ИСТИНА

Asymptotic normalization coefficients (ANCs) and vertex constants (VCs), which are proportional to ANCs, are important nuclear characteristics. They determine cross sections of radiative capture processes at astrophysical energies [1]. Their knowledge is necessary for solving the inverse scattering problem. 6Li nucleus in the α+d channel is one of the most interesting systems for which it is important to know VCs and ANCs. The ANC values for this system determine the cross section of the radiative capture 4He(d,γ) 6Li, which is the only process of 6Li formation in the Big Bang model. The available data on the values of the ANCs Cl for the 6Li→ α+d channel (l=0, 2) are characterized by a large spread [2, 3]. In the first place it refers to the D state constants. In the given work, the Cl and Gl values for the 6Li→ α+d channel are found by analytic continuation in energy of the effective range expansion for the dα scattering to the pole corresponding to the bound 6Li state. Lately suggested two-channel version of the effective range expansion [4] is employed. Several sets of scattering phases are used as an input. 1. The phase-shift analysis made in [5] with neglect of the coupling of l=0 and l=2 channels (set 1). 2. The phase-shift analysis made in [6] with account of the channel coupling (set 2). 3. Faddeev calculations in the 3-body model (n, p, α) neglecting the Coulomb interaction [2] (set 3). The calculations are performed with and without the preassigned (fixed) value of the 6Li binding energy ε. Set 1 and set 2 taken together result in G02 = 0.4 – 0.5 fm, C0 = 2.3 – 2.8 fm-1/2. Set 3 leads to G02 = 0.3 fm, C0 = 2.0 fm-1/2. Low accuracy of phase-shift analyses at low energies and simplicity of Faddeev equations used did not let to obtain accurate values of the VC and ANC for l = 2. The result is: C2 = 0.02 – 0.05 fm-1/2. The sign of C2 (relative to C0) turned out to be positive. It follows from the numerical results obtained that the absolute values of Cl and Gl increase with increasing ε as well as with taking account of the Coulomb interaction. Account of the channel coupling affects only slightly the C0 and G0 values. On the other hand, account of that coupling is absolutely necessary to get the reliable C2 and G2 values. It may be concluded that the method suggested is operable. To get the more accurate values of VCs and ANCs for 6Li→α + d it is desirable: • To measure more accurately the dα scattering differential cross section at low energies • To perform the thorough phase-shift analysis of the corresponding data • To perform Faddeev calculations of 6Li in the 3-body model with realistic pair potentials and account of the Coulomb interaction. References 1. A.M. Mukhamedzhanov and R.E. Tribble, Phys. Rev. C52, 3418 (1999). 2. L.D.Blokhintsev, V.I.Kukulin, A.A.Sakharuk, D.A.Savin, E.V.Kuznetsova. Phys. Rev. C48, 2390 (1993). 3. L.D.Blokhintsev, S.B.Igamov, M.M.Nishonov, R.Yarmukhamedov. Phys. At. Nucl., 2006. V.69. P.433. 4. L.D.Blokhintsev . Phys. At. Nucl., 2011, V.74. P.979; Bull. Russ. Acad. Sci. Physics, 2012. V.76. P.425. 5. V.M.Krasnopol’sky et al., Phys. Rev.C43, 822 (1991) . 6. W.Grϋebler et al., Nucl. Phys. A242, 265 (1975); Nucl. Phys. A397, 61 (1983).