Dyon in the SU(2) Yang–Mills theory with a gauge-invariant gluon mass toward quark confinement Shogo Nishino and Kei-Ichi Kondo Eur. Phys. J. C, 80 5 (2020) 454 Published online: 20 May 2020 DOI: 10.1140/epjc/s10052-020-8003-x