The COMPASS sandwich veto detector and a first look at kaonic final states from a $\pi^-$ (190 GeV} beam on a proton target

We introduce the sandwich veto detector that was built for the 2008 and 2009 hadron runs of the COMPASS experiment at CERN. During these beamtimes it was serving as a veto detector for neutral and charged particles outside the spectrometer acceptance, mostly thought to originate from reactions which excited the target. We also present first mass spectra from $\pi^-(190\,\GeV) p \to \pi^- \Kshort \Kshort p$ that were measured in the 2008 hadron run.