A construction of slice knots via annulus twists

We give a new construction of slice knots via annulus twists. The simplest slice knots obtained by our method are those constructed by Omae. In this paper, we introduce a sufficient condition for given slice knots to be ribbon, and prove that all Omae's knots are ribbon.
Comment: 26 pages and 28 figures. Comments are welcome.Version 2: A new section added. Version 3: The definition of an annulus twist was clarified. The anonymous referee pointed out a gap of Theorem 3.1. The statement of Theorem 3.1 was weakened. Version 4: Abstract, Introduction and Section 6 are rewritten