Pedro da Silveira Ferreira, Stephen Owusu

We present a quadratic lensing estimator that incorporates off-diagonal correlations in both temperature and polarization CMB maps, and is capable of measuring localized lensing profiles with $<10''$ average deflection angle at the $\sim3\sigma$ level in upcoming Simons observatory (SO) data. The proposed pipeline is agnostic to the underlying mass profile and can probe the subtle signatures of voids, clusters, and topological defects. As a case study and test scenario we focus on a collapsing cosmic texture, a topological defect that has been proposed to explain the CMB Cold Spot. With the forthcoming SO data, we forecast a $2.8\sigma$ detection if the texture amplitude reaches the current Planck 2018 $2\sigma$ limit, and a $1.8\sigma$ measurement for the best-fit value, which is remarkable given the expected typical lensing angle of $<6''$. As the next-generation CMB surveys will reach $\ell>3000$ for polarization, we demonstrate that its inclusion is significant, boosting the estimator's signal-to-noise ratio by $\sim50\%$, and making it a powerful tool, allowing us to recover faint lensing footprints that were previously inaccessible.