Figure 28

Left: Cosmic-ray tracks with at least 100 TPC clusters and 5 TRD layers, recorded without magnetic field, used for the relative $r\varphi$ alignment of the TRD chambers within stacks (internal alignment). Right: Charged-particle tracks with at least 100 TPC clusters and 4 TRD layers from \pp collisions at $\sqrts=8$ TeV, used for the alignment of the TRD with respect to the TPC (external alignment). Both figures show data from 2012 (setup with 13 supermodules).