We perform the first blind analysis of cluster abundance data .
Specifically , we derive cosmological constraints from the abundance and weak-lensing signal of redMaPPer clusters of richness \lambda \geq 20 in the redshift range z \in [ 0.1 , 0.3 ] as measured in the Sloan Digital Sky Survey ( SDSS ) .
We simultaneously fit for cosmological parameters and the richness–mass relation of the clusters .
For a flat \Lambda CDM cosmological model with massive neutrinos , we find S _ { 8 } \equiv \sigma _ { 8 } ( \Omega _ { m } / 0.3 ) ^ { 0.5 } = 0.79 ^ { +0.05 } _ { -0.04 } .
This value is both consistent and competitive with that derived from cluster catalogues selected in different wavelengths .
Our result is also consistent with the combined probes analyses by the Dark Energy Survey ( DES ) and the Kilo-Degree Survey ( KiDS ) , and with the Cosmic Microwave Background ( CMB ) anisotropies as measured by Planck .
We demonstrate that the cosmological posteriors are robust against variation of the richness–mass relation model and to systematics associated with the calibration of the selection function .
In combination with Baryon Acoustic Oscillation ( BAO ) data and Big-Bang Nucleosynthesis ( BBN ) data \citep cookeetal16 , we constrain the Hubble rate to be h = 0.66 \pm 0.02 , independent of the CMB .
Future work aimed at improving our understanding of the scatter of the richness–mass relation has the potential to significantly improve the precision of our cosmological posteriors .
The methods described in this work were developed for use in the forthcoming analysis of cluster abundances in the DES .
Our SDSS analysis constitutes the first part of a staged-unblinding analysis of the full DES data set .