Summary of working group 1: theory part

Theoretical issues in Working Group 1 at Nufact’01 are summarized. Although there may not yet be complete agreement on the exact optimum baseline L and the muon energy Eμ for measurements of the CP phase at a neutrino factory, all of the studies conducted so far indicate that the optimum set (L, Eμ) tends to be smaller than (3000 km,50 GeV) if the uncertainty of the matter effect is assumed to be larger than ±5%, or the background fraction is much larger than 10−5.