The quasi-free scattering reactions 11C(p,2p) and 10,11,12C(p,pn) have been studied in inverse kinematics at beam energies of 300–400 MeV/u at the R3B-LAND setup. The outgoing proton-proton and ...proton-neutron pairs were detected in coincidence with the reaction fragments in kinematically complete measurements. The efficiency to detect these pairs has been obtained from GEANT4 simulations which were tested using the 12C(p,2p) and 12C(p,pn) reactions. Experimental cross sections and momentum distributions have been obtained and compared to DWIA calculations based on eikonal theory. The new results reported here are combined with previously published cross sections for quasi-free scattering from oxygen and nitrogen isotopes and together they enable a systematic study of the reduction of single-particle strength compared to predictions of the shell model over a wide neutron-to-proton asymmetry range. The combined reduction factors show a weak or no dependence on isospin asymmetry, in contrast to the strong dependency reported in nucleon-removal reactions induced by nuclear targets at lower energies. However, the reduction factors for (p,2p) are found to be 'significantly smaller than for (p,pn) reactions for all investigated nuclei.
In the past two decades, several laboratories have produced a large amount of data for cross sections, analyzing powers, and other spin observables from various reactions in the three-nucleon system. ...The experimental results are moderately described by only using the two-nucleon potentials in Faddeev-type calculations. The remaining discrepancies should, in principle, and aside from Coulomb and relativistic effects, be removed once the effects of three-nucleon forces are implemented. High precision data on elastic and break-up reactions show, however, that even after the inclusion of these effects, the picture is not complete yet and some ingredients are still missing in the calculations. With the advent of new frameworks within which two and three-nucleon forces can be properly implemented in the calculation of observables in heavy nuclei, it is essential that these forces are better understood.
A measurement of the analyzing powers for the
2
H
(
p
→
,
p
p
)
n
break-up reaction was carried out at KVI exploiting a polarized-proton beam at an energy of
135
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
4
π
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.
We present measurements of differential cross sections and analyzing powers for the elastic
2
H
(
d
,
d
)
d
scattering process. The data were obtained using a 130 MeV polarized deuteron beam. Cross ...sections and spin observables of the elastic scattering process were measured at the AGOR facility at KVI using two independent setups, namely BINA and BBS. The data harvest at setups are in excellent agreement with each other and allowed us to carry out a thorough systematic analysis to provide the most accurate data in elastic deuteron-deuteron scattering at intermediate energies. The results can be used to confront upcoming state-of-the-art calculations in the four-nucleon scattering domain, and will, thereby, provide further insights in the dynamics of three- and four-nucleon forces in few-nucleon systems.
Understanding of the exact nature of three-nucleon forces is the most challenging topic in the field of nuclear physics. Three-nucleon break-up reaction is a good tool to look into the underlying ...dynamics of the nuclear force, thanks to its rich kinematical phase space which has different levels of sensitivity to three-nucleon force effects. The recent studies on few-nucleon systems have revealed that the current nuclear force models cannot describe nucleon-deuteron scattering data accurately. In the present work, the analyzing powers of the proton-deuteron break-up reaction obtained using a 190 MeV polarized proton beam will be discussed. We present for the first time the vector analyzing powers for the kinematics in which one of the protons scatters to intermediate and large scattering angles at this energy. The results show a fairly good agreement with various theoretical predictions for both intermediate and large scattering angles of the break-up phase space.
The presented work focuses on the development of a differential pumping system using double-sided silicon-strip detectors to separate the ultra-high vacuum of a storage ring from subsequent detectors ...and outgassing components placed in an auxiliary vacuum. Such a technical concept will give the opportunity to use telescope-like detector systems in an ultra-high vacuum environment, such as a storage ring, without enclosing the entire system in a pocket. Therefore, it will enable the detection of recoil particles with the smallest possible energy due to the use of the innermost strip detector as an active window. Our results prove that such an assembly is feasible without having an effect, within experimental errors, on the performance of the strip detector. Vacuum separation better than six orders of magnitude was achieved with the ultra-high vacuum side reaching down to the
10
−
10
mbar
pressure region.
Systems of three nucleons (3N) can be treated as a testing ground for modern approaches to describe nuclear interactions. At intermediate energies, observables for 3N systems are sensitive to subtle ...effects of the dynamics beyond the pairwise nucleon–nucleon force, so-called 3N-force (3NF). For years the search for 3NF has been motivating precise measurements of observables of elastic nucleon–deuteron scattering and for the deuteron breakup reaction. Breakup of a deuteron in collision with a proton leads to the final state of three free nucleons, with variety of possible kinematic configurations, revealing locally enhanced sensitivity to particular aspects of the interaction dynamics, like 3NF, Coulomb force between protons, or relativistic effects. This feature makes the breakup reaction a very versatile tool for validation of the theoretical description. Reactions involving four nucleons pose immense challenges with regard to exact theoretical calculations for such systems. Nonetheless, they attract attention due to expected enhanced sensitivity to certain aspects of the nuclear dynamics, manifesting themselves in various channels and configurations. The most important results of recent experimental studies of 3N and 4N systems at intermediate energies are discussed. A brief survey of the ongoing projects is given.
Direct high-precision mass spectrometry of the heaviest elements with SHIPTRAP, at GSI in Darmstadt, Germany, requires high efficiency to deal with the low production rates of such exotic nuclides. A ...second-generation gas stopping cell, operating at cryogenic temperatures, was developed and recently integrated into the relocated system to boost the overall efficiency. Offline measurements using 223Ra and 225Ac recoil-ion sources placed inside the gas volume were performed to characterize the gas stopping cell with respect to purity and extraction efficiency. In addition, a first online test using the fusion-evaporation residue 254No was performed, resulting in a combined stopping and extraction efficiency of 33(5)%. An extraction time of 55(44)ms was achieved. The overall efficiency of SHIPTRAP for fusion-evaporation reaction products was increased by an order of magnitude to 6(1)%. This will pave the way for direct mass spectrometry of heavier and more exotic nuclei, eventually in the region of superheavy elements with proton numbers Z⩾104.
Precision data are presented for the break-up reaction, H2(p→,pp)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 H2(p→,He2)n channel. These results are compared to the H2(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.
NeuLAND (New Large-Area Neutron Detector) is the neutron detector for the R3B-experiment (Reactions with Relativistic Radioactive Beams) at FAIR (Facility for Anti-proton and Ion Research). NeuLAND ...is a fully active detector composed of plastic scintillator bars. Neutrons are detected by the production of charged particles in the scintillators through hadronic scattering. These charged particles are then detected by their scintillation light. Due to the highly granular design of NeuLAND, the primary neutron interaction points can be accurately reconstructed. These reconstructed points contribute to a kinematically complete reconstruction of reactions with relativistic heavy-ion beams in the target, the goal of the R3B-experiment. However, charged particles produced by scattering on other parts of the R3B-setup may provide a significant background. To distinguish the target neutrons from the background, a VETO detector could be placed in front of NeuLAND. This VETO detector is a single plane of thin plastic scintillator bars. It, therefore, provides a high detection efficiency for background particles, but a low detection efficiency for neutrons. For every signal in the VETO, NeuLAND signals can be analyzed with respect to their correlation to the VETO signal and can be eliminated from the further neutron analysis. In this paper, the design of this VETO detector is discussed.
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