# Cross-correlating the patchy screening and kinetic Sunyaev-Zel'dovich effects as a new probe of reionization

**Authors:** Darby Kramer, Alexander van Engelen, Christopher Cain, Niall MacCrann, Hy Trac, Skylar Grayson, Evan Scannapieco, Blake Sherwin  
**arXiv:** [2501.07623](https://arxiv.org/abs/2501.07623)  
**Date:** 2025-01-13  
**Summary page:** https://www.summarizepaper.com/en/paper/2501.07623v1/

## Abstract

The kinetic Sunyaev-Zel'dovich effect (kSZ) and patchy screening effect are two complementary cosmic microwave background (CMB) probes of the reionization era. The kSZ effect is a relatively strong signal, but is difficult to disentangle from other sources of temperature anisotropy, whereas patchy screening is weaker but can be reconstructed using the cleaner polarization channel. Here, we explore the potential of using upcoming CMB surveys to correlate a reconstructed map of patchy screening with (the square of) the kSZ map, and what a detection of this cross-correlation would mean for reionization science. To do this, we use simulations and theory to quantify the contributions to this signal from different redshifts. We then use the expected survey properties for CMB-S4 and CMB-HD to make detection forecasts before exploring how the signal depends on reionization parameters. We forecast that CMB-S4 will obtain a hint of this signal at up to 1.8$\sigma$ and CMB-HD will detect it at up to 14$\sigma$. We find that this signal contains unique information about the timing and morphology of reionization, particularly sensitivity to the first half of reionization and to the bispectrum of the ionized gas distribution.