2016MNRAS.458.2188B

We report a new detection of neutral deuterium in the sub-Damped Lyman Alpha system with low metallicity [O/H]=-2.042±0.005 at z_abs=2.437 towards QSO J 1444+2919. The hydrogen column density in this system is logN(H i) =19.983±0.010 and the measured value of deuterium abundance is log(D/H)=-4.706±0.007_stat±0.067_syst. This system meets the set of strict selection criteria stated recently by Cooke et al. 2014 and, therefore, widens the Precision Sample of D/H. However, possible underestimation of systematic errors can bring a bias into the mean D/H value (especially if one uses a weighted mean). Hence, it might be reasonable to relax these selection criteria and thus increase the number of acceptable absorption systems with measured D/H values. The unweighted mean value of 15 robust D/H measurements gives a conservative value of the primordial deuterium abundance (D/H)_p=(2.54±0.19) x 10^–5 which is in good agreement with the prediction given by analysis of the cosmic microwave background radiation for the standard big bang nucleosynthesis. By means of the derived unweighted mean (D/H)_p value the baryon density of the Universe Ω_bh²=0.0218±0.0010 and the baryon-to-photon ratio η=(5.96±0.27) x 10^–10 have been deduced. These values have confidence intervals which are less stringent than that obtained for the Precision Sample and, thus, leave a broader window for new physics. The latter is particularly important in the light of the lithium problem.