Measurement of the production cross section of 31 GeV/$c$ protons on carbon via beam attenuation in a 90-cm-long target

TL;DR

This paper reports a precise measurement of the proton production cross section on carbon at 31 GeV/c using beam attenuation, reducing uncertainties in neutrino flux predictions for the T2K experiment.

Contribution

It introduces a direct measurement method for production cross sections that minimizes model corrections, improving precision over previous results.

Findings

Measured cross section: 227.6 mb with less than 2% total uncertainty.

Results agree with previous measurements but with higher precision.

Provides data to refine neutrino flux models for T2K.

Abstract

The production cross section of 30.92 GeV/$c$ protons on carbon is measured by the NA61/SHINE spectrometer at the CERN SPS by means of beam attenuation in a copy (replica) of the 90-cm-long target of the T2K neutrino oscillation experiment. The employed method for direct production cross-section estimation minimizes model corrections for elastic and quasi-elastic interactions. The obtained production cross section is $\sigma_\mathrm{prod}~=~227.6~\pm~0.8\mathrm{(stat)}~_{-~3.2}^{+~1.9}\mathrm{(sys)}~{-~0.8}\mathrm{(mod)}$ mb. It is in agreement with previous NA61/SHINE results obtained with a thin carbon target, while providing improved precision with a total fractional uncertainty of less than 2$\%$. This direct measurement is performed to reduce the uncertainty on the T2K neutrino flux prediction associated with the re-weighting of the interaction rate of neutrino-yielding hadrons.