arXiv subjects

N. Chikuma

Publications and source records attributed to N. Chikuma.

40 records · Page 3Linked to original sources

arXiv2015

Measurement of the muon neutrino inclusive charged-current cross section in the energy range of 1-3 GeV with the T2K INGRID detector

We report a measurement of the $ν_μ$-nucleus inclusive charged current cross section (=$σ^{cc}$) on iron using data from exposed to the J-PARC neutrino beam. The detector consists of 14 modules in total, which are spread over a range of off-axis angles from 0$^\circ$ to 1.1$^\circ$. The variation in the neutrino energy spectrum as a function of the off-axis angle, combined with event topology information, is used to calculate this cross section as a function of neutrino energy. The cross section is measured to be $σ^{cc}(1.1\text{ GeV}) = 1.10 \pm 0.15$ $(10^{-38}\text{cm}^2/\text{nucleon})$, $σ^{cc}(2.0\text{ GeV}) = 2.07 \pm 0.27$ $(10^{-38}\text{cm}^2/\text{nucleon})$, and $σ^{cc}(3.3\text{ GeV}) = 2.29 \pm 0.45$ $(10^{-38}\text{cm}^2/\text{nucleon})$, at energies of 1.1, 2.0, and 3.3 GeV, respectively. These results are consistent with the cross section calculated by the neutrino interaction generators currently used by T2K. More importantly, the method described here opens up a new way to determine the energy dependence of neutrino-nucleus cross sections.

hep-ex↗

arXiv2015

Measurement of the $ν_μ$ charged current quasi-elastic cross-section on carbon with the T2K on-axis neutrino beam

We report a measurement of the $ν_μ$ charged current quasi-elastic cross-sections on carbon in the T2K on-axis neutrino beam. The measured charged current quasi-elastic cross-sections on carbon at mean neutrino energies of 1.94 GeV and 0.93 GeV are $(11.95\pm 0.19(stat.)_{-1.47}^{+1.82} (syst.))\times 10^{-39}\mathrm{cm}^2/\mathrm{neutron}$ and $(10.64\pm 0.37(stat.)_{-1.65}^{+2.03} (syst.))\times 10^{-39}\mathrm{cm}^2/\mathrm{neutron}$, respectively. These results agree well with the predictions of neutrino interaction models. In addition, we investigated the effects of the nuclear model and the multi-nucleon interaction.

hep-ex↗

arXiv2015

Measurement of the Electron Neutrino Charged-current Interaction Rate on Water with the T2K ND280 pi-zero Detector

This paper presents a measurement of the charged current interaction rate of the electron neutrino beam component of the beam above $1.5$~GeV using the large fiducial mass of the T2K $π^0$ detector. The predominant poriton of the $ν_e$ flux ($\sim$85 %) at these energies comes from kaon decays. The measured ratio of the observed beam interaction rate to the predicted rate in the detector with water targets filled is 0.89 $\pm$ 0.08 (stat.) $\pm$ 0.11 (sys.), and with the water targets emptied is 0.90 $\pm$ 0.09 (stat.) $\pm$ 0.13 (sys.). The ratio obtained for the interactions on water only from an event subtraction method is 0.87 $\pm$ 0.33 (stat.) $\pm$ 0.21 (sys.). This is the first measurement of the interaction rate of electron neutrinos on water, which is particularly of interest to experiments with water Cherenkov detectors.

hep-ex↗

arXiv2015

Measurements of neutrino oscillation in appearance and disappearance channels by the T2K experiment with 6.6E20 protons on target

We report on measurements of neutrino oscillation using data from the T2K long-baseline neutrino experiment collected between 2010 and 2013. In an analysis of muon neutrino disappearance alone, we find the following estimates and 68% confidence intervals for the two possible mass hierarchies: Normal Hierarchy: $\sin^2θ_{23}=0.514^{+0.055}_{-0.056}$ and $Δm^2_{32}=(2.51\pm0.10)\times 10^{-3}$ eV$^2$/c$^4$ Inverted Hierarchy: $\sin^2θ_{23}=0.511\pm0.055$ and $Δm^2_{13}=(2.48\pm0.10)\times 10^{-3}$ eV$^2$/c$^4$ The analysis accounts for multi-nucleon mechanisms in neutrino interactions which were found to introduce negligible bias. We describe our first analyses that combine measurements of muon neutrino disappearance and electron neutrino appearance to estimate four oscillation parameters and the mass hierarchy. Frequentist and Bayesian intervals are presented for combinations of these parameters, with and without including recent reactor measurements. At 90% confidence level and including reactor measurements, we exclude the region: $δ_{CP}=[0.15,0.83]π$ for normal hierarchy and $δ_{CP}=[-0.08,1.09]π$ for inverted hierarchy. The T2K and reactor data weakly favor the normal hierarchy with a Bayes Factor of 2.2. The most probable values and 68% 1D credible intervals for the other oscillation parameters, when reactor data are included, are: $\sin^2θ_{23}=0.528^{+0.055}_{-0.038}$ and $|Δm^2_{32}|=(2.51\pm0.11)\times 10^{-3}$ eV$^2$/c$^4$.

hep-ex↗