Test Beam Results of Planar Pixel Sensor for the CMS Phase 2 Inner Tracker Upgrade

This work presents the results of test beam measurements characterizing the performance of CMS Readout Chip (CROC) sensors for the High Luminosity Large Hadron Collider (HL-LHC) era. The HL-LHC is expected to reach a peak instantaneous luminosity of $7.5 \times 10^{34} \ \text{cm}^{-2} \ \text{s}^{-1}$, corresponding to around 200 inelastic proton-proton collisions per beam-crossing every 25 ns. To meet these challenges, the CMS tracking detector will be fully upgraded. The new tracking detector consists of an Inner Tracker closest to the beamline and an Outer Tracker surrounding it. These are populated with modules that comprise of readout chips and silicon sensors. Test beam studies of these modules are crucial for evaluating their performance. Using a 120 GeV proton beam at the Fermilab Test Beam Facility (FTBF), data was collected with a silicon tracker telescope providing precision measurements with less than 5 micron uncertainty. The beam was incident on a 1x2 planar CROC module developed by Hamamatsu, which has $100 \times 25 \ \mu\text{m}^2$ standard pixels and $225 \times 25 \ \mu\text{m}^2$ long pixels at the ROC boundary. We present characterisation of these modules that includes pixel efficiency, resolution, cluster size and charge distributions.