Singlet fermionic dark matter with dark Z Dong-Won Jung, Soo-hyeon Nam, Chaehyun Yu, Yeong Gyun Kim and Kang Young Lee Eur. Phys. J. C, 80 6 (2020) 513 Published online: 08 June 2020 DOI: 10.1140/epjc/s10052-020-8080-x