用Planck和BICEP2探测核速率
Probing nuclear rates with Planck and BICEP2
摘要：
大爆炸核合成（BBN）将关键的宇宙学参数与轻元素的原始丰度联系起来。在本文中，我们指出，最近的观测宇宙微波背景各向异性的普朗克卫星和BICEP 2实验约束这些参数具有如此高的精度水平，原始氘丰度可以推断出显着的精度。对于一个给定的宇宙学模型，我们可以获得与BBN相关的能量范围内的核过程的独立信息，这些信息决定了最终的^2H/H产额。特别是，在假设标准宇宙学模型的情况下，我们证明了对普朗克数据和最近在贫金属阻尼莱曼-α系统中氘丰度测量结果的综合分析提供了关于辐射俘获反应d（p，γ）^3 He将氘转化为氦的截面的独立信息。有趣的是，结果是高于目前的实验数据在BBN能量范围（10 - 300千电子伏）的拟合建议的值，而它是在更好的协议与从头计算理论计算，基于模型的核电磁流来自现实的相互作用。由于上述核过程的速率与中微子的有效数Neff之间的相关性，同样的分析也指出Neff>3。我们展示了当假设一个非最小的宇宙学场景时，这种观察是如何变化的。我们的结论是，在几百keV范围内，可以通过像LUNA这样的实验收集到更多的d（p，γ）^3 He截面数据，这些数据要么可以证实这个速率值很低，要么可以提供一些有利于接近最小宇宙学情景的线索。
英文摘要：
Big Bang Nucleosynthesis (BBN) relates key cosmological parameters to the primordial abundance of light elements. In this paper, we point out that the recent observations of Cosmic Microwave Background anisotropies by the Planck satellite and by the BICEP2 experiment constrain these parameters with such a high level of accuracy that the primordial deuterium abundance can be inferred with remarkable precision. For a given cosmological model, one can obtain independent information on nuclear processes in the energy range relevant for BBN, which determine the eventual ^2H/H yield. In particular, assuming the standard cosmological model, we show that a combined analysis of Planck data and of recent deuterium abundance measurements in metal-poor damped Lyman-alpha systems provides independent information on the cross section of the radiative capture reaction d(p,γ)^3He converting deuterium into helium. Interestingly, the result is higher than the values suggested by a fit of present experimental data in the BBN energy range (10 - 300 keV), whereas it is in better agreement with ab initio theoretical calculations, based on models for the nuclear electromagnetic current derived from realistic interactions. Due to the correlation between the rate of the above nuclear process and the effective number of neutrinos Neff, the same analysis points out a Neff>3 as well. We show how this observation changes when assuming a non-minimal cosmological scenario. We conclude that further data on the d(p,γ)^3He cross section in the few hundred keV range, that can be collected by experiments like LUNA, may either confirm the low value of this rate, or rather give some hint in favour of next-to-minimal cosmological scenarios.
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