Comprehensive investigation of the symmetric space-star configuration in the nucleon-deuteron breakup

Abstract

We examine a description of available cross section data for symmetric space star (SST) configurations in the neutron-deuteron (nd) and proton-deuteron (pd) breakup reaction using numerically exact solutions of the three-nucleon (3N) Faddeev equation based on two-and three-nucleon (semi)phenomenological and chiral forces. The predicted SST cross sections are very stable with respect to the underlying dynamics for incoming nucleon laboratory energies below ≈ 25 MeV. We discuss possible origins of the surprising discrepancies between theory and data found in low-energy nd and pd SST breakup measurements.

Measurement of the α-particle monopole transition form factor challenges theory: a low-energy puzzle for nuclear forces?

“…Interestingly, another recent investigation [32] shows that the 0 + 2 state in 4 He is very sensitive to the particular parameterization of the chiral 3N force. This puzzle may resemble otherstill unresolved-low-energy puzzles, such as the so called A y [33][34][35][36] and SST [37] puzzles, where the most sophisticated nuclear forces are not able to explain experimental observations in the few-body sector.…”