R1-Reward: Training Multimodal Reward Model Through Stable Reinforcement Learning - Zhang, YiFan; Lu, Xingyu; Hu, Xiao; Fu, Chaoyou; Wen, Bin; Zhang, Tianke; Liu, Changyi; Jiang, Kaiyu; Chen, Kaibing; Tang, Kaiyu; Ding, Haojie; Chen, Jiankang; et al. (International Conference on Learning Representations, 2026)