Measurements of the $\hat{I}{½}_{\hat{I}}¼$ and $\bar{\hat{I}}{½}_{\hat{I}}¼$-induced Coherent Charged Pion Production Cross Sections on ${}^{12}C$ by the T2K experiment

Abstract

We report an updated measurement of the $\hat{I}{½}_{\hat{I}}¼$-induced, and the first measurement of the $\bar{\hat{I}}{½}_{\hat{I}}¼$-induced coherent charged pion production cross section on ${}^{12}C$ nuclei in the T2K experiment. This is measured in a restricted region of the final-state phase space for which $p_{\hat{I}¼,\ddot{I}€}>0.2$ GeV, $\cos (\hat{I}{¸}_{\hat{I}}¼)>0.8$ and $\cos (\hat{I}{¸}_{\ddot{I}}€)>0.6$, and at a mean (anti)neutrino energy of 0.85 GeV using the T2K near detector. The measured $\hat{I}{½}_{\hat{I}}¼$ CC coherent pion production flux-averaged cross section on ${}^{12}C$ is $(2.98\pm 0.37(stat.)\pm 0.31(syst.)\begin{array}{c}+0.49\\ -0.00\end{array}({\mathrm{Q}}^2\mathrm{model}))\times 10^{-40}{\mathrm{cm}}^2$. The new measurement of the $\bar{\hat{I}}{½}_{\hat{I}}¼$-induced cross section on ${}^{12}C$ is $(3.05\pm 0.71(stat.)\pm 0.39(syst.)\begin{array}{c}+0.74\\ -0.00\end{array}({\mathrm{Q}}^2\mathrm{model}))\times 10^{-40}{\mathrm{cm}}^2$. The results are compatible with both the NEUT 5.4.0 Berger-Sehgal (2009) and GENIE 2.8.0 Rein-Sehgal (2007) model predictions.