Vector Analyzing Power Data Research Articles

An investigation of p+8He elastic scattering

The vector analyzing power and differential cross-section for the elastic scattering of 8 He nucleus from polarized protons at 71 MeV/nucleon have been analyzed in the framework of the optical model potentials. Microscopic single folding (SF) optical potentials (OP) have been constructed based upon two different effective nucleon–nucleon (NN) interactions, namely Jeukenne–Lejeune–Mahaux (JLM) and BDM3Y1 effective interactions. The effect of 8 He nuclear structure has been tested through two different choices of the nuclear density distribution. It is concluded that the nucleus 8 He may be considered as a thick skin exotic nucleus. In order to investigate the vector analyzing power data, besides the Thomas phenomenological representation, three different forms of the spin–orbit (SO) part of the OP have been considered. These forms are based directly or indirectly upon the density distribution of 8 He nucleus. It is found that SO potentials of larger root mean square radii are able to successfully describe the vector analyzing power data more than those of shorter radii.

Vector analyzing powers of the deuteron-proton elastic scattering and breakup at 100 MeV

High-quality vector analyzing power data for the 1 H(d,pp)n breakup reaction and elastic scattering at 100MeV beam energy have been measured in a large part of the phase space for these processes. The results are compared to theoretical predictions obtained using the charge-dependent Bonn potential alone or combined with the three-nucleon force TM99 as well as to the results of calculations in the coupled-channel approach, with or without the inclusion of the Coulomb interaction. In the studied observables, effects of the 3NF and the Coulomb force are almost absent. The pairwise NN interactions alone are sufficient to describe the experimental results.

Vector and tensor analyzing powers in deuteron-proton breakup reaction

High precision data for vector and tensor analyzing powers of the 1H(d⃗,pp)n breakup reaction at 130 and 100 MeV deuteron beam energies have been measured in a large fraction of the phase space. They are compared to the theoretical predictions based on various approaches to describe the three nucleon (3N) system dynamics. Theoretical predictions describe very well the vector analyzing power data, with no need to include any three-nucleon force effects for these observables. Tensor analyzing powers can be also very well reproduced by calculations in most of the studied region, but locally certain discrepancies are observed. At 130 MeV for Axy such discrepancies usually appear, or are enhanced, when model 3N forces are included. Predicted effects of 3NFs are much lower at 100 MeV and at this energy equally good consistency between the data and the calculations is obtained with or without 3NFs.

Vector analyzing powers of deuteron-proton elastic scattering and breakup at 130 MeV

High-quality vector analyzing power data for the 1 H(d,pp)n breakup reaction and elastic scattering at 100MeV beam energy have been measured in a large part of the phase space for these processes. The results are compared to theoretical predictions obtained using the charge-dependent Bonn potential alone or combined with the three-nucleon force TM99 as well as to the results of calculations in the coupled-channel approach, with or without the inclusion of the Coulomb interaction. In the studied observables, effects of the 3NF and the Coulomb force are almost absent. The pairwise NN interactions alone are sufficient to describe the experimental results.

Vector and tensor analyzing powers in deuteron-proton breakup

Vector and tensor analyzing powers of the breakup reaction at 130 and 100 MeV deuteron beam energies have been measured at KVI Groningen with the use of the detection systems covering large fractions of the phase space. The high precision data are compared to the theoretical predictions based on various approaches to describe the three nucleon (3N) system dynamics. Theoretical predictions describe very well the vector analyzing power data, with no need to include any three-nucleon force effects for these observables. The tensor analyzing powers can be also very well reproduced by calculations in most of the studied region, but locally certain discrepancies are observed. At 130 MeV for Axy such discrepancies usually appear, or are enhanced, when model 3N forces (3NFs), TM99 or Urbana IX, are included. Problems of all theoretical approaches with describing Axx and Ayy are limited to very small regions of the phase space, usually characterized with the lowest relative energies of the two protons. Predicted effects of 3NFs are much lower at 100 MeV, therefore at this energy equally good consistency between the data and the calculations is obtained with or without 3NFs.

Vector and Tensor Analyzing Powers in Deuteron–Proton Breakup

High precision data for vector and tensor analyzing powers of the \({^1{\rm {H}}(\vec{\rm{d}},\rm{{pp}})\rm{n}}\) breakup reaction at 130 and 100 MeV deuteron beam energies have been measured in a large fraction of the phase space. They are compared to the theoretical predictions based on various approaches to describe the three nucleon (3N) system dynamics. Theoretical predictions describe very well the vector analyzing power data, with no need to include any three-nucleon force effects for these observables. Tensor analyzing powers can be also very well reproduced by calculations in most of the studied region, but locally certain discrepancies are observed. At 130 MeV for A xy such discrepancies usually appear, or are enhanced, when model 3N forces are included. Predicted effects of 3NFs are much lower at 100 MeV and at this energy equally good consistency between the data and the calculations is obtained with or without 3NFs.

Vector and tensor analyzing powers in deuteron-proton breakup at 130 MeV

High-precision data for vector and tensor analyzing powers for the $^{1}\mathrm{H}$$(\mathrm{dP\vec},\mathit{pp})n$ reaction at a 130-MeV deuteron beam energy have been measured over a large part of the phase space. Theoretical predictions based on various approaches to describe the three nucleon ($3N$) system reproduce very well the vector analyzing power data and no three-nucleon force effect is observed for these observables. Tensor analyzing powers are also very well reproduced by calculations in almost the whole studied region, but locally certain discrepancies are observed. For ${A}_{\mathit{xy}}$ such discrepancies usually appear, or are enhanced, when model $3N$ forces, TM99 or Urbana, are included. Problems of all theoretical approaches with describing ${A}_{\mathit{xx}}$ and ${A}_{\mathit{yy}}$ are limited to very small kinematical regions, usually characterized by the lowest energy of the relative motion of the two protons.

Three-nucleon force and the A(y) puzzle in intermediate energy p--> + d and d--> + p elastic scattering

New vector analyzing-power data on p-->+d elastic scattering at E(p) = 150 and 190 MeV have been measured. These are presented together with existing data and with recent d-->+p vector and tensor analyzing power data at E(d) = 270 MeV. The strong negative extremum of both vector analyzing powers A(p)(y) and A(d)(y) at straight theta(c.m.) approximately 80 degrees -120 degrees is underestimated by Faddeev calculations using modern NN forces. Inclusion of the Tucson-Melbourne 3N force shifts the minima upwards, but with conflicting results for A(p)(y), and leading to a good description for A(d)(y). An A(p)(y) puzzle, previously thought to exist at energies E(N)</=30 MeV only, appears to exist also at intermediate energies.

Determination of the asymptoticD- toS-state ratio for6Livia(6Li→,d)transfer reactions

Measurements of cross section, vector analyzing power ${A}_{y},$ and tensor analyzing powers ${A}_{\mathrm{zz}}$ and ${A}_{\mathrm{xz}}$ over the angular range $10\ifmmode^\circ\else\textdegree\fi{}&lt;~{\ensuremath{\theta}}_{\mathrm{lab}}&lt;~40\ifmmode^\circ\else\textdegree\fi{}$ have been performed at ${E(}^{6}\mathrm{Li})=34 \mathrm{MeV}$ for the ${}^{58}\mathrm{Ni}{(}^{6}\mathrm{Li}\ensuremath{\rightarrow}{,d)}^{62}\mathrm{Zn}$ and ${}^{40}\mathrm{Ca}{(}^{6}\mathrm{Li}\ensuremath{\rightarrow}{,d)}^{44}\mathrm{Ti}$ reactions leading to the ground state and first excited state of both residual nuclei. The reactions are described by distorted-wave Born approximation calculations, assuming a direct $\ensuremath{\alpha}$-particle transfer mechanism. The asymptotic $D/S$ state ratio $\ensuremath{\eta}$ for the $d+\ensuremath{\alpha}$ relative wave function in ${}^{6}\mathrm{Li}$ is determined. In this one-step analysis, the best fit to the tensor observables leads to a value of $\ensuremath{\eta}=+0.0003\ifmmode\pm\else\textpm\fi{}0.0009.$ This value is in disagreement with most of the previous theoretical and empirical determinations of $\ensuremath{\eta}.$ An investigation of two-step reaction mechanisms is performed, allowing the ${J}^{\ensuremath{\pi}}{=3}^{+},$ ${2}^{+},$ and ${1}^{+}$ states in ${}^{6}\mathrm{Li}$ to contribute to the transfer reaction channel. Reasonable agreement is achieved with the cross section and vector analyzing power data for several possible two-step amplitudes. It is found that the fitted magnitude of $\ensuremath{\eta}$ increases with increasing two-step amplitude, giving $\ensuremath{\eta}=\ensuremath{-}0.0030\ifmmode\pm\else\textpm\fi{}0.0022$ for unit amplitude, therefore not changing significantly from our one-step result.

Deformation Effects inL6i

The asymptotic $D$- to $S$-state ratio $\ensuremath{\eta}$ for the $〈d\ensuremath{\alpha}|{}^{6}\mathrm{Li}〉$ bound-state overlap is determined from measurements of the tensor analyzing powers for ( ${}^{6}\stackrel{\ensuremath{\rightarrow}}{\mathrm{Li}},d$) reactions on medium-heavy targets. The reactions are described by the distorted-wave Born approximation assuming a direct $\ensuremath{\alpha}$-particle transfer reaction mechanism. The calculations provide good agreement with cross section and vector analyzing power data. A best fit to the tensor analyzing power data results in a new value of $\ensuremath{\eta}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}+0.0003\ifmmode\pm\else\textpm\fi{}0.0009$, much smaller than previous experimental and theoretical determinations.

Adiabatic treatment of final states in (p,d*) reactions.

The (p,${\mathit{d}}^{\mathrm{*}}$) pickup reaction, leading to spin-singlet and spin-triplet continuum final states of the np system, is treated within the adiabatic approximation. Calculations are carried out for the $^{13}\mathrm{C}$(p,${\mathit{d}}^{\mathrm{*}}$) and $^{13}\mathrm{C}$(p,d) reactions at 35 MeV, leading to the ground and 4.44 MeV states of $^{12}\mathrm{C}$, for which new data have recently been reported. The np relative energy dependence of the (p,${\mathit{d}}^{\mathrm{*}}$) cross sections and the contributions from triplet and singlet configurations are clarified. We show that, within the adiabatic model, theoretical expectations for the magnitude of the singlet state cross section and of the relative magnitudes of the cross sections for the (p,d) and singlet and triplet (p,${\mathit{d}}^{\mathrm{*}}$) channels are particularly transparent. The calculated adiabatic model cross sections differ by an order of magnitude from recently published calculations and data. We show that vector analyzing power data for the ground state transition could be very valuable in clarifying this disagreement. \textcopyright{} 1996 The American Physical Society.

Angular momentum dependent absorption in 6Li scattering.

Measurements are reported for (a) 50 MeV $^{6}\mathrm{Li}$${+}^{12}$C elastic and inelastic scattering to the ${2}^{+}$ (4.44 MeV), ${0}^{+}$ (7.65 MeV), and ${3}^{\mathrm{\ensuremath{-}}}$ (9.64 MeV) states in $^{12}\mathrm{C}$, (b) 20 MeV $^{6}\mathrm{Li}$${+}^{12}$C elastic scattering, (c) 50 MeV $^{6}\mathrm{Li}$${+}^{16}$O elastic and inelastic scattering to the unresolved ${0}^{+}$/${3}^{\mathrm{\ensuremath{-}}}$ (6.05/6.13 MeV) and ${2}^{+}$/${1}^{\mathrm{\ensuremath{-}}}$ (6.92/7.12 MeV) states in $^{16}\mathrm{O}$, and (d) 50 MeV $^{6}\mathrm{Li}$${+}^{9}$Be elastic and inelastic scattering to the 5/${2}^{\mathrm{\ensuremath{-}}}$ (2.43 MeV) state in $^{9}\mathrm{Be}$. Data were measured out to approximately 100${\mathrm{\ifmmode^\circ\else\textdegree\fi{}}}_{\mathrm{c}.\mathrm{m}.}$. A mid-angle plateau characteristic of $^{6}\mathrm{Li}$ scattering in the 5--10 MeV/nucleon energy range is confirmed in the $^{12}\mathrm{C}$ and $^{16}\mathrm{O}$ scattering but is not so apparent in the $^{9}\mathrm{Be}$ scattering.Two energy-dependent, six-parameter optical model potentials, both of which describe $^{6}\mathrm{Li}$${+}^{12}$C elastic scattering at $^{6}\mathrm{Li}$ bombarding energies of 11, 20, 24, 30, 50, 60, 99, 156, and 210 MeV through the forward angle region before the plateau, are coupled with an angular momentum dependent imaginary potential. The results show improved descriptions of the plateau region and back angle scattering and a better description of 30 MeV $^{6}\mathrm{Li}$${+}^{12}$C vector analyzing power data than has previously been published. The $^{6}\mathrm{Li}$${+}^{12}$C inelastic scattering data are described by distorted-wave-Born-approximation calculations. Results of a double folded analysis of $^{6}\mathrm{Li}$${+}^{12}$C elastic scattering at the above energies show a systematic variation of the double folded normalization, N, and the imaginary volume integral. $^{6}\mathrm{Li}$${+}^{16}$O, $^{9}\mathrm{Be}$ elastic scattering data are analyzed with optical model and double folded potentials and the inelastic scattering data are described with distorted-wave-Born-approximation calculations.

Spin-one Kemmer-Duffin-Petiau equations and intermediate-energy deuteron-nucleus scattering.

We present a description of the spin-one Kemmer-Duffin-Petiau equations. An effective second-order equation is obtained for various types of interactions. An argument is given for the use of one particular form of interaction for deuteron-nucleus scattering. This provides the basis for a generalization of the standard Watanabe model in which Dirac scalar and vector nucleon-nucleus potentials are used as input. Parameter-free calculations are performed using both phenomenological and microscopic nucleon-nucleus potentials, and results are compared with deuteron-nucleus elastic scattering data at 400 and 700 MeV. Qualitative agreement is generally obtained. A good description of the forward-angle vector analyzing power data is achieved.

The energy dependence of polarization observables in the 2H(d, γ) 4He reaction

Measurements of the tensor and vector analyzing powers, A yy (130°) and A y (130°), have been obtained for the 2H(d, γ ) 4He reaction for energies ranging from E d(lab) = 0.3 MeV to E d(lab) = 50 MeV. The A yy (130°) data are sensitive to the D-state present in the ground state of 4He and are observed to have their maximum value near E d = 30 MeV. The vector analyzing power data show a maximum near E d = 3 MeV. The data are compared to the results of a microscopic multi-channel resonating group model calculation.

Two-body forces and amplitudes in the three-body model for the4He( $$\vec d$$ ,pα)n reaction withE d =12 and 17 MeV

The4He(\(\vec d\),pα)n cross section, vector and tensor analyzing-power data with 12 and 17 MeV deuterons at kinematic conditions including proton-alpha quasifree scattering, neutron-alpha and proton-alpha final-state interactions, as well as collinearity, are compared with the predictions of the three-body model using different nucleon-alpha and neutron-proton forces. In general, better two-body potentials give a better fit to the data, except for the vector analyzing-power data. The roles of the impulse and multiple-scattering amplitudes are studied to understand the sensitivity to two-body potentials and to understand the reason for the successes and the failures of the model.

Spin-orbit potentials for elastic scattering of polarized 6Li ions from 12C and 58Ni

Angular distributions of the differential cross section σ/σ R, of the vector analyzing power iT 11 and of the 2nd rank tensor analyzing power T T 20 have been measured for elastic scattering of 6Li from 12C and 58Ni at 19.2 and 20.0 MeV, respectively. The vector and tensor polarization data can be well described using in addition to the complex central potential a real spin-orbit potential. Best-fit potentials are compared with those from folding models. In addition, vector analyzing power data were measured for 6Li- 12C elastic scattering at 9.0 MeV bombarding energy. They are compared to predictions derived from an analysis of previously measured tensor analyzing powers of the same system at the same energy.

Cluster folding model for polarized 7Li elastic scattering

The vector analysing power data for the elastic scattering of vector polarized 7Li ions in the energy range of 14 to 21 MeV can be fitted by a phenomenological deformed spin-orbit potential, introduced because of the strong deformation of 7Li. Theoretically, a parameter-free cluster folding model including tensor interactions to all ranks is shown to account for the polarization observables for 7 Li + 58Ni scattering.

2.217 MeV state inAr37

Cross section and vector analyzing power data for the 2.217 MeV state in $^{37}\mathrm{Ar}$ have been measured via the ($d,p$) reaction at an incident deuteron energy of 11 MeV. Distorted wave Born approximation analysis of the data establishes the spin parity of this relatively weak state as 7/${2}^{+}$. The data are fairly well reproduced by the calculations indicating that the one-step process plays a dominant role in populating the state in the ($d,p$) reaction. The spectroscopic factor for the state is found to be 0.04\ifmmode\pm\else\textpm\fi{}0.01. Model calculations indicate that two-step and compound nuclear processes have negligible effects on the conclusions.[NUCLEAR REACTIONS $^{36}\mathrm{Ar}(\stackrel{\ensuremath{\rightarrow}}{d},p)$, $E=11.0$ MeV; measured $\ensuremath{\sigma}(\ensuremath{\theta})$, $i{T}_{11}(\ensuremath{\theta})$. Deduced $J$, $\ensuremath{\pi}$, $S$. DWBA analysis.]

A study of the 68Zn(d,p) 69Zn reaction with vector polarized deuterons

Cross sections and vector analyzing powers have been measured for the 68Zn( d , p) 69Zn reaction at E d = 10 MeV. Transitions with l = 0,1,2,3 and 4 were observed. The data were compared to DWBA calculations to make spin and parity assignments and to extract spectroscopic factors. These calculations reasonably reproduced both cross section and vector analyzing power data over most of the angular range. One tentative and five new definitive spin assignments were made on the basis of the present data; ten spin assignments have been confirmed.

The [formula omitted] and [formula omitted] reactions: J-transfer determination and isospin mixing in 12C

Use of the 13C(d, t) 12C and 13C(d, 3He) 12B reactions to study the isospin mixing of the 12.71 and 15.11 MeV levels in 12C has depended upon the prediction by Cohen and Kurath that the j = 1 2 transfer to these 1 + states is negligible compared to they j = 3 2 transfer. In this paper evidence from vector analyzing power data for these reactions obtained at 29 MeV is presented. It is concluded that the j = 1 2 component is small but may not be insignificant and contributes approximately 8% of the total yield to these states. Including a j = 1 2 component of this size in the analysis of this data yields a charge dependent matrix element of 0.12 ± 0.03 MeV as compared to a value of 0.14 ± 0.04 MeV obtained if the j = 1 2 component is excluded. Both of these values are smaller than those reported in previous measurements, and are thus closer to the values resulting from the Coulomb interaction alone. While these results do not refute the evidence presented for the presence of charge dependent nuclear forces, the confidence in their presence is reduced.