  Measurements of particle emission from a replica of the T2K 90 cm-long carbon
target were performed in the NA61/SHINE experiment at CERN SPS, using data
collected during a high-statistics run in 2009. An efficient use of the
long-target measurements for neutrino flux predictions in T2K requires
dedicated reconstruction and analysis techniques. Fully-corrected differential
yields of $\pi^\pm$-mesons from the surface of the T2K replica target for
incoming 31 GeV/c protons are presented. A possible strategy to implement these
results into the T2K neutrino beam predictions is discussed and the propagation
of the uncertainties of these results to the final neutrino flux is performed.
