Cosmology from CMB lensing and delensed E E power spectra using 2019–2020 SPT-3G polarization data

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From CMB polarization data alone, we reconstruct the CMB lensing power spectrum, comparable in overall constraining power to previous temperature-based reconstructions, and an unlensed $E$-mode power spectrum, with clear detections of the third through the tenth acoustic peaks. The observations, taken in 2019 and 2020 with the South Pole Telescope (SPT) and the SPT-3G camera, cover $1500\text{ }\text{ }{\mathrm{deg}}^{2}$ at 95, 150, and 220 GHz with arcminute resolution and roughly $4.9\text{ }\text{ }\mathrm{\ensuremath{\mu}}\mathrm{K}\text{\ensuremath{-}}\mathrm{arcmin}$ coadded noise in polarization. The power spectrum estimates, together with systematic parameter estimates and a joint covariance matrix, follow from a Bayesian analysis using the marginal unbiased score expansion (MUSE) method. The $E$-mode spectrum at $\ensuremath{\ell}>2000$ and lensing spectrum at $L>350$ are the most precise to date. Assuming the $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model, and using only these SPT data and priors on $\ensuremath{\tau}$ and absolute calibration from Planck, we find ${H}_{0}=66.81\ifmmode\pm\else\textpm\fi{}0.81\text{ }\text{ }\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$, comparable in precision to the Planck determination and in $5.4\ensuremath{\sigma}$ tension with the most precise ${H}_{0}$ inference derived via the distance ladder. We also find ${S}_{8}\ensuremath{\equiv}{\ensuremath{\sigma}}_{8}({\mathrm{\ensuremath{\Omega}}}_{\mathrm{m}}/0.3{)}^{0.5}=0.850\ifmmode\pm\else\textpm\fi{}0.017$, providing further independent evidence of a slight tension with low-redshift structure probes. The $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model provides a good simultaneous fit to the combined Planck, ACT, and SPT data, and thus passes a powerful test. Combining these CMB datasets with BAO observations, we explore extensions to the $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model. We find that the effective number of neutrino species, spatial curvature, and primordial helium fraction are consistent with standard model values, and that the 95% confidence upper limit on the neutrino mass sum is 0.075 eV, close to the minimum sum expected from observations of solar and atmospheric neutrino oscillations. The SPT data are consistent with the somewhat weak ($<3\ensuremath{\sigma}$) preference for excess lensing power seen in Planck and ACT data relative to predictions of the $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model given the combined Planck, ACT, and BAO datasets. We also detect at greater than $3\ensuremath{\sigma}$ the influence of nonlinear evolution in the CMB lensing power spectrum and discuss it in the context of the ${S}_{8}$ tension. Forthcoming SPT-3G analyses will feature deeper and wider observations in temperature and polarization, providing even tighter constraints and more powerful tests of the $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model.

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