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ABSTRACT: We include two specific three-nucleon-force terms of pion-range–short-range form in our momentum-space calculations for the
three-nucleon continuum. These two terms are expected by chiral perturbation theory to be non-negligible. We study the effects
of these terms in elastic neutron-deuteron scattering and pay special attention to the neutron vector-analyzing power A
y
.
Few-Body Systems 03/2001; 30(1):95-120. · 1.44 Impact Factor
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ABSTRACT: By Faddeev calculations of 3H we study the dependence of the binding energy on the three-nucleon force. We adopt the 2π-exchange Tucson-Melbourne three-nucleon
force and investigate phenomenologically the dependence on the strength of the individual three-body force operators (the
a-, b-, c-, and d-terms). While it is well known that the a-term is not as important as the b- and d-terms to gain the experimental binding energy, we find two solutions for the c-term, one around the value used in the original Tucson-Melbourne model and a new one close to zero. A tensor-analyzing power
T
20 of the pd elastic scattering using the modified Tucson-Melbourne model, which follows the recommendation by chiral perturbation theory
that the short-range c-term should be dropped, describes the data well.
Few-Body Systems 01/2001; 30(1):121-129. · 1.44 Impact Factor
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[show abstract]
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ABSTRACT: We include two new three-nucleon-force terms of pion-range - short-range form in our momentum-space calculations for the three-nucleon continuum. These two terms are expected by chiral perturbation theory to be non-negligible. We study the effects of these terms in elastic neutron-deuteron scattering and pay special attention to the neutron vector analyzing power $A_y$. Comment: 27 pages, latex, 8 figures - fbsart11.sty required - Submitted to Few-Body Systems - Dedicated to the 60th birthday of Walter Gl\"ockle
10/1999;
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ABSTRACT: Quartet n-d scattering lengths are calculated using second-generation nucleon-nucleon potential models. These results are compared to the corresponding quantity recently calculated using chiral perturbation theory. Comment: 4 pages, latex -- Final published version
08/1999;
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ABSTRACT: For several modern nucleon-nucleon potentials state-of-the-art Faddeev calculations are carried out for the nd total cross section between 10 and 300 MeV projectile energy and compared to new high precision measurements. The agreement between theory and data is rather good, with an exception at higher energies where a 10% discrepancy builds up. In addition the convergence of the multiple scattering series incorporated in the Faddeev scheme is studied numerically with the result that rescattering corrections remain important. Based on this multiple scattering series the high energy limit of the total nd cross section is also investigated analytically. In contrast to the naive expectation that the total nd cross section is the sum of the np and nn total cross sections we find additional effects resulting from the rescattering processes, which have different signs and a different behavior as a function of the energy. A shadowing effect in the high energy limit only occurs for energies higher than 300 MeV. The expressions in the high energy limit have qualitatively a similar behavior as the exactly calculated expressions, but can be expected to be valid quantitatively only at much higher energies.
Phys. Rev. C. 01/1999; 59(6).
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ABSTRACT: The polarization-transfer coefficients K
, K
and K
, K
have been measured in the elastic scattering reactions D(, )p and D(, )d at MeV, respectively. They are compared to solutions of the three-nucleon Faddeev equations obtained with the recent nucleon-nucleon
interactions AV18, CD Bonn, NijmI and II. Effects of the Tucson-Melbourne three-nucleon force, adjusted separately to reproduce
the triton binding energy for each of these potentials, are studied. Both and exhibit a scaling behaviour with the triton binding energy. For and the various predictions with two-nucleon forces only agree practically with each other but spread after inclusion of the
three-nucleon force. The agreement of theory and data is fair but the neglect of the proton-proton Coulomb force precludes
a final conclusion.
Few-Body Systems 11/1998; 25(1):133-155. · 1.44 Impact Factor
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ABSTRACT: The longitudinal and transversal asymmetries of the total $\vec{n}\vec{d}$ cross section are calculated. Four modern nucleon-nucleon interactions: AV18, CD Bonn, NijmI and NijmII, give different predictions for these observables. When the three-nucleon Hamiltonian is supplemented by the $2\pi$-exchange Tucson-Melbourne three-nucleon force (3NF), individually adjusted with each particular NN potential to reproduce the experimental triton binding energy, all predictions practically coincide. We propose to check this scaling behavior experimentally in order to get a clear signal for 3NF effects in the low energy three-nucleon continuum. Connected to that is the proposal to measure the energy at which the longitudinal asymmetry goes through zero. This energy is shifted by about 400 keV when 3NF's are acting. Comment: 8 pages in RevTeX, 2 postscript figures
10/1998;
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ABSTRACT: After a brief review of the role three-nucleon forces play in the few-nucleon systems, the chiral-perturbation-theory approach to these forces is discussed. Construction of the (nominal) leading- and subleading-order Born terms and pion-rescattering graphs contributing to two-pion-exchange three-nucleon forces is reviewed, and comparisons are made of the types of such forces that are used today. It is demonstrated that the short-range $c$-term of the Tucson-Melbourne force is unnatural in terms of power counting and should be dropped. The class of two-pion-exchange three-nucleon forces then becomes rather uniform.
10/1998;
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ABSTRACT: The nucleon-deuteron analyzing power $A_y$ in elastic nucleon-deuteron scattering poses a longstanding puzzle. At energies $E_{lab}$ below approximately 30 MeV $A_y$ cannot be described by any realistic NN force. The inclusion of existing three-nucleon forces does not improve the situation. Because of recent questions about the $^3P_J$ NN phases, we examine whether reasonable changes in the NN force can resolve the puzzle. In order to do this we investigate the effect on the $^3P_J$ waves produced by changes in different parts of the potential (viz., the central force, tensor force, etc.), as well as on the 2-body observables and on $A_y$. We find that it is not possible with reasonable changes in the NN potential to increase the 3-body $A_y$ and at the same time to keep the 2-body observables unchanged. We therefore conclude that the $A_y$ puzzle is likely to be solved by new three-nucleon forces, such as those of spin-orbit type, which have not yet been taken into account.
04/1998;
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ABSTRACT: We demonstrate that the partial-wave decomposition of three-nucleon forces used up to now in momentum space has to be necessarily
unstable for high partial waves. This does not affect the applications performed up to now, which were restricted to low partial
waves. We present a new way to perform the partial-wave decomposition free of that defect. This is exemplified for the most
common two-pion-exchange Tucson-Melbourne three-nucleon force. For the lower partial waves the results of the old method are
reproduced.
Few-Body Systems 01/1997; 22(3):107-135. · 1.44 Impact Factor
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ABSTRACT: A new, more efficient approach to include a three nucleon force into three-nucleon continuum calculations is presented. Results obtained in the new and our old approach are compared both for elastic nucleon-deuteron scattering as well as for the breakup process. The advantages of the new scheme are discussed.
12/1996;
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ABSTRACT: We demonstrate that the partial wave decomposition of three-nucleon forces used up to now in momentum space has to be necessarily unstable at high partial waves. This does not affect the applications performed up to now, which were restricted to low partial waves. We present a new way to perform the partial wave decomposition which is free of that defect. This is exemplified for the most often used $2\pi$-exchange Tuscon-Melbourne three-nucleon force. For the lower partial waves the results of the old method are reproduced. Comment: 38 pages in REVTeX, 4 figures in PiCTeX
11/1996;
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ABSTRACT: Data for the neutron-neutron final-state-interaction cross section obtained recently in a kinematically complete neutron-deuteron
breakup experiment have been reanalyzed using rigorous solutions of the three-nucleon Faddeev equations with realistic nucleon-nucleon
interactions. A discrepancy was found with respect to a recent analysis based on the W-matrix approximation to the Paris potential. We also estimate theoretical uncertainties in extracting the neutron-neutron
scattering length resulting from the use of different nucleon-nucleon interactions and the possible action of the two-pion-exchange
three-nucleon force. We find that there exists a certain production angle for the interacting neutron-neutron pair where the
uncertainties become minimal.
Few-Body Systems 06/1996; 20(2):81-92. · 1.44 Impact Factor
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M. Allet,
K. Bodek,
W. Hajdas,
J. Lang,
R. Müller,
S. Navert,
O. Naviliat-Cuncic,
J. Sromicki,
J. Zejma,
L. Jarczyk,
St. Kistryn,
J. Smyrski,
A. Strzalkowski,
H. Witala,
W. Glöckle,
J. Golak, D. Hüber,
H. Kamada
[show abstract]
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ABSTRACT: The proton-deuteron breakup cross sections and analyzing powers A
y
for three kinematically complete configurations in a quasi-free-scattering geometry have been measured at E
lab
P
= 65 MeV. The data are compared with predictions of rigorous Faddeev calculations using the Argonne AV14, Bonn-B, Nijmegen-78,
and Paris potentials. A satisfactory agreement between theory and experimental data, both for cross sections and analyzing
powers, has been found.
Few-Body Systems 04/1996; 20(1):27-40. · 1.44 Impact Factor
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ABSTRACT: The tensor analyzing power Ayy in the symmetric constant relative energy geometry for the dp breakup reaction has been calculated using solutions of the three-nucleon Faddeev equations based on the Argonne AV14, AV18, Bonn-B, Nijm78, Nijm93, NijmI, NijmII, and Paris potentials, as well as the Bonn-B potential in conjunction with the Tucson-Melbourne three-nucleon interaction. The comparison with recent dp data at Ed=94.5 MeV revealed a clear discrepancy in the region where the data exhibit a pronounced structure which is not present in the theoretical results.
Physical Review C 01/1996; · 3.31 Impact Factor
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ABSTRACT: Complex eigenphases and mixing parameters for elastic n-d scattering above the breakup threshold are calculated. Faddeev equations are solved precisely using the Bonn-B NN potential. We point out defects in existing N-d phase-shift analyses. Peculiar energy variations in the mixing parameter η3/2− are shown to have no effect on observables and are simply an artifact of the S-matrix parametrization. It is shown, that the n-d analyzing power A
y
depends most sensitively on the three eigenphases δ1/2
3/2/1, δ2/3
3/2/1, and δ5/2
3/2/1, which again are predominantly generated by the 3
P
j
NN force components. Therefore a determination of those eigenphases from experimental data would help to constrain the 3
P
j
NN forces.
Few-Body Systems 11/1995; 19(4):175-193. · 1.44 Impact Factor
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ABSTRACT: Inclusive electron scattering data on 3He and 3H are analyzed under full treatment of the final state interactions (FSI) using realistic nucleon-nucleon forces. The data are well described. We use two different methods, one where we calculate the pd and ppn breakup contributions separately and another one which is related to the optical theorem for Compton scattering. Both rely on precise solutions of Faddeev-like equations and agree perfectly. The importance of FSI and the inclusion of total isospin T=3/2 for the full breakup of 3He is demonstrated. We also comment on the Coulomb sum rule and the extraction of the proton-proton correlation function.
Physical Review C 10/1995; · 3.31 Impact Factor
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ABSTRACT: Eigenphase shift and mixing parameters for elastic nd scattering below the breakup threshold are compared as determined by the Faddeev theory and the correlated hyperspherical harmonic method. the AV14 NN potential is used. The agreement is very good and the numbers can be considered as benchmarks.
Physical Review C 04/1995; · 3.31 Impact Factor
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ABSTRACT: A new method is presented for solving the Faddeev equations in the three-body continuum, which avoids the moving logarithmic singularities present in momentum space methods used up to now. The new algorithm leads to a simple structure of the Faddeev integral kernel, what simplifies significantly the numerical realization. Its application in nuclear physics is, however, still plagued by the presence of the virtual-state pole in the nucleon-nucleon1S0 channel. Omitting that channel in calculations with the Bonn-B potential we demonstrate excellent agreement between three-nucleon observables obtained with the new and a former method. Since the codes are quite different, this can be considered as a convincing test.
Few-Body Systems 11/1994; 16(4):165-175. · 1.44 Impact Factor
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ABSTRACT: The formalism to include a three-nucleon force into three-nucleon continuum calculations is presented. First numerical results, obtained in momentum space, are shown. The two- and three-nucleon forces have been restricted to act only in the1
S
0 and3
S
1-3
D
1 partial-wave states. As two-nucleon interaction the Bonn-B potential and as three-nucleon interaction the Tucson-Melbourne two-pion exchange model has been used.
Few-Body Systems 01/1993; 14(4):171-190. · 1.44 Impact Factor
