# Measurement of $\bar{\nu}_{\mu}$ and $\nu_{\mu}$ charged current inclusive cross sections and their ratio with the T2K off-axis near detector

## TL;DR

This paper reports the first measurements of muon neutrino and antineutrino charged current inclusive cross sections and their ratio at energies below 1.5 GeV using the T2K off-axis near detector, providing key data for neutrino interaction models.

## Contribution

The study presents the first measurements of $ar{
u}_{ ext{mu}}$ cross section and their ratio to $
u_{ ext{mu}}$ cross section at low energies, using the T2K off-axis near detector.

## Key findings

- Measured $ar{
u}_{ ext{mu}}$ cross section: (0.900 ± 0.029 (stat.) ± 0.088 (syst.))×10^{-39} cm^2/nucleon.
- Measured $
u_{ ext{mu}}$ cross section: (2.41 ± 0.022 (stat.) ± 0.231 (syst.))×10^{-39} cm^2/nucleon.
- Ratio $R(rac{ar{
u}}{
u})$ = 0.373 ± 0.012 (stat.) ± 0.015 (syst.)

## Abstract

We report a measurement of cross section $\sigma(\nu_{\mu}+{\rm nucleus}\rightarrow\mu^{-}+X)$ and the first measurements of the cross section $\sigma(\bar{\nu}_{\mu}+{\rm nucleus}\rightarrow\mu^{+}+X)$ and their ratio $R(\frac{\sigma(\bar \nu)}{\sigma(\nu)})$ at (anti-)neutrino energies below 1.5 GeV. We determine the single momentum bin cross section measurements, averaged over the T2K $\bar{\nu}/\nu$-flux, for the detector target material (mainly Carbon, Oxygen, Hydrogen and Copper) with phase space restricted laboratory frame kinematics of $\theta_{\mu}<32^\circ$ and $p_{\mu}>$500 MeV/c. The results are $\sigma(\bar{\nu})=\left( 0.900\pm0.029{\rm (stat.)}\pm0.088{\rm (syst.)}\right)\times10^{-39}$ and $\sigma(\nu)=\left( 2.41\ \pm0.022{\rm{(stat.)}}\pm0.231{\rm (syst.)}\ \right)\times10^{-39}$ in units of cm$^{2}$/nucleon and $R\left(\frac{\sigma(\bar{\nu})}{\sigma(\nu)}\right)= 0.373\pm0.012{\rm (stat.)}\pm0.015{\rm (syst.)}$.