Spectroscopy, gluon structure and polarisability of kaons in the new QCD facility at the M2 beam line at CERN SPS

The COMPASS++ /AMBER (proto-) Collaboration proposes a broad experimental programme for the “New QCD facility at the M2 beam line of the CERN SP”, to ommense after 2021. In this article, a few of unique second-generation experiments that rely on high-energy high intensity RF-separated kaon beams planned to operate after 2026 are highlighted: the kaon spectroscopy with kaon beam, a study of the gluon distribution in the kaon via prompt-photon production and a kaon polarisability measurement.