论文标题
超出标准模型的物理：BBN和CMB的限制独立并组合
Probing Physics Beyond the Standard Model: Limits from BBN and the CMB Independently and Combined
论文作者
论文摘要
我们提出了新的大爆炸核合成（BBN）对宇宙扩张率或相对论能量密度的限制，该密度通过等效性中微子物种的数量$n_ν$量化。我们使用最新的光元观测值，中子平均寿命，并更新我们对核费率的评估$ d + d \ rightarrow he3 + n $和$ d + d + d \ rightarrow h3 + p $。将此结果与来自宇宙微波背景（CMB）的独立约束结合起来，对新物理学产生了严格的限制，这些物理学在宇宙核合成之前就会使$n_ν$和$η$结合在一起：联合BBN+CMB分析给出了$n_ν= 2.898 \ pm pm 0.141 $ n_ $ n__ $ n__ $ n__60 $ n_60 $ n_680 $ n_ pm n_141 $ n_180。我们将这些限制应用于各种各样的新物理场景，包括右撇子中微子，深色辐射和随机重力波背景。我们还搜索了$N_ν$中的潜在{\ em Change}的限制和/或两个时期之间的baryon-photon比率$η$。目前的数据对BBN和CMB解耦之间的$N_ν$的允许更改施加了强大的限制；例如，我们发现$ -0.708 <n_ν^{\ rm cmb}-n_ν^{\ rm bbn} <0.328 $，在$η$和原始氦质量分数$ y_p $之间是在两个表相之间没有变化的情况下的；我们还限制了$η$或$（η，n_ν）$的允许变化。展望未来，我们预测CMB 4阶段测量结果以及天文学\ HE4测量结果的提高精度。我们发现CMB-S4与当前的BBN结合使用，光元素观察精度可以给出$σ（n_ν）\ simeq 0.03 $。这种未来的精度将揭示中微子加热（$ n _ {\ rm eff} -3 = 0.044 $）的预期效果，在BBN期间，CMB的预期效果，并且将接近与标准模型的热平衡中的任何粒子物种。
We present new Big Bang Nucleosynthesis (BBN) limits on the cosmic expansion rate or relativistic energy density, quantified via the number $N_ν$ of equivalent neutrino species. We use the latest light element observations, neutron mean lifetime, and update our evaluation for the nuclear rates $d+d \rightarrow He3 + n$ and $d+d \rightarrow H3 + p$. Combining this result with the independent constraints from the cosmic microwave background (CMB) yields tight limits on new physics that perturbs $N_ν$ and $η$ prior to cosmic nucleosynthesis: a joint BBN+CMB analysis gives $N_ν= 2.898 \pm 0.141$, resulting in $N_ν< 3.180$ at $2σ$. We apply these limits to a wide variety of new physics scenarios including right-handed neutrinos, dark radiation, and a stochastic gravitational wave background. We also search for limits on potential {\em changes} in $N_ν$ and/or the baryon-to-photon ratio $η$ between the two epochs. The present data place strong constraints on the allowed changes in $N_ν$ between BBN and CMB decoupling; for example, we find $-0.708 < N_ν^{\rm CMB}-N_ν^{\rm BBN} < 0.328$ in the case where $η$ and the primordial helium mass fraction $Y_p$ are unchanged between the two epochs; we also give limits on the allowed variations in $η$ or in $(η,N_ν)$ jointly. Looking to the future, we forecast the tightened precision for $N_ν$ arising from both CMB Stage 4 measurements as well as improvements in astronomical \he4 measurements. We find that CMB-S4 combined with present BBN and light element observation precision can give $σ(N_ν) \simeq 0.03$. Such future precision would reveal the expected effect of neutrino heating ($N_{\rm eff}-3=0.044$) of the CMB during BBN, and would be near the level to reveal any particle species ever in thermal equilibrium with the standard model.
