Deuteron–proton breakup at medium energies

Abstract

Recently, the database for the breakup of a deuteron in collision with a proton has been significantly enriched in the domain of medium energies. High precision experimental data for the cross section, vector (proton)-analyzing power and vector- and tensor (deuteron)-analyzing powers were collected with detection systems covering a large part of the phase space of the 1H(, pp)n and 2H(, pp)n reactions. A series of experiments were carried out with deuteron beams with energies of 100, 130 and 160 MeV and proton beams with energies of 135 and 190 MeV, each of them providing a few hundred data points per observable, obtained on systematic grids of kinematical variables within the studied angular ranges. Usage of the multidetector systems with significant solid angle coverage provides not only very rich data sets but also a good opportunity for controlling the consistency of the results. The ways of exploiting all these advantages in high precision measurements are discussed. The experimental results are compared with the theoretical predictions, in which the full dynamics of the three-nucleon (3N) system is obtained in different ways: realistic nucleon–nucleon (NN) potentials are combined with model 3N forces (3NF) or with an effective 3N interaction resulting from the explicit treatment of the Δ-isobar excitation. On top of the NN and 3N nuclear forces Coulomb interaction can be also included into the calculational framework. Relativistic calculations can be performed with realistic NN potentials alone. Alternatively, the chiral perturbation theory approach is used at the next-to-next-to-leading order with all relevant NN and 3N contributions taken into account, while at the next order without taking into account the corresponding 3NF contributions. Comparing the calculated observables with the experimental data shows the sensitivity of the cross sections to 3NFs and to Coulomb force effects, while there is no sensitivity of the deuteron vector analyzing powers to any additional dynamics beyond the NN forces. The behavior of the tensor analyzing powers and of the proton analyzing powers at higher energy is rather complicated, showing discrepancies between the calculations and the experimental data which must be considered as indications of deficiencies in the spin part of the assumed models of the 3N system dynamics. The richness of the database calls for a systematic survey of the results, therefore kinematical coordinates convenient for that purpose and certain methods of comparison to the theoretical calculations are discussed, together with signposts to future developments in the field of 3N system studies.