Benchmark on neutron capture extracted from $(d,p)$ reactions

TL;DR

This paper evaluates the use of (d,p) reactions as an indirect method to determine neutron capture cross sections relevant for nuclear astrophysics, by analyzing multiple energies and extracting key nuclear parameters.

Contribution

It introduces a benchmark analysis of (d,p) reactions at various energies to reliably extract neutron capture data for unstable nuclei.

Findings

Neutron asymptotic normalization coefficient (ANC) can be determined from low-energy (d,p) reactions.

Spectroscopic factors from 56 MeV (d,p) data are consistent with thermal (n,γ) results.

Optimal (d,p) measurement energy is around 30 MeV for similar dependence as (n,γ) reactions.

Abstract

Direct neutron capture reactions play an important role in nuclear astrophysics and applied physics. Since for most unstable short-lived nuclei it is not possible to measure the $(n, \gamma)$ cross sections, $(d,p)$ reactions have been used as an alternative indirect tool. We analyze simultaneously $^{48}{\rm Ca}(d,p)^{49}{\rm Ca}$ at deuteron energies $2, 13, 19$ and 56 MeV and the thermal $(n,\gamma)$ reaction at 25 meV. We include results for the ground state and the first excited state of $^{49}$Ca. From the low-energy $(d,p)$ reaction, the neutron asymptotic normalization coefficient (ANC) is determined. Using this ANC, we extract the spectroscopic factor (SF) from the higher energy $(d,p)$ data and the $(n, \gamma)$ data. The SF obtained through the 56 MeV $(d,p)$ data are less accurate but consistent with those from the thermal capture. We show that to have a similar dependence on the single particle parameters as in the $(n, \gamma)$, the (d,p) reaction should be measured at 30 MeV.