Nucleons In Deuteron Research Articles

Exploring Three Nucleon Forces with Nucleon–Deuteron Scattering

Recent progress on three nucleon force study with three nucleon scattering at intermediate energies ( E / A ≈ 100 MeV ) is presented, especially focusing on the experimental work on deuteron–proton elastic scattering and breakup reactions at RIKEN. The first signature of three nucleon forces is identified in the cross section minimum for deuteron–proton elastic scattering by direct comparison between the precise data and state of the art Faddeev calculations based on the nucleon–nucleon forces plus the 2 π–exchange three nucleon forces. However the polarization observables are not always properly described by adding the three nucleon forces, indicating that components other than 2 π–exchange three nucleon forces are required to describe the data.

Centrality dependence of charged hadron production in deuteron+gold and nucleon+gold collisions atsNN=200GeV

We present transverse momentum (p(T)) spectra of charged hadrons measured in deuteron-gold and nucleon-gold collisions at root s(NN)=200 GeV for four centrality classes. Nucleon-gold collisions were selected by tagging events in which a spectator nucleon was observed in one of two forward rapidity detectors. The spectra and yields were investigated as a function of the number of binary nucleon-nucleon collisions, nu, suffered by deuteron nucleons. A comparison of charged particle yields to those in p+p collisions show that yield per nucleon-nucleon collision saturates with nu for high momentum particles. We also present the charged hadron to neutral pion ratios as a function of p(T).

Forward Λ production and nuclear stopping power ind+Aucollisions atsNN=200GeV

We report the measurement of {lambda} and {lambda} yields and inverse slope parameters in d+Au collisions at {radical}(s{sub NN})=200 GeV at forward and backward rapidities (y={+-}2.75), using data from the STAR forward time projection chambers. The contributions of different processes to baryon transport and particle production are probed exploiting the inherent asymmetry of the d+Au system. Comparisons to model calculations show that baryon transport on the deuteron side is consistent with multiple collisions of the deuteron nucleons with gold participants. On the gold side, HIJING-based models without a hadronic rescattering phase do not describe the measured particle yields, while models that include target remnants or hadronic rescattering do. The multichain model can provide a good description of the net baryon density in d+Au collisions at energies currently available at the BNL Relativistic Heavy Ion Collider, and the derived parameters of the model agree with those from nuclear collisions at lower energies.

Λ production at forward and backward rapidity in d+Au collisions at

Using the forward time projection chambers of the STAR experiment at the Brookhaven Relativistic Heavy-Ion Collider, we measure the centrality-dependent Λ and yields and the inverse slope parameters in d+Au collisions at forward and backward rapidities y = ±2.75. The contributions of different processes to stopping and baryon transport are probed exploiting the inherent asymmetry of the d+Au system. Comparisons to model calculations show that the baryon transport on the deuteron side is due to multiple collisions of the deuteron nucleons with gold participants. On the gold side, the inclusion of initial-state nuclear effects or hadronic rescattering is necessary to describe the data.

Three- and Four-Body Correlations in Nuclear Matter

Few-nucleon correlations in nuclear matter at finite densities and temperatures are explored. Using the Dyson equation approach leads to effective few-body equations that include self energy corrections and Pauli blocking factors in a systematic way. Examples given are the nucleon deuteron in-medium reaction rates, few-body bound states including the $\ga$-particle, and $\ga$-particle condensation.

Nucleon–deuteron scattering with Δ-isobar excitation

Nucleon–deuteron scattering with Δ-isobar excitation

Nucleon–deuteron breakup: truths and implications

Nucleon–deuteron breakup: truths and implications

Potential independent structure on elastic nucleon–deuteron scattering

Potential independent structure on elastic nucleon–deuteron scattering

Three-nucleon force mediated by Δ-isobar excitation: Application to nucleon–deuteron scattering

Three-nucleon force mediated by Δ-isobar excitation: Application to nucleon–deuteron scattering

Low-energy expansions in nuclear physics

The results of recent experimental and theoretical studies of low-energy nucleon–nucleon and nucleon–deuteron collisions are studied and compared with the older data. Special attention is devoted to two problems: that of the extrapolation of the phase shifts, amplitudes, and cross sections of such collisions to experimentally inaccessible energies, and that of separating the contributions of nuclear and electromagnetic interactions in the parameters of low-energy elastic scattering. Various classical and recent approaches to the solution of these problems are analyzed. A method is developed for constructing low-energy expansions which permits information on the nuclear interaction to be extracted from the measured phase shifts in systems of two and three nucleons or nuclei. The role of electromagnetic corrections to the Coulomb interaction in such scattering reactions can also be studied using this method.

Double Δ production in the γd → pnπ+π− reaction

We have studied the γd → Δ ++ Δ − reaction which requires the collaboration of the two nucleons in deuteron. By means of a model previously developed for the γp → pπ + π − reaction, the two-body exchange currents leading to double delta creation are derived. A fair agreement is obtained with a recent experiment, but more precise measurements and the extension to higher photon energies look advisable in order to see the limits of the present theoretical approach.

Possible interpretation of the ?anomalous? behaviour of the proton spectrum at 0� from the deuteron fragmentation at 9 GeV/c

The momentum spectra of protons, produced at 0° as a result of fragmentation of relativistic deuterons on nuclei, are analyzed. Possible causes of the existing discrepancy of the data on the 0° proton spectrum from the1H(d,p)X reaction at 9.1 GeV/c with results of the impulse approximation calculations are considered. It is shown that taking into account the finite angular resolution of the experimental setup and the corresponding renormalization of the experimental data, on the one hand, and also the inclusion of the additional (to stripping) contribution of protons from the scattering of deuteron nucleons by target protons, on the other, make it possible to match these data with the results of calculations within the framework of the relativistic impulse approximation using the deuteron wave function for the Paris potential.

Fragmentation of 9 GeV/ c deuterons in the region of proton transverse momenta of 0.5–1 GeV/ c and the deuteron wave function at small distances

Momentum spectra of protons emitted at angles of 0.103, 0.139 and 0.157 rad in fragmentation of 9 GeV/ c deuterons on 1H, 2H and 12C nuclei have been measured at the JINR synchrophasotron by using a magnetic spectrometer. It is found that the shape of the high-momentum parts of the spectra is defined only by the deuteron structure and the mechanism of deuteron-nucleon interaction and does not depend on a target. The contributions to the differential cross section of the 1H(d, p)X reaction have been determined, which are conditioned by elastic and inelastic scatterings of deuteron nucleons on a proton, stripping, their interference, and also the excitation of the pion degrees of freedom. In the framework of the light front dynamics, calculations of the proton spectra with the deuteron structure functions for the Paris, Reid soft core, and Bonn potentials have been performed; a better agreement with the experiment is achieved with the deuteron wave function for the Paris potential. A conclusion is made that the nucleons in a deuteron keep their individuality up to relative motion momenta of ∼ 1 GeV/ c.

Interaction of relativistic deuterons with nucleons

The processes of the interaction of fast deuterons with nucleonsdN → pX, when the proton is scattered at a large angle inN − N c.m.s. are analysed. There the wave function of a relativistic deuteron in dynamics of the light cone is used. It is shown that, as in the processes of the deuteron fragmentation type, it is necessary to take into account, the graphs of rescattering and absorption of theπ-meson by a deuteron nucleon, as well as a non-nucleon, quark, degree of freedom in the deuteron. The comparison of the theoretical calculations with the experimental data is performed.

Trinucleon system in a two-body model: Coulomb effect on bound and scattering states.

Recently it has been suggested that as in the neutron deuteron problem the theoretically calculated spin-doublet S wave proton deuteron scattering length /sup 2/a/sub pd/ is correlated with /sup 3/He binding energy. This strongly suggests that /sup 2/a/sub pd/approx. =0. In this paper we study various properties of the low energy trinucleon system including this correlation among scattering length and binding energy for the spin-doublet neutron deuteron and the proton deuteron systems in an ad hoc two-body model. The two-body potential models we employ have a long range tail of r/sup -2/ type and have been parametrized to produce the correct binding energies of /sup 3/H and /sup 3/He and the correct s wave spin-doublet neutron deuteron scattering lengths /sup 2/a/sub nd/. The present study predicts the low energy nucleon deuteron phase shifts and predicts the proton deuteron scattering length to be /sup 2/a/sub pd/approx. =(0.15 +- 0.1) fm.

Possible manifestation of tribaryon resonances in pD backward scattering

It is shown that without taking into account the contributions of tribaryon resonances with masses 3–3.4 GeV there are difficulties in description of the available data on large angle nucleon—deuteron scattering at 0.3–1 GeV. Such tribaryon resonances are really predicted in the model of stretched rotating quark bags.

Scattering from Many Centers in One Dimension

The accuracies of the fixed scatterer approximation (FSA) and the Glauber approximation (GA) are examined for an exactly soluble, one dimensional model which simulates nucleon–nucleus scattering. These approximations are found to work well at unexpectedly low energies. For example, the errors in the FSA and GA for the 'nucleon–deuteron' forward scattering cross section at 10 MeV (laboratory system) are only 5 and 7% respectively. The reason for this success is examined.

The fixed scatterer approximation and nucleon deuteron scattering

A method of solving the Schroedinger Equation for the scattering from two fixed local potentials is presented. The solutions are used within the framework of the fixed scatterer approximation to perform model calculations of N-D scattering using both effective range theory potentials and a “semi-realistic” potential with a strong repulsive core. For smooth potentials approximate solutions to the fixed scatterer problem are proposed and found to be quite accurate. Other procedures for calculating elastic scattering were compared with the exact fixed scatterer approximation. The results show that the neglect of longitudinal momentum transfer in the Glauber multiple diffraction theory is a severe effect except in the forward direction. For small angle scattering the Glauber prediction for the double scattering amplitude is quite accurate, and does not depend strongly upon either the extent of potential overlap, or the ratio V E . Comparisons with the Agassi and Gal results for nonoverlapping potentials indicate that the effects of potential overlap are important, at least for the lowest partial waves. Conclusions about the overall importance of off-energy shell effects in nucleon-deuteron scattering, and about the interference of these effects with the determination of the correlation structure of nuclei are not free from ambiguities.

Additivity of Scattering Phase Shifts

The additivities of the partial wave phase shifts (APP) and of the phase in the impact parameter representation (AIP) are examined for models of scattering from two centers which simulate nucleon–deuteron and pion–deuteron scatterings. It is shown that the AIP, which essentially leads to the Glauber approximation, holds very well, whereas the APP fails except for a trivial case.

The meson exchange current effect in radiative np capture

The pion exchange current contribution to the thermal neutron proton radiative capture cross section is calculated on the basis of potential theory by extracting a local “absorptive exchange potential” from the corresponding fourth order Feynman diagram with the deuteron nucleon vertex on the mass shell. Taking into account that the repulsive core of nucleon interaction leads to modifications not only of the wave functions (which include off-mass shell properties of the deuteron nucleon vertex) but also of this absorptive OPE potential a result is obtained which explains the main part (⋍ 2 3 ) of the well-known 10%-discrepancy between experiment and impulse approximation.