Polarisation in neutron-deutron scattering at 30 MeV

Dobiasch, H.; Fischer, Ralf; Haesner, B.; Klages, H.O.; Schwarz, Philip J.; Zetnitz, B.; Maschuw, R.; Sinram, K.; Wick, K.

doi:10.1016/0370-2693(78)90273-3

Cited by 16 publications

(13 citation statements)

References 5 publications

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“…Meanwhile, the 30-MeV n-d data of Ref. [18] show a significantly lower RD, of about 13%. We conclude that both p-d and n-d A y (θ ) follow a closely similar trend for the discrepancy between data and theory.…”

Section: Results and Conclusionmentioning

confidence: 87%

“…[18] show that there is still a 3N APP at this energy but that the RD is significantly diminished to ≈13%. The lack of n-d A y (θ ) data between 16 and 30 MeV motivated us to perform measurements in this region, to better characterize the energy dependence of the 3N APP and to provide data to aid the theoretical development of NN and 3N potential models.…”

Section: Introductionmentioning

confidence: 86%

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Neutron-deuteron analyzing power data atEn=22.5MeV

et al. 2014

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We present measurements of n-d analyzing power, A y (θ), at E n = 22.5 MeV. The experiment uses a shielded neutron source which produced polarized neutrons via the 2 H( d, n) 3 He reaction. It also uses a deuterated liquidscintillator center detector and six pairs of liquid-scintillator neutron side detectors. Elastic neutron scattering events are identified by using time-of-flight techniques and by setting a window in the center detector pulse-height spectrum. The beam polarization is monitored by using a high-pressure helium gas cell and an additional pair of liquid-scintillator side detectors. The n-d A y (θ) data were corrected for finite-geometry and multiple-scattering effects using a Monte Carlo simulation of the experiment. The 22.5-MeV data demonstrate that the three-nucleon analyzing power puzzle also exists at this energy. They show a significant discrepancy with predictions of highprecision nucleon-nucleon potentials alone or combined with Tucscon-Melbourne or Urbana IX three-nucleon forces, as well as currently available effective-field theory based potentials of next-to-next-to-next-to-leading order.

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Section: Results and Conclusionmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 86%

Neutron-deuteron analyzing power data atEn=22.5MeV

et al. 2014

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“…The 30 MeV data of Ref. [16] demonstrated that there is still a 3NAPP at this energy, but suggested that the relative difference between theory and experiment is significantly less, about 13%. (Available p-d A y (θ ) data at 30 MeV agree within uncertainties, providing a relative difference of 15%.)…”

Section: Introductionmentioning

confidence: 95%

“…One proposed explanation was that the 3 P J phase shifts are incorrect, leading to an improper determination of the NN force components in these partial waves [19]. For a short time, chiral perturbation theory seemed to confirm this; [16] calculations in the next-to-leading order (NLO) suggested that the NN chiral force will solve the 3NAPP via modified 3 P J phase shifts [20]. However, it soon became clear that the 3 P J phase shifts cannot be improved such that they fit all of the existing 2N and 3N data.…”

Section: Introductionmentioning

confidence: 99%

Neutron-deuteron analyzing power data at 19.0 MeV

et al. 2010

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Measurements of neutron-deuteron (n-d) analyzing power A y (θ) at E n = 19.0 MeV are reported at 16 angles from θ c.m. = 46.7 to 152.0 • . The objective of the experiment is to better characterize the discrepancies between n-d data and the predictions of three-nucleon calculations for neutron energies above 16.0 MeV. The experiment used a shielded neutron source, which produced polarized neutrons via the 2 H( d, n) 3 He reaction, a deuterated liquid scintillator center detector (CD) and liquid-scintillator neutron side detectors. A coincidence between the CD and the side detectors isolated the elastic-scattering events. The CD pulse height spectrum associated with each side detector was sorted by using pulse-shape discrimination, time-of-flight techniques, and by removing accidental coincidences. A Monte Carlo computer simulation of the experiment accounted for effects due to finite geometry, multiple scattering, and CD edge effects. The resulting high-precision data (with absolute uncertainties ranging from 0.0022 to 0.0132) have a somewhat lower discrepancy with the predictions of three-body calculations, as compared to those found at lower energies.

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“…To emphasize this, we plot in Fig. 4 the values of A y (θ ) at θ = 90 • and those at θ max as a function of the incident neutron energy E n , comparing them with values extracted from the experimental data [17][18][19][20][21]. This figure clearly shows that the effect of the SO-3NF, which is displayed by the difference between the AV18+BR 680 and the AV18+BR 680 +SO calculations, tends to improve A y (θ ) dominantly at both angles.…”

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confidence: 99%

Spin-dependent three-nucleon force effects on nucleon-deuteron scattering

Ishikawa

2007

Phys. Rev. C

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We construct a phenomenological three-nucleon force (3NF) model that gives a good description of polarization observables in elastic nucleon-deuteron (N -d) scattering at a low energy together with a realistic nucleon-nucleon force and a 3NF arising from the exchange of two pions. Parameters of the model, which consists of spinindependent, spin-orbit, and tensor components, are determined to reproduce the three-nucleon binding energy and polarization observables in N -d scattering at 3 MeV. Predictions of the 3NF model on N -d polarization observables at higher energies are examined, and the effects of each component on the observables are investigated. As is well known, modern two-nucleon force (2NF) models have a deficiency in explaining the binding energies of three-nucleon (3N) systems, and this problem is successfully solved by introducing a 3NF arising from the exchange process of two pions among three nucleons, which is called the two-pion-exchange (2π E) 3NF [1,2]. However, such combinations of the 2NFs and the 2π E-3NF that reproduce the 3N binding energy do not necessarily explain polarization observables in 3N scattering systems such as vector or tensor analyzing powers in elastic N -d scattering. See, e.g., Table III of Ref. [3], where calculations of observables with and without a 2π E-3NF are compared in terms of χ 2 with experimental data below 30 MeV of incident nucleon energy in the laboratory system. In spite of recent progress in constructing realistic 3NFs from chiral effective field theory or from heavier-boson-exchange mechanisms, no consensus has been obtained for possible mechanisms of 3NFs consistent with all of the experimental data. On the other hand, model 3NFs with artificial functional forms have been proposed to explain the polarization observables quite well [4][5][6]. These 3NFs have a form that typical components in 2NFs, e.g., central spin-independent, tensor, or spin-orbit components, are modified in the presence of third nucleon. [See Eq. (1) below.]In this paper, we introduce such a phenomenological 3NF to resolve the discrepancies of a 2NF and the 2π E-3NF at a low energy, and we examine whether it is still valid for N -d observables at higher energies up to 30 MeV. Since it may not be so difficult to understand what physical process is simulated by the spin dependence of each component, we expect that the present study will provide some hint of which characteristics of more realistic 3NFs should be studied.Our 3N calculations are based on a formalism to solve the Faddeev equations in coordinate space as integral equations [7,8]. For scattering states below the 3N breakup threshold energy, effects of the long-range Coulomb force between two * ishikawa@hosei.ac.jp protons are exactly treated [9]. Calculations for energies above the 3N breakup threshold are formulated in Ref. [10]. 3N partial wave states for which 2NFs and 3NFs act, are restricted to those with total two-nucleon angular momenta j 6 for bound state calculations, and j 3 for scattering state calculations. The ...

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Polarisation in neutron-deutron scattering at 30 MeV

Cited by 16 publications

References 5 publications

Neutron-deuteron analyzing power data atEn=22.5MeV

Neutron-deuteron analyzing power data atEn=22.5MeV

Neutron-deuteron analyzing power data at 19.0 MeV

Spin-dependent three-nucleon force effects on nucleon-deuteron scattering

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