α+d→Li6+γ astrophysical S factor and its implications for Big Bang nucleosynthesis

Abstract

The α + d → 6 Li + γ radiative capture is studied in order to predict the 6 Li primordial abundance. Within a two-body framework, the α particle and the deuteron are considered the structureless constituents of 6 Li. Five α + d potentials are used to solve the two-body problem: four of them are taken from the literature, only one having also a tensor component. A fifth model is here constructed in order to reproduce, besides the 6 Li static properties as binding energy, magnetic dipole, and electric quadrupole moments, also the S-state asymptotic normalization coefficient (ANC). The two-body bound and scattering problem is solved with different techniques, in order to minimize the numerical uncertainty of the present results. The long-wavelength approximation is used, and therefore only the electric dipole and quadrupole operators are retained. The astrophysical S factor is found to be significantly sensitive to the ANC, but in all the cases in good agreement with the available experimental data. The theoretical uncertainty has been estimated of the order of few percent when the potentials which reproduce the ANC are considered, but increases up to 20% when all five potential models are retained. The effect of this S-factor prediction on the 6 Li primordial abundance is studied, using the public code PArthENoPE. For the five models considered here we find 6 Li/H = (0.9-1.8) × 10 −14 , with the baryon density parameter in the 3-σ range of Planck 2015 analysis, b h 2 = 0.022 26 ± 0.000 23.

Neutron halos in the excited states of B12

“…Application of the ANC theory [19][20][21][22][23] to peripheral reactions on light nuclei is especially adequate for determining the radii of halos [17,24]. In actual practice, the ANC theory is widely used to obtain spectroscopic and astrophysical information [25][26][27][28][29].…”

The α+d→Unknown node mmultiscripts found in MathML fragment.i+γ$\alpha + d \to {}^{6}{\rm{Li}} + \gamma $ reaction and the second Lithium puzzle

“…The total astrophysical S -factor, as calculated in Ref. [2], in the energy range 10 keV-1.5 MeV. The experimental data have been taken from Ref.…”

“…In Ref. [2] a new potential terms has been added in order to reproduce all the scattering phase shifts up to total angular momentum J = 3 and orbital angular momentum = 2. The two new potentials containing a tensor term are therefore…”

“…• a modified version of V T , which additionally reproduces the 6 Li ANC, first published in Ref. [2]…”

Low-energy bound states, resonances, and scattering of light ions

“…Theoretical approaches can roughly be divided into two kinds, taking either the ions as degrees of freedom or starting from individual nucleons. The former approach includes a variety of models [2][3][4][5], effective range expansions [6][7][8][9][10][11][12], and effective field theories (EFTs) [13][14][15][16][17][18]; the microscopic approach ranges from simpler models [19] to ab initio computations [20][21][22][23]. Unfortunately, there are still significant uncertainties [1], and data tables for relevant quantities such as asymptotic normalization coefficients (ANCs) or astrophysical S factors may [24] or may not [25,26] contain theoretical uncertainties.…”