Institution(s): 1. Institut d'Astrophysique Spatiale (IAS), LAL et CNRS
One of the main challenge left for the present and the future CMB experiments is the high precision measurement of the CMB polarization at large angular scales. The reionization bump in the CMB polarization EE and BB power spectra encodes unique informations about the reionization history of the Universe and the inflationary epoch. Such valuable information can be accessed only with an unprecedented accuracy and care on each step of the data analysis and its interpretation. The Planck 2014 release represents a first step towards the accurate characterization of the CMB polarization on the full sky. In this talk I will go through a brief introduction about the CMB polarization mainly focusing on the large angular scales. I will show how the EE and BB spectra at low-l can be used to improve the constraints on the cosmological parameters, in particular those related to the reionization history (τ) and the amount of tensor modes (r). As a Planck Scientist I will present, on behalf of the Planck collaboration, the status of the CMB analysis at large scales after the 2014 release. I will present different methods that can be used for the low-l analysis, focusing on a spectral based approach (Mangilli et al. in preparation). Finally I will present the theoretical implications of the results and the future prospects in view of the Planck release at the end of 2015 and future CMB experiments.