Doping evolution of the quasiparticle excitations in heavily hole-doped Ba 1 - X K x Fe 2 As 2: A possible superconducting gap with sign-reversal between hole pockets

D. Watanabe, T. Yamashita, Y. Kawamoto, S. Kurata, Y. Mizukami, T. Ohta, S. Kasahara, M. Yamashita, T. Saito, H. Fukazawa, Y. Kohori, S. Ishida, K. Kihou, C. H. Lee, A. Iyo, H. Eisaki, A. B. Vorontsov, T. Shibauchi, Y. Matsuda