# Evidence for the Cross-correlation between Cosmic Microwave Background Polarization Lensing from POLARBEAR and Cosmic Shear from Subaru Hyper Suprime-Cam

## TL;DR

This paper reports the first measurement of the cross-correlation between CMB polarization lensing from POLARBEAR and cosmic shear from Subaru HSC, providing new insights into large-scale structure and cosmology.

## Contribution

It introduces a novel cross-correlation measurement between CMB polarization lensing and galaxy shear, independent of CMB temperature data, using deep POLARBEAR and HSC observations.

## Key findings

- Reject null hypothesis at 3.5σ significance
- Measured cross-spectrum amplitude of 1.70±0.48
- Demonstrated negligible residual systematics in the analysis

## Abstract

We present the first measurement of cross-correlation between the lensing potential, reconstructed from cosmic microwave background (CMB) {\it polarization} data, and the cosmic shear field from galaxy shapes. This measurement is made using data from the POLARBEAR CMB experiment and the Subaru Hyper Suprime-Cam (HSC) survey. By analyzing an 11~deg$^2$ overlapping region, we reject the null hypothesis at 3.5$\sigma$\ and constrain the amplitude of the {\bf cross-spectrum} to $\widehat{A}_{\rm lens}=1.70\pm 0.48$, where $\widehat{A}_{\rm lens}$ is the amplitude normalized with respect to the Planck~2018{} prediction, based on the flat $\Lambda$ cold dark matter cosmology. The first measurement of this {\bf cross-spectrum} without relying on CMB temperature measurements is possible due to the deep POLARBEAR map with a noise level of ${\sim}$6\,$\mu$K-arcmin, as well as the deep HSC data with a high galaxy number density of $n_g=23\,{\rm arcmin^{-2}}$. We present a detailed study of the systematics budget to show that residual systematics in our results are negligibly small, which demonstrates the future potential of this cross-correlation technique.