Cross sections and tensor analyzing powersAyyof the reactionH1(

Abstract

We measured the cross sections and tensor analyzing powers of the 1 H( d,pp)n breakup reaction at E d = 19 MeV in four symmetric constant relative energy (SCRE) configurations. The data are compared with theoretical predictions from four different approaches: the first based on high-precision (semi)phenomenological potentials alone or, the second, combined with model three-nucleon forces, and the third based on chiral forces up to next-to-next-to-leading order (NNLO) in the chiral expansion. In these cases the Coulomb interaction is not included. In addition, a fourth approach consists in a comparison with predictions based on CD Bonn including the excitation and the Coulomb force. In all cases the measured cross sections are significantly below the theoretical values, whereas the magnitudes of the tensor analyzing powers agree within the error bars in three of the four cases. The apparent discrepancies in the breakup cross sections are similar to the known differences for the space-star breakup. This adds to the data base of unsolved low-energy discrepancies (puzzles). of the nucleon-deuteron (Nd) vector analyzing power A y at energies below ≈25 MeV by all modern NN potentials [1]. In both the proton-deuteron (pd) and neutron-deuteron (nd) elastic scattering, the theoretical prediction is about 30% below the data in the angular region of the analyzing power maximum [2][3][4]. For the same reaction, but for energies above ≈60 MeV, the minima of the differential cross section are also underpredicted if only two-nucleon (2N ) forces are used [5,6]. Although this discrepancy can be removed once three-nucleon forces (3NF s) are also taken into account, the low-energy A y problem has not been resolved yet.For the breakup process the low-energy nd space-star (SST) configuration in which all three nucleons are emerging in the c.m. system with equal magnitudes of momenta in a plane perpendicular to the incoming beam direction still presents 0556-2813/2006/73(6)/064001 (12) 064001-1

Chiral three-nucleon force at N4LO: Longest-range contributions

“…Generally, one observes a good description of nucleon-deuteron elastic and breakup scattering observables at very low energies which improves when going from next-to-leading order (NLO) to N 2 LO. On the other hand, the well known puzzles in the three-nucleon continuum such as, e.g., the A y puzzle [9][10][11] and the large discrepancy for the breakup cross section in the so-called space-star and related configurations [12,13] still persist at N 2 LO. Notice, however, that the recent calculation by the Pisa group [14] demonstrates that the A y puzzle in the 4N system is significantly reduced by the chiral 3NF at N 2 LO.…”

GEANT4 simulation of dp non-mesonic breakup reaction at 300 and 500 MeV

“…The reason for these discrepancies may be the possible existence of a new type of short-range 3NFs that, for obvious reason, could not be included in the calculations. On the other hand, it has been found that in the vicinity of the Sagara discrepancy the currently known 3NFs contribute by up to 30% to the dp elastic scattering cross section at intermediate energies [9,10].…”

Current stage of studies of the star configurations at intermediate energies with the use of the BINA detector

“…The main aim is to check if the effect is still measurable for energies within this range. The only published data about the Space Star for this energy range showed lack of the effect for 65 MeV [10], while for the second highest energy (19 MeV) the effect was small, but still visible [11].…”