ISR effects on loop corrections of a top pair-production at the ILC

Precise predictions for an e ⁺ e ^- → tt¯ cross section are presented at an energy region from 400 GeV to 800 GeV. Cross sections are estimated including the beam-polarization effects with full { O}(α ), and also with effects of the initial-state photon emission. A resummation technique is used for the initial-state photon emission up to two-loop order. A pure-weak correction is defined as the full electroweak corrections without the initial-state photonic corrections. As a result, it is obtained that the total cross section of a top quark pair-production receives the pure-weak corrections of +4% over the trivial initial state corrections at a center of mass energy of 500 GeV. Among the initial state contributions, a contribution from two-loop diagrams gives -5% correction over the one-loop ones at the center of mass energy of 500 GeV.