Germanium Wall Research Articles

Experimental Studies of the Coulomb Force Effects in Deuteron-Proton Break-up Reaction at Medium Energy Regime

A set of differential cross-section data of the 1 H(d, pp)n breakup reaction at 130 and 160 MeV deuteron beam energies has been measured in the forward polar angles domain. The data were collected with the use of the Germanium Wall (FZ Julich) and BINA (KVI Groningen) detectors. This part of the phase-space is special with respect to the dominant Coulomb force influence on the system dynamics. The data are compared with the theoretical calculations based on the Argonne V18 potential supplemented with the long-range electromagnetic component. The predictions also include the Urbana IX three nucleon force model. The strongest Coulomb effects are found in regions where the relative energy of the two protons is the smallest.

Investigation of the Deuteron Breakup on Proton Target in the Forward Angular Region at 130 MeV

A set of differential cross-section data of the 1 H(d, pp)n breakup reaction at 130 MeV deuteron beam energy has been measured in the domain of very forward polar angles with the use of the Germanium Wall detector at the Forschungszentrum Julich. The data obtained for over 1000 kinematical points (112 geometries) are compared with the theoretical predictions based on various models of the three-nucleon (3N) dynamics. They comprise: the realistic nucleon-nucleon potentials alone or combined with the three-nucleon force (3NF), the coupled-channel calculations with the explicit treatment of the Δ-isobar excitation and finally, the potentials derived from chiral perturbation theory. In the part of the phase space studied, the Coulomb interaction between protons has a strong impact on the differential cross section of the breakup reaction. The strongest Coulomb effects are found in regions where the relative energy of the two protons is the smallest. In these regions the data are well reproduced exclusively by calculations which include the electromagnetic repulsion between protons. In spite of the dominance of the Coulomb force in the phase space studied, the contribution of 3NF effects is also observed.

Coulomb Force Effects in Deuteron--Proton Breakup Reaction

A large set of cross-section data for the H-1 (d,pp)n breakup reaction was measured at 130 MeV deuteron beam energy with the Germanium Wall setup covering the range of very forward polar angles. In the investigated part of the phase-space, the dynamics is dominated by the Coulomb force influence. The data are compared with results of theoretical calculations based on the realistic Argonne V18 potential supplemented with the long-range electromagnetic component. The predictions also include the Urbana IX three nucleon force model. The cross-section data reveal seizable Coulomb force effects.

Investigation of the Three-Nucleon System Dynamics in the Deuteron–Proton Breakup Reaction

Precise and large sets of cross section, vector A x , A y and tensor A xx , A xy , A yy analyzing power data for the 1 H(d, pp)n breakup reactions were measured at 100 and 130 MeV deuteron beam energies with the SALAD and BINA detectors at KVI and the Germanium Wall setup at FZ-Julich. Results are compared with various theoretical approaches which model the three-nucleon system dynamics. The cross section data reveal a sizable three-nucleon force (3NF) and Coulomb force influence. In case of the analyzing powers very low sensitivity to these effects was found and the data are well describe by 2N models only. For A xy at 130 MeV, serious disagreements were observed when 3NF models are included in the calculations.

Studies of the Three-Nucleon System Dynamics in the Deuteron-Proton Breakup Reaction

One of the most important goals of modern nuclear physics is to contruct nuclear force model which properly describes the experimental data. To develop and test predictions of current models the breakup 1 H(~ d; pp)n reaction was investigated experi- mentally at 100 and 130 MeV deuteron beam energies. Rich set of data for cross section, vector and tensor analyzing powers was obtained with the use of the SALAD and BINA detectors at KVI and Germanium Wall setup at FZ-Julich. Results are compared with var- ious theoretical approaches which describe the three-nucleon (3N) system dynamics. For correct description of the cross section data both, three-nucleon force (3NF) and Coulomb force, have to be included into calculations and influence of those ingredients is seizable at specific parts of the phase space. In case of the vector analyzing powers very low sen- sitivity to any e ects beyond nucleon-nucleon interaction was found. At 130 MeV, the Axy data are not correctly described when 3NF models are included into calculations.

Investigations of Few-Nucleon System Dynamics in Medium Energy Domain

Precise and large set of cross sections, vector A x , A y and tensor A xx , A xy , A yy analyzing powers for the 1 H(d, pp)n breakup reactions were measured at 100 and 130 MeV deuteron beam energies with the use of the SALAD and BINA detectors at KVI and Germanium Wall setup at FZ-Jülich. Results are compared with various theoretical approaches which model the three-nucleon (3N) system dynamics. The calculations are based on different two-nucleon (2N) potentials which can be combined with models of the three-nucleon force (3NF) and other pieces of the dynamics can also be included like the Coulomb interaction and relativistic effects. The cross sections data reveal seizable 3NF and Coulomb force influence. In case of analyzing powers very low sensitivity to the effects was found and the data are well describe by 2N models only. At 130 MeV for A xy serious disagreements appear when 3NF models are included into calculations.

η-PHYSICS AT GEM

Some experimental studies of η–production and η–interactions performed or presently under way by the GEM collaboration at COSY Jülich are reviewed. The Germanium Wall, a stack of annular detectors made of high purity Germanium, was used to measure a series of differential and total cross sections for η–production with proton and deuteron beams on light nuclei. The unique combination of a high resolution magnetic spectrograph (BIG KARL) and 7an electron cooled beam delivered by COSY is ideally suited to perform high precision experiments like the η–mass determination. In a self calibrating experiment three particles from two reactions were detected simultaneously. Kinematical coincidence of 3H and π+ from p + d → 3H + π+ reaction allowed to calibrate the spectrograph and determine the beam momentum with great accuracy. The η–meson was seen clearly as a sharp missing-mass peak on a slowly varying background in the p + d → 3He + X reaction. A new value for the η-mass has been derived with extremely small error bars.

Measurement of [formula omitted] in the S11 resonance

We have measured the reaction p d→ 3 He η at a proton beam energy of 980 MeV, which is 88.5 MeV above threshold using the new `germanium wall' detector system. A missing-mass resolution of the detector system of 2.6% was achieved. The angular distribution of the meson is forward peaked. We found a total cross section of (573 ± 83 (stat.) ± 69 (syst.)) nb. The excitation function for the present reaction is described by a Breit Wigner form with parameters from photoproduction.

A solid-state spectrometer for cooled beams with high acceptance and resolution in space and energy

The GEM detector, a hybrid system consisting of the Germanium Wall and the magnetic spectrometer BIG KARL, was developed to investigate meson production and meson-nucleus interaction with cooled external proton beams from the COSY accelerator at Jülich. The Germanium Wall is a stack of up to four annular position-sensitive semiconductor detectors made from high-purity germanium. Its special structure allows experiments with high counting rates. Design features and results from first test runs with the uncooled COSY beam are presented.