The analysis described here is not an official result of the T2K experiment. However, it was further developed and has since been published:
Neutrino-induced coherent pion production is an important channel for the study of neutrino-nucleus interactions. It is both a dangerous background for νe oscillation experiments, and a critical component required for precise understanding of neutrino-nucleus pion production in general.
The body of experimental evidence for coherent pion production at high neutrino energies is reviewed. This data is described well by the Rein-Sehgal model, which is described and studied. In light of recent low energy limits set below the Rein-Sehgal model cross-section an alternative low energy model, the Alvarez-Ruso model, was implemented in the neutrino interaction simulation GENIE. The results of this simulation are compared with those from the Rein-Sehgal model, and briefly with those from other models.
Finally, a search for νμ-induced charged-current (CC) coherent pion production on 12C was conducted at a mean neutrino energy of 0.86 GeV, using data from the T2K experiment's off-axis near detector. A 3.0 σ excess of events was found above the background prediction, constituting the first experimental evidence of CC coherent pion production below 7 GeV. Preliminary attempts to interpret this excess in the context of the Rein-Sehgal and Alvarez-Ruso models found cross-sections consistent with the limits set by SciBooNE.