Measurements of ${\bar{\nu }}_{\mu }$ and ${\bar{\nu }}_{\mu }+{\nu }_{\mu }$ charged-current cross-sections without detected pions nor protons on water and hydrocarbon at mean antineutrino energy of 0.86 GeV

Abstract

We report measurements of the flux-integrated ${\bar{\nu }}_{\mu }$ and ${\bar{\nu }}_{\mu }+{\nu }_{\mu }$ charged-current cross-sections on water and hydrocarbon targets using the T2K anti-neutrino beam, with a mean neutrino energy of 0.86 GeV. The signal is defined as the (anti-)neutrino charged-current interaction with one induced ${\mu }^{\pm }$ and no detected charged pion nor proton. These measurements are performed using a new WAGASCI module recently added to the T2K setup in combination with the INGRID Proton module. The phase space of muons is restricted to the high-detection efficiency region, $p_{\mu }>400\mathrm{MeV}/c$ and ${\theta }_{\mu }<30^{\circ }$, in the laboratory frame. Absence of pions and protons in the detectable phase space of "$p_{\pi }>200\mathrm{MeV}/c$ and ${\theta }_{\pi }<70^{\circ }$", and "$p_{\mathrm{p}}>600\mathrm{MeV}/c$ and ${\theta }_{\mathrm{p}}<70^{\circ }$" is required. In this paper, both of the ${\bar{\nu }}_{\mu }$ cross-sections and ${\bar{\nu }}_{\mu }+{\nu }_{\mu }$ cross-sections on water and hydrocarbon targets, and their ratios are provided by using D'Agostini unfolding method. The results of the integrated ${\bar{\nu }}_{\mu }$ cross-section measurements over this phase space are ${\sigma }_{{\mathrm{H}}_2\mathrm{O}}=(1.082\pm 0.068(stat.{)}_{-0.128}^{+0.145}(syst.))\times 10^{-39}\mathrm{c}{\mathrm{m}}^2/nucleon$, ${\sigma }_{\mathrm{CH}}=(1.096\pm 0.054(stat.{)}_{-0.117}^{+0.132}(syst.))\times 10^{-39}\mathrm{c}{\mathrm{m}}^2/nucleon$, and ${\sigma }_{{\mathrm{H}}_2\mathrm{O}}/{\sigma }_{\mathrm{CH}}=0.987\pm 0.078(stat.{)}_{-0.090}^{+0.093}(syst.)$. The ${\bar{\nu }}_{\mu }+{\nu }_{\mu }$ cross-section is ${\sigma }_{{\mathrm{H}}_2\mathrm{O}}=(1.155\pm 0.064(stat.{)}_{-0.129}^{+0.148}(syst.))\times 10^{-39}\mathrm{c}{\mathrm{m}}^2/nucleon$, ${\sigma }_{\mathrm{CH}}=(1.159\pm 0.049(stat.{)}_{-0.115}^{+0.129}(syst.))\times 10^{-39}\mathrm{c}{\mathrm{m}}^2/nucleon$, and ${\sigma }_{{\mathrm{H}}_2\mathrm{O}}/{\sigma }_{\mathrm{CH}}=0.996\pm 0.069(stat.{)}_{-0.078}^{+0.083}(syst.)$.