M. Kis

Systematic study of three-nucleon force effects in the cross section of the deuteron-proton breakup at 130 MeV

High-precision cross-section data of the deuteron-proton breakup reaction at 130 MeV are presented for 72 kinematically complete configurations. The data cover a large region of the available phase space, divided into a systematic grid of kinematical variables. They are compared with theoretical predictions, in which the full dynamics of the three-nucleon (3N) system is obtained in three different ways: realistic nucleon-nucleon (NN) potentials are combined with model 3N forces (3NFs) or with an effective 3NF resulting from explicit treatment of the Delta-isobar excitation. 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. The generated dynamics is then applied to calculate cross-section values by rigorous solution of the 3N Faddeev equations. The comparison of the calculated cross sections with the experimental data shows a clear preference for the predictions in which the 3NFs are included. The majority of the experimental data points are well reproduced by the theoretical predictions. The remaining discrepancies are investigated by inspecting cross sections integrated over certain kinematical variables. The procedure of global comparisons leads to establishing regularities in disagreements between the experimental data and the theoretically predicted values of the cross sections. They indicate deficiencies still present in the assumed models of the 3N system dynamics.

Systematic investigation of the elastic proton-deuteron differential cross section at intermediate energies

To investigate the importance of three-nucleon forces (3NF) systematically over a broad range of intermediate energies, the differential cross sections of elastic proton-deuteron scattering have been measured at proton bombarding energies of 108, 120, 135, 150, 170, and 190 MeV at c.m. angles between 30degrees and 170degrees . Comparisons with Faddeev calculations show unambiguously the shortcomings of calculations employing only two-body forces and the necessity of including 3NF. They also show the limitations of the latest few-nucleon calculations at backward angles, especially at higher beam energies. Some of these discrepancies could be partially due to relativistic effects. Data at lowest energy are also compared with a recent calculation based on chiPT .

Evidence of the Coulomb-force effects in the cross-sections of the deuteron-proton breakup at 130 MeV

High precision cross-section data of the deuteron–proton breakup reaction at 130 MeV deuteron energy are compared with the theoretical predictions obtained with a coupled-channel extension of the CD Bonn potential with virtual Δ-isobar excitation, without and with inclusion of the long-range Coulomb force. The Coulomb effect is studied on the basis of the cross-section data set, extended in this work to about 1500 data points by including breakup geometries characterized by small polar angles of the two protons. The experimental data clearly prefer predictions obtained with the Coulomb interaction included. The strongest effects are observed in regions in which the relative energy of the two protons is the smallest.

Spin-isospin selectivity in three-nucleon forces

Abstract Precision data are presented for the break-up reaction, H 2 ( p → , p p ) n , within the framework of nuclear-force studies. The experiment was carried out at KVI using a polarized-proton beam of 190 MeV impinging on a liquid-deuterium target and by exploiting the detector, BINA. Some of the vector-analyzing powers are presented and compared with state-of-the-art Faddeev calculations including three-nucleon forces effect. Significant discrepancies between the data and theoretical predictions were observed for kinematical configurations which correspond to the H 2 ( p → , He 2 ) n channel. These results are compared to the H 2 ( p → , d ) p reaction to test the isospin sensitivity of the present three-nucleon force models. The current modeling of two and three-nucleon forces is not sufficient to describe consistently polarization data for both isospin states.

Proton-deuteron radiative capture cross-sections at intermediate energies

Differential cross-sections of the reaction p(d, 3He)γ have been measured at deuteron laboratory energies of 110, 133 and 180 MeV. The data were obtained with a coincidence setup measuring both the outgoing 3He and the photon. The data are compared with modern calculations including all possible meson-exchange currents and two- and three-nucleon forces in the potential. The data clearly show a preference for one of the models, although the shape of the angular distribution cannot be reproduced by any of the presented models.

Investigation of effects beyond two-body forces in three-nucleon systems

An experiment has been performed at KVI to measure vector analyzing powers and differential cross sections of the D((p) over right arrow pd) reaction as a function of incident beam energy. The measurements have been performed so far at several kinetic energies of the incoming particle between 108 MeV and 170 MeV. In this contribution, the preliminary results for the vector analyzing power A(y) will be presented.

Cross sections of the deuteron‐proton breakup at 130 MeV

Comparison of the cross sections measured over a large part of the phase space of the deuteron‐proton breakup at 130 MeV with the results of rigorous, Faddeev‐like calculations is presented. Global analysis, including nearly 1200 data points, reveals a better agreement for theoretical predictions which include three‐nucleon force (3NF) model over the results obtained with only nucleon‐nucleon realistic potentials. A possible way to probe details of the 3NF models via studying “non‐standard” projections of the multi‐dimensional phase space is envisaged.

Analyzing power measurement in deuteron-proton breakup at 130 MeV

Vector and tensor analyzing powers of the 1H(d,pp)n breakup process have been measured at the beam energy of 130 MeV. The forthcoming results will be compared with predictions based on various 2N and 3N forces models in quest for a correct structure of the 3NF.

Proton-proton bremsstrahlung towards the elastic limit

In oder to study proton‐proton bremsstrahlung moving towards the elastic limit, a detection system, consisting of Plastic‐ball and SALAD, was set up and an experiment at 190 MeV incident beam energy was performed. Here, the experimental setup and the data analysis procedure along with some results obtained in the measurement are discussed.

Dilepton and double-photon production in proton-proton scattering at 190 MeV

The first high-statistics measurement of dilepton and double-photon yields in proton—proton scattering below the pion threshold has been performed. The data obtained allow a detailed study of off-shell effects in the proton—proton interaction.