This paper presents an extension of the MK single pion production model \cite{MK, MK2} to high hadron invariant mass (\(W\)) and high momentum transfer to conform to the predictions of perturbative ...QCD due to quark-hadron duality. New form factors for several resonant interactions and non-resonant background in the electron-nucleon cross-sections are determined taking into account the experimental data and improved evaluation techniques. Fits to electron-proton scattering data are used to calculate the vector-current form factors, and to assign uncertainties to the constrained free parameters of the model. The %hadron currents results from this work can be used to determine the vector current in the corresponding neutrino-nucleon cross-sections, which are an important input for event generators in long baseline neutrino oscillation measurements.
The T2K experiment presents new measurements of neutrino oscillation parameters using
protons on target (POT) in (anti-)neutrino mode at the far detector (FD). Compared to the previous analysis, an ...additional
POT neutrino data was collected at the FD. Significant improvements were made to the analysis methodology, with the near-detector analysis introducing new selections and using more than double the data. Additionally, this is the first T2K oscillation analysis to use NA61/SHINE data on a replica of the T2K target to tune the neutrino flux model, and the neutrino interaction model was improved to include new nuclear effects and calculations. Frequentist and Bayesian analyses are presented, including results on
and the impact of priors on the
measurement. Both analyses prefer the normal mass ordering and upper octant of
with a nearly maximally CP-violating phase. Assuming the normal ordering and using the constraint on
from reactors,
using Feldman-Cousins corrected intervals, and
using constant
intervals. The CP-violating phase is constrained to
using Feldman-Cousins corrected intervals, and
is excluded at more than 90% confidence level. A Jarlskog invariant of zero is excluded at more than
credible level using a flat prior in
and just below
using a flat prior in
When the external constraint on
is removed,
in agreement with measurements from reactor experiments. These results are consistent with previous T2K analyses.
This paper presents an update to the MK model, which was developed to describe single pion production in neutrino-nucleon interactions. Originally the MK model used the helicity amplitudes and the ...hadronic current form-factors of the Rein and Sehgal model. The update includes a new definition for the helicity amplitudes in the first and second resonance regions, and new vector-current form factors. Fits to electron-proton scattering data were used to determine these vector-current form factors, and to assign errors to the constrained free parameters of the model.
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