arXiv 1706.017052017-06astro-ph.COhep-ph

从宇宙微波背景改进轻子不对称性的约束

Improved constraints on lepton asymmetry from the cosmic microwave background

Isabel M. Oldengott, Dominik J. Schwarz

备注：: 6 pages, 3 figures; extended discussion about the literature, accepted by EPL
DOI：: 10.1209/0295-5075/119/29001

摘要：

宇宙轻子的不对称性$η_{\text{l}}=(n_{\text{l}}-n_{\bar{\text{l}}})/n_γ$影响了原始氦的丰度和早期宇宙的膨胀率。这两种效应对宇宙微波背景（CMB）的各向异性都有影响。我们从普朗克2015年的数据中推导出中微子化学势的约束条件，假设轻子味不对称性相等，中微子质量可以忽略不计。我们发现$ξ=-0.002 ^{+0.114}_{-0.111}$（95 CL）的化学势，这对应于$ -0.085 \leq η_{\text{l}} \leq 0.084$。我们对轻子不对称性的约束明显强于以前的约束从CMB数据分析，我们认为，他们是更强大的比那些从原始轻元素丰度。由此产生的原始氦和氘丰度的限制是一致的，从直接测量。

英文摘要：

A cosmic lepton asymmetry $η_{\text{l}}=(n_{\text{l}}-n_{\bar{\text{l}}})/n_γ$ affects the primordial helium abundance and the expansion rate of the early Universe. Both of these effects have an impact on the anisotropies of the cosmic microwave background (CMB). We derive constraints on the neutrino chemical potentials from the Planck 2015 data, assuming equal lepton flavour asymmetries and negligible neutrino masses. We find $ξ=-0.002 ^{+0.114}_{-0.111}$ (95\% CL) for the chemical potentials, which corresponds to $ -0.085 \leq η_{\text{l}} \leq 0.084$. Our constraints on the lepton asymmetry are significantly stronger than previous constraints from CMB data analysis and we argue that they are more robust than those from primordial light element abundances. The resulting constraints on the primordial helium and deuterium abundances are consistent with those from direct measurements.

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