Optical appearance and shadow of Kalb–Ramond black hole: effects of plasma and accretion models Mou Xu, Ruonan Li, Jianbo Lu, Shining Yang and Shu-Min Wu Eur. Phys. J. C, 85 6 (2025) 676 Published online: 20 June 2025 DOI: 10.1140/epjc/s10052-025-14418-0