Eur. Phys. J. A (2006) 27: 205-215
https://doi.org/10.1140/epja/i2006-08-032-7

Nuclear Physics in Astrophysics II

Indirect techniques in nuclear astrophysics

Asymptotic Normalization Coefficient and Trojan Horse

¹ Cyclotron Institute, Texas A&M University, College Station, 77843, TX, USA
² Institute of Nuclear Physics, Moscow State University, Moscow, Russia
³ N.S.C.L. and Department of Physics and Astronomy, Michigan State University, East Lansing, MI, USA
⁴ Nuclear Physics Institute of Czech Academy of Sciences, Prague-Řež, Czech Republic
⁵ Laboratori Nazionali del Sud, DMFCI, Università di Catania, Catania, Italy and INFN, Catania, Italy
⁶ Physics Department, National University, Tashkent, Uzbekistan
⁷ Physics Division, Argonne National Laboratory, 60439, Argonne, IL, USA

Received: 21 June 2005
Accepted: 20 December 2005
Published online: 15 March 2006

Abstract

Owing to the presence of the Coulomb barrier at astrophysically relevant kinetic energies it is very difficult, or sometimes impossible, to measure astrophysical reaction rates in the laboratory. That is why different indirect techniques are being used along with direct measurements. Here we address two important indirect techniques, the asymptotic normalization coefficient (ANC) and the Trojan Horse (TH) methods. We discuss the application of the ANC technique for calculation of the astrophysical processes in the presence of subthreshold bound states, in particular, two different mechanisms are discussed: direct capture to the subthreshold state and capture to the low-lying bound states through the subthreshold state, which plays the role of the subthreshold resonance. The ANC technique can also be used to determine the interference sign of the resonant and nonresonant (direct) terms of the reaction amplitude. The TH method is unique indirect technique allowing one to measure astrophysical rearrangement reactions down to astrophysically relevant energies. We explain why there is no Coulomb barrier in the sub-process amplitudes extracted from the TH reaction. The expressions for the TH amplitude for direct and resonant cases are presented.