Abstract
A measurement of the analyzing powers for the ^2hbox {H}(vec {p},pp)n break-up reaction was carried out at KVI exploiting a polarized-proton beam at an energy of 135,hbox {MeV}. The scattering angles and energies of the final-state protons were measured using the Big Instrument for Nuclear-polarization Analysis (BINA) with a nearly 4pi geometrical acceptance. In this work, we analyzed a large number of kinematical geometries including forward–forward configurations in which both the final-state particles scatter to small polar angles and backward–forward configurations in which one of the final-state particles scatters to large polar angles. The results are compared with Faddeev calculations based on modern nucleon–nucleon (NN) and three-nucleon (3N) potentials. Discrepancies between polarization data and theoretical predictions are observed for configurations corresponding to small relative azimuthal angles between the two final-state protons. These configurations show a large sensitivity to 3N force effects.
Highlights
Today’s nucleon–nucleon (NN) potentials such as ArgonneV18 (AV18) [1], Reid-93 [2], Nijmegen-I and II [2] and CD-Bonn (CDB) [3,4] provide an excellent description of NN scattering observables and of the properties of the deuteron
We analyzed a large number of kinematical geometries including forward–forward configurations in which both the final-state particles scatter to small polar angles and backward–forward configurations in which one of the finalstate particles scatters to large polar angles
The experiment was performed at the Kernfysisch Versneller Instituut1 (KVI) in Groningen, the Netherlands
Summary
Today’s nucleon–nucleon (NN) potentials such as ArgonneV18 (AV18) [1], Reid-93 [2], Nijmegen-I and II [2] and CD-Bonn (CDB) [3,4] provide an excellent description of NN scattering observables and of the properties of the deuteron. Exact calculations using two-nucleon forces (2NFs) alone are not sufficient to describe, with similar accuracy, systems consisting of more than two nucleons. The 3NFs arise in the framework of meson exchange theory where a 3N interaction can be derived by means of two-pion exchange between all three nucleons with an intermediate excitation of one of them to a Δ-isobar such as in Urbana-IX (UIX) [7,8] and Tucson-Melbourne (TM99) [9,10] models or they appear fully naturally in Chiral Perturbation Theory (ChPT) at a certain order of chiral expansion [11,12,13].
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