A C++ program for estimating detector sensitivities to long-lived particles: displaced decay counter Florian Domingo, Julian Günther, Jong Soo Kim and Zeren Simon Wang Eur. Phys. J. C, 84 6 (2024) 642 Published online: 25 June 2024 DOI: 10.1140/epjc/s10052-024-13009-9