communities and funding that presents additional hurdle in mobilizing these connections to the benefit of neutrino programs.

hep-ex

CP-violation search with T2K data

The T2K experiment is a long-baseline neutrino oscillation experiment which uses $ν_μ$ and $\barν_μ$ beams to constrain CP-violating effects in a 3-flavor PMNS neutrino mixing model. Through $ν_μ\toν_{e}$ and $\barν_μ\to\barν_{e}$ appearance channels, T2K is sensitive to CP-violating effects in neutrino mixing. An excess of $ν_{e}$ candidates in the $ν$-beam mode is observed when compared to the CP conserving cases. T2K finds a best fit value of $δ_{\mathrm{CP}}=-1.97_{-0.70}^{+0.97}$ using Feldman-Cousins corrected intervals and excludes CP-conserving values of $δ_{\mathrm{CP}}$ of $0$ and $π$ at the 90% CL. $J_{\mathrm{CP}}=0$ is also excluded at 2$σ$ when using a flat prior in $δ_{\mathrm{CP}}$, favoring negative values.

hep-ex