Abstract

Polarization transfer (PT) observables in the single pion production induced by the charged current interaction of the neutrino with the nucleon are examined. The polarization components of the final nucleon and the charged lepton are calculated within two models for the pion production. The predictions are made for neutrino energy of the order of 1~GeV as well as for the T2K energy distribution. It is demonstrated that the PT observables, the degree of polarization and the polarization components of outgoing fermions, are sensitive on assumptions about the nonresonant background model. In particular it is shown that the normal components of the polarization of the outgoing nucleon and the lepton are determined by the interference between the resonant (RES) and nonresonant (NB) amplitudes. Moreover the sign of the normal component of the polarization of the charged lepton is fixed by the relative sign between the RES and the NB amplitudes.

Highlights

  • The first theoretical studies of the single pion production (SPP) in neutrino-nucleon scattering were performed more than 40 years ago

  • The measurement of the neutrino oscillation parameters and extraction of the CP-violation phase are made based on the analysis of the quasielastic (QE) neutrino-nucleus scattering; the SPP processes contribute to the background for the detection of the QE-like events as well as the electron neutrinos in the far detector

  • In particular we demonstrate that the investigation of the normal polarization components of the charged lepton and the final nucleon give knowledge about the relations between the RES

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Summary

INTRODUCTION

The first theoretical studies of the single pion production (SPP) in neutrino-nucleon (νN) scattering were performed more than 40 years ago. The ratio GpE=GpM obtained from the PT data turned out to be inconsistent with the Rosenbluth measurements It triggered off more detailed experimental and theoretical studies of the elastic electron-nucleon scattering. We investigate the polarization properties of the final nucleon produced in the SPP process This problem has been not studied before. In order to study the model dependence of the predictions of the PT observables, we consider two phenomenological approaches for the SPP: the Hernandez-Nieves-Valverde (HNV) model as formulated in [8] and the Fogli-Nardulli (FN) model as described in [11] Both approaches are similar in construction but it is demonstrated that small differences in the treatment of the NB contribution give rise to disparities in the predictions of the PT observables.

KINEMATICS AND CROSS SECTION
POLARIZATION TRANSFER OBSERVABLES
SPP MODELS
HNV model
Δð1232Þ contribution
Fogli-Nardulli model
Unpolarized cross sections
E-4 2 E-4 2 E-4 2 E-4 1 E-4 5 E-5 0 E0
Polarization transfer observables
FN model
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