Precision measurement of the structure of the CMS inner tracking system using nuclear interactions with data collected in 2018

The structure of the CMS inner tracking system has been studied using nuclear interactions of hadrons striking its material. Data from proton-proton collisions at a center-of-mass energy of 13 TeV recorded in 2018 at the LHC are used to reconstruct millions of secondary vertices from these nuclear interactions. Precise positions of the beam pipe and the inner tracking system elements, such as the pixel detector support tube and support rails, are determined using these vertices. These measurements are important for detector simulations, detector upgrades, and to identify any changes in the positions of inactive elements. Results of 2018 data with the upgraded (Phase-1) pixel detector, which was installed in Spring 2017, have been compared with published 2015 data (original pixel detector.)