Trojan Horse estimate of bare nucleus astrophysical S(E)-factor for the $\mathsf{^{6}}$Li(p,α)$^{\mathsf{3}}$He reaction and its astrophysical implications

Abstract

Abstract.The 6 Li(p, α) 3 He bare nucleus cross-section at astrophysical energies has been indirectly measured in the framework of the Trojan-Horse Method, finding an agreement within the experimental errors with the results of data extrapolations from direct methods. This result is thus an independent check of the extrapolation method used until now. The method of measure is recalled and the results are shown with particular attention to the bare cross section value at the Gamow energy. The quoted agreement between direct and indirect methods is discussed in the context of the surface lithium abundances in stars. It is shown that the problem of stellar lithium abundances is not at the nuclear physics level but it is an astrophysics problem that requires improvements in our knowledge of the mixing mechanisms, the reduction of the uncertainties on the other (nonnuclear) physical inputs, and more precise observational data.

Updated evidence of the Trojan horse particle invariance for the2H(d,p)3H reaction

“…In the last decades strong efforts were devoted to the development and application of indirect methods in nuclear astrophysics. Among the most used indirect methods, an important role is played by the Trojan Horse Method (THM) which has been applied to several reactions in the past decade [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] at the energies relevant for astrophysics (typically smaller than few hundred keV's), which usually are far below the Coulomb barrier, of the order of MeV's. Many tests have been made to fully explore the potentiality of the method and extend as much as possible its applications: the target/projectile break-up invariance [18], the spectator invariance [19,20] and the possible use of virtual neutron beams [21,22].…”

The12C(12C,α)20Ne and12C(12C,p)23Na reactions at the Gamow peak via the Trojan Horse Method

“…It has already been applied several times to reactions of relevance for astrophysics ( [26][27][28][29][30][31][32][33][34][35] and references therein). The purpose of the THM is to determine the cross section for the binary reaction (2 particles → 2 particles) A + x → C + c, from the measured cross section for the TH reaction 2 particles → 3 particles A + a → C + c + s in the quasifree (QF) kinematics regime, where the "Trojan Horse" (TH) particle, a = (x s), has a strong (s x) cluster structure.…”

AN UPDATED6Li(p, α)3He REACTION RATE AT ASTROPHYSICAL ENERGIES WITH THE TROJAN HORSE METHOD

“…In the NACRE compilation, the low-energy part of the S(E) factor is described via the extrapolation made by Kwon et al (1989). A more recent evaluation of the 6 Li(p, α) 3 He reaction rate is provided via the library JINA REACLIB (Cyburt et al 2010) which also refers to the previous TH investigation of Pizzone et al (2005). Thus, in order to upgrade the reaction rate, the low-energy trend of JINA REACLIB has been replaced here by the TH measurement (Equation (4)) in the integration of the S b (E) factor.…”

“…The evaluation of the zero energy S(E) factor was S(0) = 3.00 ± 0.19 MeV barns, while the corresponding electron screening potential was 450 ± 100 eV (details can be found in Tumino et al 2003Tumino et al , 2004. The two data sets were then included in the work of Pizzone et al (2005), where this study was devoted to calculating the TH reaction rate using the experimental fit of these two investigations and evaluating its impact during the PMS phase.…”