J. J. de Swart

Construction of high-quality NN potential models

We present an updated version (Nijm93) of the Nijmegen soft-core potential, which gives a much better description of the np data than the older version (Nijm78). The chi^2 per datum is 1.87. The configuration-space and momentum-space versions of this potential are exactly equivalent; a unique feature among meson-theoretical potentials. We also present three new NN potential models: a non-local Reid-like Nijmegen potential (NijmI), a local version (NijmII), and an updated regularized version (Reid93) of the Reid soft-core potential. These three potentials all have a nearly optimal chi^2 per datum and can therefore be considered as alternative partial-wave analyses. All potentials contain the proper charge-dependent one-pion-exchange tail. Fortran code for the potentials can be obtained via anonymous ftp from this http URL

Construction of high-quality Nucleon-Nucleon potential models

We present an updated version (Nijm93) of the Nijmegen soft-core potential, which gives a much better description of the np data than the older version (Nijm78). The chi^2 per datum is 1.87. The configuration-space and momentum-space versions of this potential are exactly equivalent; a unique feature among meson-theoretical potentials. We also present three new NN potential models: a non-local Reid-like Nijmegen potential (NijmI), a local version (NijmII), and an updated regularized version (Reid93) of the Reid soft-core potential. These three potentials all have a nearly optimal chi^2 per datum and can therefore be considered as alternative partial-wave analyses. All potentials contain the proper charge-dependent one-pion-exchange tail. Fortran code for the potentials can be obtained via anonymous ftp from this http URL

Chiral two-pion exchange and proton-proton partial-wave analysis

Published in: Phys. Rev. Lett. 82 (1999) 4992-4995 Citing articles (CrossRef) citations recorded in [Science Citation Index] Abstract: The chiral two-pion exchange component of the long-range pp interaction is studied in an energy-dependent partial-wave analysis. We demonstrate its presence and importance, and determine the chiral parameters c_i (i=1,3,4). The values agree well with those obtained from pion-nucleon amplitudes.

PION-NUCLEON COUPLING-CONSTANT

In view of the persisting misunderstandings about the determination of the pion-nucleon coupling constants in the Nijmegen multienergy partial-wave analyses of [ital pp], [ital np], and [ital [bar p]p] scattering data, we present additional information which may clarify several points of discussion. We comment on several recent papers addressing the issue of the pion-nucleon coupling constant and criticizing the Nijmegen analyses.

Determination of the chiral coupling constants c(3) and c(4) in new pp and np partial-wave analyses

As a first result of two new partial-wave analyses, one of the pp and another one of the np scattering data below 500 MeV, we report a study of the long-range chiral two-pion exchange interaction which contains the chiral coupling constants c(1), c(3), and c(4). By using as input a theoretical value for c(1) we are able to determine in pp as well as in np scattering accurate values for c(3) and c(4). The values determined from the pp data and independently from the np data are in very good agreement, indicating the correctness of the chiral two-pion exchange interaction. The weighted averages are c(3)=-4.78(10)/GeV and c(4)=3.96(22)/GeV, where the errors are statistical. The value of c(3) is best determined from the pp data and that of c(4) from the np data.

Effective range theory and the low energy hyperon-nucleon interactions☆

Abstract The effective range theory is treated in the case of coupled channels where allowance is made for channels with higher l-waves. Also it is shown how to take the Coulomb interaction into account. A shape-independent relation connecting the volume integral of the potential and the scattering length is derived. Applying this to the analyses of the light hyperfragments leads to the estimates of the Λ-nucleon scattering lengths: a 0 =− 3.6 +3.6 −1.8 f for S=0 and a 1 =−(0.53±0.12)f for S=1 The low energy Σ−-proton reactions are considered. It is shown how one can take account of the kinematical effects due to the mass differences between the members of the same isomultiplet. We have calculated the effective range parameters for three different potentials corresponding to global (gNNπ = gΣΣπ = gΛΣπ) and antiglobal (gNNπ = −gΣΣπ = −gΛΣπ) symmetry. These are then applied to the Σ−-proton reactions. It is shown that the global symmetry assumption is consistent with the Λ-nucleon scattering lengths, the ratio r R = Σ 0 (Σ 0 + Λ 0 ) obtained in the Σ−-proton reactions and with the data in the K− absorption in deuterium. Also it is shown that the same data rule out the antiglobal symmetry assumption.

Electromagnetic corrections to the one-pion-exchange potential

Leading-order electromagnetic loop corrections to the one-pion-exchange potential are computed within the framework of chiral perturbation theory. These corrections generate an effective nucleon-nucleon potential, V{sub {pi}{gamma}} , which supplements the sum of one-pion-exchange potential and the nucleon-nucleon Coulomb potential. This potential is charge dependent and its construction is demonstrated to be gauge invariant. The potential V{sub {pi}{gamma}} has been included in the Nijmegen partial-wave analysis of np data. A particular renormalization scheme is chosen that leads to a negligible change in the {pi}{sup {plus_minus}}NN coupling constant and in the np {sup 1}S{sub 0} scattering length and effective range. {copyright} {ital 1998} {ital The American Physical Society}

A potential model for hyperon--nucleon scattering

Abstract Low energy ΛN- and ΣN-scattering has been calculated in a potential model by solving the multichannel Schrodinger equation. Meson theoretic potentials are used which describe the exchange of nonets of pseudoscalar and vector mesons and uncorrelated two pion exchange. At short distances hard cores are employed. Coupling constants are taken from SU(3), SU(6), and the conserved current theory for vector mesons. Coulomb effects are included and different baryon masses within isomultiplets are considered. Charge symmetry breaking between the Λp- and Λn-channel due to one pion and one rho exchange has been taken into account. The model is checked in nucleon-nucleon scattering where it gives a good qualitative description of the NN-phaseshifts below the pion production threshold. A least-squares fit to the low energy Λp, Σ+p, and Σ−p data yields a very satisfactory result. The model leads then to the low energy parameters of Σ+p: a 8 c = −2.42 ± 0.30 fm , r 8 c = 3.41 ± 0.30 fm a t c = + 0.71 fm , r t c = −0.78 fm . The scattering lengths a and effective ranges r for Λp are a 8 p = −2.16 ± 0.26 fm , r 8 p = 2.03 ± 0.10 fm a t p = − 1.32 ± 0.07 fm , r t p = 2.31 ± 0.08 fm . and for Λn a 8 n = −2.67 ± 0.35 fm , r 8 n = 2.04 ± 0.10 fm a t n = − 1.02 ± 0.05 fm , r t p = 2.55 ± 0.10 fm . The possible existence of 2S1 resonances in the neighborhood of the ΣN thresholds is discussed. Coupled channel effective range expansions are given around the ΣN-thresholds.

Triton calculations with the new Nijmegen potentials

Abstract Triton properties are calculated using new nucleon-nucleon potentials, which were fit to the world nucleon-nucleon data. Three of these models have a nearly optimal χ 2 per degree of freedom and can therefore be considered as alternative partial-wave analyses, which in quality can almost compete with the Nijmegen partial-wave analysis. The triton binding energy obtained with three local models (Nijm II, Reid93, AV18) can be summarized as 7.62 ± 0.01 MeV, which is nearly 900 keV lower than experiment. The non-local model Nijm I binds by 7.72 MeV.

ANTIPROTON-PROTON PARTIAL-WAVE ANALYSIS BELOW 925 MEV/C

Partial-wave analyses (PWAs) have a long history in the fields of πN and NN scattering. Due to the poor quality of low-energy antiproton beams and the resulting absence of accurate experimental data, analogous model-independent studies of the much more complex \(\bar pp\) system have in the past always been impossible. In recent years, however, experimental progress has been very significant, in particular due to the coming in 1983 of the Low-Energy Antiproton Ring (LEAR) facility at CERN. While in the pre-LEAR era spin-dependent observables and charge-exchange (\(\bar pp \to \bar nn\)) data were almost nonexistent, the situation between 400 and 925 MeV/c is now quite good: the LEAR collaborations PS172, PS173, PS198, and PS199 have measured a variety of observables with impressive accuracy. High-quality analyzing-power data have been obtained for the elastic [1] and charge-exchange [2] reactions. Very recently, even charge-exchange depolarization data have become available [3]. Unfortunately, the practical difficulties involved in constructing a high-quality “cooled” antiproton beam of lower momentum are large. Consequently, the \(\bar pp\) database below about 400 MeV/c is still by far not as good as one would like, in striking contrast to the pp case where very accurate data exist as low as T L = 0.35 MeV (P L = 25 MeV/c). It also remains an outstanding experimental challenge to construct a polarized antiproton beam to further probe the spin structure of the interaction.