We report a measurement of the E -mode polarization power spectrum of the cosmic microwave background ( CMB ) using 150 GHz data taken from July 2014 to December 2016 with the Polarbear experiment .
We reach an effective polarization map noise level of 32 \mu \mathrm { K } - \mathrm { arcmin } across an observation area of 670 square degrees .
We measure the EE power spectrum over the angular multipole range 500 \leq \ell < 3000 , tracing the third to seventh acoustic peaks with high sensitivity .
The statistical uncertainty on E -mode bandpowers is \sim 2.3 \mu { K } ^ { 2 } at \ell \sim 1000 with a systematic uncertainty of 0.5 \mu { K } ^ { 2 } .
The data are consistent with the standard \Lambda CDM cosmological model with a probability-to-exceed of 0.38 .
We combine recent CMB E -mode measurements and make inferences about cosmological parameters in \Lambda CDM as well as in extensions to \Lambda CDM .
Adding the ground-based CMB polarization measurements to the Planck dataset reduces the uncertainty on the Hubble constant by a factor of 1.2 to H _ { 0 } = 67.20 \pm 0.57 { } ~ { } { km s ^ { -1 } Mpc ^ { -1 } } .
When allowing the number of relativistic species ( N _ { eff } ) to vary , we find N _ { eff } { } = 2.94 \pm 0.16 , which is in good agreement with the standard value of 3.046 .
Instead allowing the primordial helium abundance ( Y _ { He } ) to vary , the data favor Y _ { He } { } = 0.248 \pm 0.012 .
This is very close to the expectation of 0.2467 from Big Bang Nucleosynthesis .
When varying both Y _ { He } and N _ { eff } , we find N _ { eff } = 2.70 \pm 0.26 and Y _ { He } { } = 0.262 \pm 0.015 .