Tertiary collimator closure test in physics

An end-of-ll MD was carried out on October 18 2016, where a standard physics ll was taken over close to the end. The vertical TCTs in front of the high-luminosity experiments ATLAS and CMS were then closed by about 0.5 , in order to investigate if this would cause any increase in experimental background. The TCTs were left in the closer position for around 1.5 h, and then moved out again to the standard setting. A rst analysis shows no eect on the background in any of the experiments, which provides valuable inputs to the choice of operational TCT setting in the future and for the understanding of the importance of dierent background sources.