Effect Of Tensor Force Research Articles

Nonmesonic decay of heavyΛhypernuclei

We have calculated the ratio of the rate for nonmesonic decay of the $\ensuremath{\Lambda}$ in nuclear matter to that of the free $\ensuremath{\Lambda}$ decay rate using a pion and rho meson exchange model. Including tensor force effects and a final-state correlation function generated from the Reid-soft-core potential, we estimate $\frac{{\ensuremath{\Gamma}}_{\mathrm{nm}}}{{\ensuremath{\Gamma}}_{\mathrm{free}}}$ to be of order 1. A discrepancy with respect to the prior estimate of Adams is resolved.

Deuteron form factors and the tensor force

Results of a non-relativistic calculation of deuteron form factors are presented for separable potentials with and without tensor force. The tensor term in triplet state is added in such a way as to keep the values of deuteron binding energy,a t andr 0t unaltered, so that the difference in the form factors can be regarded as the effect of tensor force only. The calculation has been performed for two different shapes of separable potentials and for three differentD-state probabilities to study their comparative effect.

Effect of quark-quark tensor and spin-spin force on the radiative decay of Δ-isobar

We use oscillator wavefunctions with Coulomb, finite-range spin-spin and harmonic confinement forces, stabilizing the nucleon and the isobar separately. Subsequent introduction of the Fermi-Breit tensor force leads to an E(2) M(1) ratio in the Δ-;Nγ decay. The sign and magnitude of this ratio is interesting and it is shown that its measurement leads to an estimate of α s in light hadrons.

Tensor Force Effect on B -Difference between 4He and 4H

Tensor Force Effect on B -Difference between 4He and 4H

Correlations between potentials and observables in the NN interaction

We study the effects of the components of the soft-core and velocity-dependent Paris nucleon-nucleon potential on the scattering observables for laboratory energies, T L, between 10 and 350 MeV. Knowledge of these correlations is useful to indicate constraints on components of the nucléon-nucléon force. The velocity-dependent component, attractive at low energy and repulsive at high energy, plays a role at all energies. The polarisation P, the depolarisation D and the parameters D t, A, R, C KP and C NN are good tests for the tensor, spin-orbit and, to a smaller extent, quadratic spin-orbit forces. The isovector tensor force contribution is important at low energy and that of the isovector spin-orbit at high energy. The isoscalar tensor force effect is large at all energies and that of the isoscalar spin-orbit force rather small. The potential without quadratic spin-orbit term reproduces well the experimental data for T L < 150 MeV.

An investigation of the tensor force effects on the spin-orbit splitting in spherical and very deformed nuclei

A contribution of the tensor force to the phenomenological spin-orbit (SO) potential in the single-particle Hamiltonian is studied for spherical and deformed rare-earth and actinide nuclei. It is found that the deformation dependence of the SO coupling constant, suggested by the second order tensor force contribution, enables to explain the observed single particle (s.p.) states in the second minimum of237Pu and239Pu using a SO strength weaker than usually applied. Consequences of the tensor contributions for the stability of theZ=114 superheavy nucleus are studied.

Sum rules for Landau parameters in nuclear matter

The Pauli principle sum rules for the Landau parameters in nuclear matter are derived, including the effects of tensor forces.

The role of tensor forces in Fermi liquid theory

We study the effect of tensor forces on the Fermi liquid parameters in nuclear matter. The usual stability conditions in the σ 1 · σ 2and σ 1 · σ 2 τ 1 · τ 2 channels are found to be appreciably modified by tensor forces. We present Fermi liquid parameters for the Reid soft-core potential corrected for the proper inclusion of tensor forces.

Spin forces in charmonium spectroscopy

The observed ${\ensuremath{\psi}}^{\ensuremath{'}}(3.68)\ensuremath{-}{\ensuremath{\psi}}^{\ensuremath{'}\ensuremath{'}}(3.77)$ structure in ${e}^{+}{e}^{\ensuremath{-}}$ annihilation implies the existence of a tensor-force effect in charmonium spectroscopy. We show that the magnitude of the effect is consistent with an analysis of $^{3}P_{J}$ levels using a phenomenological Hamiltonian linear in both $\stackrel{\ensuremath{\rightarrow}}{\mathrm{L}}\ifmmode\cdot\else\textperiodcentered\fi{}\stackrel{\ensuremath{\rightarrow}}{\mathrm{S}}$ and ${S}_{12}$, the tensor force. Adding a linear ${\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\sigma}}}_{1}\ifmmode\cdot\else\textperiodcentered\fi{}{\stackrel{\ensuremath{\rightarrow}}{\ensuremath{\sigma}}}_{2}$ term one can account for all known charmonium levels below 4 GeV and predict the location of the rest of the spectrum, in particular the $^{1}P_{1}$ state at 3.27 GeV.

Bound states of charmed baryons and antibaryons

Within the framework of nonrelativistic potential models, we investigate the possibility that bound states of the type B-bar/sub c/B/sub c/ may exist, where B/sub c/ is a charmed member of the 20 baryon multiplet of SU(4). By rather general considerations, we establish the approximate level order of the bound-state spectrum. Specific potential models are then invoked to qualitatively estimate the binding energies and rms radii of B-bar/sub c/B/sub c/ bound states. For reasonably small binding energies ( or =0.7 fm) than the corresponding c-barc quark-model states. We show that most of the low-lying states are isospin I = 0 as in the c-barc model. However, because of the coherent effect of tensor forces, certain I = 1 configurations of the C-bar/sub 1/C/sub 1/ system experience a downward energy shift, and hence could appear in the same energy region as I = 0 states (e.g., /sup 2I ts(ts1,2S/L/sub J/ = /sup 33/P/sub 0/ state near /sup 13/P/sub 0,1,2/ states). The states we describe can mix with and modify the properties of c-barc quark states ofmore » the same quantum numbers in the J/psi,chi,psi' region from 3.1 to 3.7 GeV. Some of them could appear independently as narrow states in the mass region of 4 GeV. ''Exotic'' C-bar/sub 1/C/sub 1/ states with I = 2 are shown to always lie above I = 0,1 configurations of the same L; however, for a wide class of potential models, the P-wave C-bar/sub 1/C/sub 1/ states (/sup 53/P/sub 0,1,2/,/sup 51/P/sub 1/) are still bound close to threshold (approx.4.8 GeV). We exhibit qualitative arguments that some of these B-bar/sub c/B/sub c/ bound states may be narrow. We discuss possible experimental means for finding the I = 1 and 2 states, i.e., those not predicted by the cc-bar quark model.« less

Polarization transfer in deuteron elastic scattering and the deuteron-nucleus tensor interaction

Abstract It is shown that the angular distributions of the polarization transfer coefficients contain new complementary information on the tensor part of the deuteron-nucleus interaction which cannot be obtained solely from tensor analyzing power measurements. Using a formalism where the polarization quantities carry definite spin-flip quantum numbers we derive the linear combinations of observables expected to be more sensitive to tensor force effects. The way they can help to distinguish between different types of tensor potentials is briefly discussed.

Effects of Tensor Force in Localized Neutron System

Effects of Tensor Force in Localized Neutron System

Effect of tensor force and one-nucleon exchange in the quasielastic ( 6Li, 6He) reaction

The effect of the tensor force and one-nucleon exchange is studied by applying the antisymmetrized DWBA method to the 48Ca( 6 Li, 6He) 48 Sc(π f 7 2 ν f 7 2 −1) J reaction. The exchange effect increases the cross sections but does not change the angular shapes. In contrast to the tensor force with Gaussian shape, the TWOPEP tensor contribution is larger than that of the central force and dominates the reaction for large L-transfer.

On a simplified effective neutron-proton interaction including core-polarization effects for odd-odd deformed nuclei

It is well known that the description of odd-odd deformed nuclei is not satisfactory if the usual one-parameter δ-force is used as the residual neutron-proton interaction. In this letter we show that, starting with a simple δ force, an improvement can be obtained which takes into account polarization effects of the core, as well as possible tensor and spin-orbit force effects, and which introduces only one additional parameter. This improvement is even better than that obtained with a finite range central-plus-tensor force, which introduces four additional parameters.

On a simplified effective neutron-proton interaction including core-polarization effects for odd-odd deformed nuclei

It is well known that the description of odd-odd deformed nuclei is not satisfactory if the usual one-parameter δ-force is used as the residual neutron-proton interaction. In this letter we show that, starting with a simple δ force, an improvement can be obtained which takes into account polarization effects of the core, as well as possible tensor and spin-orbit force effects, and which introduces only one additional parameter. This improvement is even better than that obtained with a finite range central-plus-tensor force, which introduces four additional parameters.

Effect of vector and tensor forces in the excitation of [formula omitted] states in the 40Ca (p,p′) 40Ca ∗ reaction

The results of microscopic distorted wave approximation calculations for f 7 2 - d 3 2 −1 excitations in the 40Ca(p,p′) 40Ca ∗ reaction are presented. A “realistic” effective interaction with central, tensor, and spin-orbit components is considered. Some evidence for the tensor force is found in the data from a recent experiment.

Simultaneous effect of P-wave interactions and tensor force on the polarization in N-d scattering

A three-body calculation is performed at E n = 14.1 MeV for the n-d elastic scattering which takes into account the 1S 0, 3S 1− 3D 1, 1P 1, 3P 0, 3P 1 and 3P 2 components of the nucleon-nucleon interaction. Good agreement with experimental data is obtained for the differential cross section and neutron polarization. The deuteron polarizations are also qualitatively reproduced.

Effect of tensor forces on composition of dense matter

Two models of hyperonic matter, in which the ( 3 S 1− 3 D 1) tensor forces are treated explicitly through short range tensor correlations, are studied with variational method. The results indicate that at high densities matter consists of neutrons only, while at low densities a few percent admixture of other particles may occur.

Effect of tensor forces on the charge form factor of the α-particle

Abstract We calculate the charge form factor of the α-particle using Irving and Gaussian forms for the radial wave functions. The ground state is assumed to be a mixture of the principal 1 S 0 and the principal 5 D 0 states. The parameters in the wave functions have been determined from the variational calculations of the binding energy. We find that our calculations using the Irving wave function show good agreement with electron-helium scattering experiments and with calculations using hard-core potentials upto 10 fm −2 transfer of the square of the momentum. The agreement is comparatively poor for the Gaussian wave function.

ΛNTensor Forces for Scattering and for theΛ-Particle Binding in Nuclear Matter

The effect of ΛN tensor forces on the Λ-particle binding in nuclear matter is studied with the use of second-order perturbation theory and the Brueckner-Bethe reaction-matrix approach in the g-matrix approximation. The g matrix is calculated self-consistently by use of the Kallio-Day version of the reference-spectrum method. The free kinetic energies are assumed for the unoccupied states. One-boson-exchange (OBE) models indicate that the ΛN tensor force is expected to be of short range and moderate strength. For short-range tensor forces the dominant momentum components are very large, and the effects of such forces are only slightly modified by the nuclear medium. On the other hand, if the ΛN tensor forces were of rather long range, they would be quite strongly suppressed in nuclear matter. These features are very clearly exhibited by consideration of the effective nonlocal central potentials that represent the (s-state) effect of tensor forces for nuclear matter and for scattering. The ratio of the (nuclear-matter) expectation values of these two effective potentials is a good measure of the suppression. The expectation value of the effective potential for nuclear matter is just the second-order perturbation-theory energy. Reaction-matrix calculations show that higher-order effects may become quite important for shorter ranges. Such calculations have, in particular, been made for various mixtures of central and tensor forces chosen to give a constant s-wave scattering length. Yukawa shapes corresponding to the kaon and one- and two-pion masses were used, as well as realistic OBE potentials with a hard core and a tensor component due to kaon exchange (and also approximately due to η exchange). For a particular mixture, the suppression is measured by the reduction in the well depth relative to the depth for a purely central potential which has the same hard core and the same scattering length and effective range as the mixture. For the short-range tensor forces there is rather little suppression even for very strong tensor forces which account for all the triplet scattering. Different assumptions about the d-state interaction have an almost negligible effect on the s-state well depth if the same assumption is made for both scattering and nuclear matter. Similar considerations are made for the effect of tensor forces in the p wave, for which we find very little suppression (≲1 MeV). We conclude that if central and short-range tensor forces are chosen to compensate each other for low-energy scattering, they will also compensate each other quite closely for nuclear matter. In particular, for the OBE potentials with strengths consistent with the phenomenological values of the ΛNK¯ coupling constants, the reduction in the well depth is at most about 4 MeV. The conclusions about the ΛN interaction obtained from a comparison of the calculated and phenomenological well depths are, therefore, effectively unchanged by the presence of a ΛN tensor force. Consequently, in order to bring the two numbers into agreement, it is necessary to invoke a substantial short-range repulsion, a rather weak p-state interaction, and suppression of the ΛN−ΣN coupling and/or repulsive ΛNN three-body forces.