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

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 σ$_{prod}$ = 227.6 ± 0.8(stat)$\frac{+1.9}{−3.2}$(sys) − 0.8(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.