QCD improved top-quark decay at next-to-next-to-leading order Rui-Qing Meng, Sheng-Quan Wang, Ting Sun, Chao-Qin Luo, Jian-Ming Shen and Xing-Gang Wu Eur. Phys. J. C, 83 1 (2023) 59 Published online: 23 January 2023 DOI: 10.1140/epjc/s10052-023-11224-4