Cosmophysics Seminar ( Dr. Yuji Chinone )
POLARBEAR is a ground-based experiment designed to measure polarization of the Cosmic Microwave Background (CMB) at 150 GHz at an elevation of 5,190m in the Atacama Desert in Chile. Our main science goals are for searching for the B-mode signal created by primordial gravitational waves (PGWs) seen at degree scales, as well as for characterizing the B-mode signal from gravitational lensing with high angular resolution seen at sub-degree scales. POLARBEAR was deployed in 2011 and started science observations in 2012 focusing on small patches of the sky (deep survey). In 2014, we started to observe a large patch of the sky focusing on search for PGWs (wide survey). We have published a series of results from the deep survey, including the first/update measurement of a non-zero B-mode auto-power spectrum at sub-degree scales induced by gravitational lensing, constraint of cosmic birefringence and primordial magnetic fields, and demonstration of delensing. We also have achieved the measurement of cross-correlations of gravitational lensing between our CMB data and optical surveys by the Subaru Hyper Suprime-Cam. With the wide survey, we have reported the measurement of large angular scale B-mode signals induced by the Galactic dust foreground and successfully put an upper limit on PGWs. In this talk, I summarize the science results and achievements of the POLARBEAR experiment. I also show the status of Simons Array, which is an upgraded experiment from POLARBEAR and consists of three new receivers. Finally I describe future CMB projects which Japanese institutes have been contributing to.