Internal delensing of cosmic microwave background polarization B-modes with the POLARBEAR experiment

Using only cosmic microwave background polarization data from the POLARBEAR experiment, we measure B-mode polarization delensing on subdegree scales at more than 5s significance. We achieve a 14% B-mode power variance reduction, the highest to date for internal delensing, and improve this result to 22% by applying for the first time an iterative maximum a posteriori delensing method. Our analysis demonstrates the capability of internal delensing as a means of improving constraints on inflationary models, paving the way for the optimal analysis of next-generation primordial B-mode experiments.