T2K is a long baseline neutrino oscillation experiment, located in Japan. A muon (anti)neutrino beam peaked at 0.6 GeV is produced in the J-PARC facility and measured by near detectors and the Super-Kamiokande far detector. The main goal is to measure the neutrino oscillation parameters. T2K can run in both neutrino and antineutrino mode, enhancing the sensitivity to charge-parity violation (CPV) in the lepton sector. Measuring oscillation parameters requires precise knowledge of the (anti)neutrino interaction cross sections.
We present a novel analysis using the two T2K near detectors, INGRID and ND280, to provide a world-leading measurement of the charged-current meson-less neutrino and antineutrino interaction cross sections. For the first time, this analysis utilizes combined data samples of multiple detectors and multiple beam configurations. This technique fully exploits the correlations between the samples' systematic uncertainties, allowing for their efficient cancellation.
As INGRID and ND280 sample different neutrino energy spectra, due to the former being located on the same axis as the beam and the latter being off-axis, this measurement will allow for a better understanding of the energy dependence of neutrino interactions, thereby offering a direct probe of the processes that are responsible for the largest systematic uncertainties in T2K oscillation analyses. In addition, by measuring both neutrino and antineutrino cross sections, we can better tune theoretical models of nuclear effects such as multinucleon interactions. As CPV experiments measure the asymmetry between neutrino and antineutrino oscillation rates, the interaction asymmetry between the two must be understood properly and is of fundamental importance to avoid degeneracies.