Few-body problems in nuclear astrophysics

Abstract

Abstract. Few-body methods provide very useful tools to solve different problems important for nuclear astrophysics. Some of them are discussed below. TRIPLE COLLISIONSBinary collisions are dominant in stellar environments. But since nuclear reactions occur in a stellar plasma, it is important to estimate the impact of the medium on the elementary processes. The dynamic effect of the medium is to produce triple nonradiative collisions. To calculate the reaction rates for such processes, we use a genuine threebody Coulomb scattering wave function, which is exact in the asymptotic region where two particles are close to each other and far away from the third (spectator) particle. We have estimated reaction rates of 7 Be´ep eµ 8 B and 7 Be´pp pµ 8 B triple collisions leading to the nonradiative formation of 8 B. For solar core conditions we find that the triple collision rates for 7 Be´ep eµ 8 B and 7 Be´pp pµ 8 B are approximately 10 5 and 10 12 of that for the binary one 7 Be´p γµ 8 B. Triple collisions play a minor role in stellar matter unless temperatures and densities are high. COULOMB BREAKUPIt is very difficult, or often impossible, to measure under lab conditions nuclear cross sections at stellar energies. That is why different indirect techniques, such as Coulomb breakup reactions, are useful for getting at the desired astrophysical information. This information can be distorted by the final-state three-body Coulomb interaction (postdecay Coulomb acceleration). A correct treatment of the final-state rescattering requires the use of a genuine scattering wave function for three charged particles in the contin-

Relation between Proton and Neutron Asymptotic Normalization Coefficients for Light Mirror Nuclei and its Relevance to Nuclear Astrophysics

“…It follows from [4,5,7] that C lj can be expressed in terms of the many-body wave functions of the nuclei A and B:…”

“…The incorrect behavior of these model wave functions at large distances plays a minor role because of the presence of the short range NN potential on the right hand side in Eq. (2) [7]. We have performed such calculations for several 0p nuclei, some of which are of astrophysical importance, with a range of NN potentials using fixed 0hω wave functions obtained in [8], [29].…”

Reexamination of the astrophysicalSfactor for theα+d→6Li

“…The ANC plays a very important role in nuclear astrophysics because many astrophysical radiative capture processes are peripheral and their overall normalization is governed by the tail of the overlap function, i.e. by the ANC [15][16][17][18]. Among the important astrophysical processes, where the ANC plays a crucial role, is the primordial radiative capture process α + d → 6 Li + γ, which is the only process that produces 6 Li in the big bang model.…”

Coulomb breakup of6Li intoα+din the field of a208Pb ion

“…Additionally, we note that for the energy E αd > 3 MeV the reaction is no longer peripheral. We have not calculated the cross section above 6 MeV because the phase shifts have a large imaginary part due to the open α + p + n, 5 He + p and 5 Li + n channels from the energy E > 5 MeV and the restriction by the single αd channel becomes incorrect. From Fig.…”

“…Among these indirect methods we cite the elastic Coulomb dissociation method suggested by Baur, Bertulani and Rebel [1][2][3], the asymptotic normalization coefficient method (ANC) suggested by Mukhamedzhanov and Timofeyuk [4][5][6], and the Trojan horse method (THM) suggested by Baur and modified by Spitaleri [7,8]. The study of nuclear reactions at high energy is, in general, very complicated owing to the strong nuclear interaction between the colliding nuclei.…”