Probing hidden leptonic scalar portals using the NA64 experiment at CERNA. Ponten, H. Sieber, B. Banto Oberhauser, P. Crivelli, D. Kirpichnikov, S. N. Gninenko, M. Hösgen, L. Molina Bueno, M. Mongillo and A. ZhevlakovEur. Phys. J. C, 84 10 (2024) 1035DOI: https://doi.org/10.1140/epjc/s10052-024-13421-1