Marcucci L E, Mangano G, Kievsky A, Viviani M
Department of Physics, University of Pisa, Largo B. Pontecorvo 3, I-56127 Pisa, Italy.
INFN-Pisa, Largo B. Pontecorvo 3, I-56127 Pisa, I-56127 Pisa, Italy.
Phys Rev Lett. 2016 Mar 11;116(10):102501. doi: 10.1103/PhysRevLett.116.102501. Epub 2016 Mar 8.
The astrophysical S factor for the radiative capture d(p,γ)^{3}He in the energy range of interest for big bang nucleosynthesis (BBN) is calculated using an ab initio approach. The nuclear Hamiltonian retains both two- and three-nucleon interactions-the Argonne v_{18} and the Urbana IX, respectively. Both one- and many-body contributions to the nuclear current operator are included. The former retain for the first time, besides the 1/m leading order contribution (m is the nucleon mass), also the next-to-leading order term, proportional to 1/m^{3}. The many-body currents are constructed in order to satisfy the current conservation relation with the adopted Hamiltonian model. The hyperspherical harmonics technique is applied to solve the A=3 bound and scattering states. Particular attention is paid in this second case in order to obtain, in the energy range of BBN, an uncertainty on the astrophysical S factor of the order or below ∼1%. Then, in this energy range, the S factor is found to be ∼10% larger than the currently adopted values. Part of this increase (1%-3%) is due to the 1/m^{3} one-body operator, while the remaining is due to the new more accurate scattering wave functions. We have studied the implication of this new determination for the d(p,γ)^{3}He S factor on the deuterium primordial abundance. We find that the predicted theoretical value for ^{2}H/H is in excellent agreement with its experimental determination, using the most recent determination of the baryon density of the Planck experiment, and with a standard number of relativistic degrees of freedom N_{eff}=3.046 during primordial nucleosynthesis. This calls for a more accurate measurement of the astrophysical S factor in order to confirm the present predictions.
利用从头算方法计算了在大爆炸核合成（BBN）感兴趣的能量范围内，辐射俘获d(p,γ)^{3}He的天体物理S因子。核哈密顿量同时保留了两体和三体相互作用，分别为阿贡v_{18}和厄巴纳IX。核流算符的单体和多体贡献均被包含在内。前者除了首次保留1/m主导阶贡献（m为核子质量）外，还保留了与1/m^{3}成正比的次主导阶项。构建多体流是为了满足与所采用的哈密顿量模型的流守恒关系。超球谐函数技术被应用于求解A = 3的束缚态和散射态。在第二种情况下给予了特别关注，以便在BBN的能量范围内获得天体物理S因子约1%或更低的不确定性。然后，在这个能量范围内，发现S因子比目前采用的值大约10%。这种增加的一部分（1%-3%）归因于1/m^{3}单体算符，而其余部分归因于新的更精确的散射波函数。我们研究了d(p,γ)^{3}He S因子这一新测定对氘原始丰度的影响。我们发现，使用普朗克实验对重子密度的最新测定，以及原初核合成期间相对论自由度的标准数量N_{eff}=3.046，^{^{2}H/H}的预测理论值与其实验测定结果非常吻合。这需要对天体物理S因子进行更精确的测量，以确认当前的预测。
