Pion Boer–Mulders function using a contact interaction Dan-Dan Cheng, Zhu-Fang Cui, Minghui Ding, Craig D. Roberts and Sebastian M. Schmidt Eur. Phys. J. C, 85 1 (2025) 115 Published online: 30 January 2025 DOI: 10.1140/epjc/s10052-025-13782-1