Constraining light sterile neutrino mass with the BICEP2/Keck array 2014 B-mode polarization data

Abstract

Abstract We explore the thermal light sterile neutrino situation from cosmological perspective in the $$\Lambda \text {CDM} + r_{0.05} + N_{\text {eff}} + m^{\text {eff}}_{\text {s}}$$ ΛCDM+r0.05+Neff+mseff model using combinations of latest data sets available. Among CMB datasets, we use Planck 2015 temperature and low-l polarization data and the latest data release on the B-mode polarization from the BICEP2/Keck collaboration (BK14). We also use the latest Baryon Acoustic Oscillations (BAO) data from SDSS-III BOSS DR12, MGS, and 6dFS; and a Gaussian prior (HST) on the Hubble constant ($$H_0 = 73.24 \pm 1.74$$ H0=73.24±1.74 km/s/Mpc) from direct measurements by Hubble Space Telescope. We find that inclusion of BK14 data makes the constraints on the effective mass of sterile neutrino ($$m^{\text {eff}}_{\text {s}}$$ mseff ) slightly stronger by preferring higher $$\sigma _8$$ σ8 values. The bound of $$m^{\text {eff}}_{\text {s}}<$$ mseff< 0.46 eV (95% C.L.) is found for the combination of Planck 2015, BAO and BK14 datasets, whereas the bound is $$m^{\text {eff}}_{\text {s}}<$$ mseff< 0.53 eV (95% C.L.) without the BK14 data. Our most aggressive bound of $$m^{\text {eff}}_{\text {s}}<$$ mseff< 0.28 eV (95% C.L.) is obtained with Planck 2015, HST and BK14. Our analysis indicates that fully thermalized sterile neutrinos with mass $$\sim 1$$ ∼1 eV are slightly more disfavoured with the inclusion of BK14 data. It also seems to make the agreement between Planck 2015 and CFHTLenS (weak gravitational lensing data) worse due to the higher $$\sigma _8$$ σ8 values.