Effects of the detector non-uniformity in pion directed flow measurement relative to the spectator plane by the NA49 experiment at the CERN SPSOleg Golosov, Evgeny Kashirin, Viktor Klochkov and Ilya SelyuzhenkovEPJ Web Conf., 204 (2019) 06011DOI: https://doi.org/10.1051/epjconf/201920406011