Tracking-Based Alignment of the TPOT Detector in sPHENIX at RHIC

We present a tracking-based alignment of the Time Projection Chamber Outer Tracker (TPOT), a Micromegas-based detector integrated into the sPHENIX experiment at Brookhaven National Laboratory. TPOT is positioned outside the TPC and spans a limited azimuthal coverage near mid-rapidity. It provides precise external position measurements that, when combined with hits from the inner silicon trackers, form a high-quality reference for measuring and correcting drift distortions in the Time Projection Chamber (TPC), the primary tracking detector in sPHENIX. Using data recorded without a magnetic field, we reconstruct straight-line tracks and compare them to TPOT measurements to extract alignment parameters relative to the silicon system. These corrections are validated with high-momentum helical tracks from data taken with the magnetic field on. The aligned TPOT geometry improves constraints on drift velocity and spatial distortions in the TPC. After alignment, position residuals are reduced to below 100 µm, enabling precise momentum reconstruction and enhancing the tracking performance of the full detector system.