Deuteron Tensor Research Articles

Coherent pion production in proton–deuteron collisions

Values of the proton analysing power in the $pd\to{}^{3}\textrm{He}\,\pi^0/^{3}\textrm{H}\,\pi^+$ reactions at 350-360~MeV per nucleon were obtained by using a polarised proton beam incident on a deuterium cluster-jet target and with a polarised deuteron beam incident on a target cell filled with polarised hydrogen. These results have a much larger angular coverage than existing data. First measurements are also presented of the deuteron vector analysing power and the deuteron-proton spin correlations. Data were also obtained on the deuteron-proton spin correlation and proton analysing power at small angles at 600~MeV per nucleon, though the angular coverage at this energy was much more restricted even when using a deuteron beam. By combining the extrapolated values of the spin correlations to the forward or backward directions with published measurements of the deuteron tensor analysing powers, the relative phases between the two non-vanishing amplitudes were evaluated.

Study of coherent pion production in proton-deuteron collisions with polarized beams and target at ANKE-COSY

Values of the proton analysing power, deuteron vector analysing power, and the deuteron-proton spin correlations in the pd → 3 He π 0 / 3 H π + reactions at 350-360 MeV per nucleon were obtained by using polarized beams and target at ANKE-COSY. Data were also obtained on the deuteron-proton spin correlation and proton analysing power at small angles at 600 MeV per nucleon. By combining the extrapolated values of the spin correlations to the forward or backward directions with published measurements of the deuteron tensor analysing powers, the relative phases between the two non-vanishing amplitudes were evaluated.

The Deuteron Polarized Tensor Structure Function b1

We describe Jefferson Lab E12-13-011, an inclusive deep inelastic scattering experiment to measure the leading twist deuteron tensor structure function b1 in the region 0.16 < x < 0.49 for 0.8 < Q2 < 5.0 GeV2. The experiment has been conditionally approved, contingent on target performance, with A− physics rating to run with 30 days of 11 GeV incident beam on a tensor polarized solid target in Jefferson Lab's Hall C.

Investigation into tensor polarization enhancement of solid polarized targets

A discussion of tensor polarization of solid targets produced by Dynamic Nuclear Polarization and Dynamic Nuclear Orientation in the use of nuclear physics experiments is presented. Techniques in the deuteron tensor polarization enhancement and enhanced tensor polarization measurement uncertainty are also discussed in the interest and preparation of future experiments.

Absence of spin dependence in the final state interaction of the [formula omitted] reaction

The deuteron tensor analysing power T20 of the d→p→He3η reaction has been measured at the COSY-ANKE facility in small steps in excess energy Q up to Q=11 MeV. Despite the square of the production amplitude varying by over a factor of five through this range, T20 shows little energy dependence. This is evidence that the final state interaction causing the energy variation is not influenced by the spin configuration in the entrance channel. The weak angular dependence observed for T20 provides useful insight into the amplitude structure near threshold.

Excitation of the [formula omitted] isobar in deuteron charge exchange on hydrogen at 1.6, 1.8, and 2.3 GeV

The charge-exchange break-up of polarised deuterons d→p→{pp}sn, where the final {pp}s diproton system has a very low excitation energy and hence is mainly in the S01 state, is a powerful tool to probe the spin-flip terms in the proton–neutron charge-exchange scattering. Recent measurements with the ANKE spectrometer at the COSY storage ring at 1.6, 1.8, and 2.27 GeV have extended these studies into the pion-production regime in order to investigate the mechanism for the excitation of the Δ(1232) isobar in the d→p→{pp}sX reaction. Values of the differential cross section and two deuteron tensor analysing powers, Axx and Ayy, have been extracted as functions of the momentum transfer to the diproton or the invariant mass MX of the unobserved system X. The unpolarised cross section in the high MX region is well described in a model that includes only direct excitation of the Δ isobar through undistorted one pion exchange. However, the cross section is grossly underestimated for low MX, even when Δ excitation in the projectile deuteron is included in the calculation. Furthermore, direct Δ production through one pion exchange only reproduces the angular dependence of the difference between the two tensor analysing powers.

The neutron-proton charge-exchange amplitudes measured in the dp → ppn reaction

The unpolarised differential cross section and the two deuteron tensor analysing powers A_{xx} and A_{yy} of the pol{d}p -> (pp)n charge-exchange reaction have been measured with the ANKE spectrometer at the COSY storage ring. Using deuteron beams with energies 1.2, 1.6, 1.8, and 2.27 GeV, data were obtained for small momentum transfers to a (pp) system with low excitation energy. The results at the three lower energies are consistent with impulse approximation predictions based upon the current knowledge of the neutron-proton amplitudes. However, at 2.27GeV, where these amplitudes are far more uncertain, agreement requires a reduction in the overall double-spin-flip contribution, with an especially significant effect in the longitudinal direction. These conclusions are supported by measurements of the deuteron-proton spin-correlation parameters C_{x,x} and C_{y,y} that were carried out in the pol{d}pol{p} -> (pp)n reaction at 1.2 and 2.27GeV. The values obtained for the proton analysing power also suggest the need for a radical re-evaluation of the neutron-proton elastic scattering amplitudes at the higher energy. It is therefore clear that such measurements can provide a valuable addition to the neutron-proton database in the charge-exchange region.

Precise Measurement of Deuteron Tensor Analyzing Powers with BLAST

We report a precision measurement of the deuteron tensor analyzing powers T(20) and T(21) at the MIT-Bates Linear Accelerator Center. Data were collected simultaneously over a momentum transfer range Q=2.15-4.50 fm(-1) with the Bates Large Acceptance Spectrometer Toroid using a highly polarized deuterium internal gas target. The data are in excellent agreement with calculations in a framework of effective field theory. The deuteron charge monopole and quadrupole form factors G(C) and G(Q) were separated with improved precision, and the location of the first node of G(C) was confirmed at Q=4.19±0.05 fm(-1). The new data provide a strong constraint on theoretical models in a momentum transfer range covering the minimum of T(20) and the first node of G(C).

On the possibility to measure the imaginary part of the spin-dependent amplitude of zero-angle coherent elastic scattering in a spin-filter experiment with an unpolarized proton beam interacting with a polarized deuterium target

As deuterons pass through an unpolarized target, there appear the phenomena of spin rotation (oscillation) and spin dichroism of deuterons; both phenomena are the manifestation of the deuteron birefringence effect. The magnitude of the effect is determined by the refractive index of deuterons in matter, which depends on the spin-dependent part d1 of the amplitude of zero-angle coherent elastic scattering of the deuteron by the nucleus. Spin dichroism is determined by the imaginary part of this amplitude, and in view of the optical theorem, by the total scattering cross-section, which is different for different spin states of the deuteron. The phenomenon of spin dichroism of deuterons results in the fact that after passing through the target, the initially unpolarized deuteron beam acquires tensor polarization proportional to the difference in the total cross-sections of scattering of deuterons with different spin states by the nucleus. The stated difference was first measured for deuterons with energies up to 20 MeV, where the phenomenon of deuteron spin dichroism was experimentally revealed, and the deuteron tensor polarization was measured. The phenomenon of spin dichroism, i.e., the production of tensor polarization was also observed at high deuteron energy. In the present report we discuss the possibility that the imaginary part of the amplitude d1 of deuteron scattering by the proton may be determined experimentally by measuring the rate of the decrease in the intensity of an unpolarized proton beam in a storage ring as the beam passes through a tensor-polarized deuterium target.

EXPERIMENTS ON THE STUDY OF DEUTERON-PROTON INTERACTION AT INTERNAL TARGET AT NUCLOTRON

The experimental program on the study of deuteron-proton interaction at Internal Target at Nuclotron is discussed. Recent results on the deuteron vector and tensor analyzing powers in dp -elastic scattering obtained at intermediate energies are presented. The status of the DSS setup upgrade is reported.

Tensor electric polarizability of the deuteron in storage-ring experiments

The tensor electric polarizability of the deuteron gives important information about spin-dependent nuclear forces. If a resonant horizontal electric field acts on a deuteron beam circulating into a storage ring, the tensor electric polarizability stimulates the buildup of the vertical polarization of the deuteron (the Baryshevsky effect). General formulas describing this effect have been derived. Calculated formulas agree with the earlier obtained results. The problem of the influence of tensor electric polarizability on spin dynamics in such a deuteron electric-dipole-moment experiment in storage rings has been investigated. Doubling the resonant frequency used in this experiment dramatically amplifies the Baryshevsky effect and provides the opportunity to make high-precision measurements of the deuteron's tensor electric polarizability.

Deuteron tensor polarization componentT20(Q2)as a crucial test for deuteron wave functions

The deuteron tensor polarization component ${T}_{20}({Q}^{2})$ is calculated by the relativistic Hamiltonian dynamics approach. It is shown that in the range of momentum transfers available with current experiments, relativistic effects, meson exchange currents, and the choice of nucleon electromagnetic form factors almost do not influence the value of ${T}_{20}({Q}^{2})$. However, this value depends strongly on the actual form of the deuteron wave function, that is, on the model of the $\mathit{NN}$ interaction in the deuteron. So the existing data for ${T}_{20}({Q}^{2})$ provide a crucial test for deuteron wave functions.

Charge-exchange reaction pd → n(pp) within the Bethe-Salpeter approach

The charge-exchange reaction pd → n(pp) at low momentum transfers and low excitation energies of the pp pair is considered within the Bethe-Salpeter approach. The method is proposed for calculating observables in the case where the pp pair is in the 1 S 0 state. The results of methodological numerical calculations for the differential cross sections and the tensor analyzing power T 20 are presented. The possibility of using the reaction in question as a basic reaction for creating a deuteron tensor polarimeter at high energies and for obtaining additional information about the elementary amplitude for nucleon-nucleon charge-exchange is predicted.

Deuteron form factors for the Nijmegen potentials

The deuteron form factors and tensor polarizations in elastic ed scattering are considered for four versions of the Nijmegen nucleon-nucleon potentials. The numerical deuteron wave functions in these potentials are approximated by a series of Gaussian functions with the result that it can be used in any computations of integrated characteristics. The quality of this approximation of the wave function is exemplified by comparing the results that it produces for the momentum distributions, the quadrupole moment, the D-state probability, and the deuteron radius with the results of the corresponding precise calculations.

Study of the ABC enhancement in the [formula omitted] reaction

The d d→α X 0 reaction at beam energies close to the η threshold shows very strong structure in the missing mass corresponding to the ABC enhancement. The deuteron tensor analysing power A yy , and the slope of the vector analysing power A y with respect to angle, have been measured for this reaction around the forward direction. Both signals are small, and their variations with the α-particle momentum are in broad agreement with a theoretical model in which each pair of nucleons in the projectile and target deuterons undergoes pion production through the NN→ dπ reaction.

Spin observables for thepd↔π+treaction around theΔresonance

The proton analyzing power ${A}_{y0}$ and the deuteron tensor analyzing power ${T}_{20}$ are evaluated for the $\mathrm{pd}\ensuremath{\leftrightarrow}{\ensuremath{\pi}}^{+}t$ process, in the energy region around and above the $\ensuremath{\Delta}$ resonance. These calculations extend a previous analysis of the excitation function and differential cross section, based on a model embodying one- and two-body $p$-wave absorption mechanisms and isobar excitation. The three-nucleon bound state and the $\mathrm{pd}$ scattering state are evaluated through Faddeev techniques for both the Bonn and Paris potentials. The spin variables exhibit a greater sensitivity to the number of included three-nucleon partial waves than the cross sections, while the role played by the initial- or final-state interactions appears to be small. The results for the tensor analyzing power at backward angles show a non-negligible dependence on the potentials employed, consistently with what has been previously found for the cross sections. The calculation of spin observables gives a clear indication that other reaction mechanisms (presumably $s$-wave two-body absorption) have to be included in the model, in order to reproduce the experimental data below the $\ensuremath{\Delta}$ resonance, in analogy with the simpler $\mathrm{pp}\ensuremath{\leftrightarrow}\ensuremath{\pi}d$ process.

Polarization transfer observables in πd elastic scattering

Polarization transfer observables in π + d elastic scattering have been measured for the first time. Four polarization transfer parameters were determined at pion energies T π =134 MeV and 180 MeV at scattering angles θ π,C.M. between 100° and 140° using a deuteron target polarized perpendicular to the scattering plane and a deuteron tensor polarimeter. The data are compared to different predictions from the SAID phase shift analysis and Faddeev calculations.

Polarization transfer observables in πd elastic scattering

The first measurement of the polarization transfer observables in πd elastic scattering has been performed at two pion bombarding energies below and at the Δ 33 resonance (134 MeV and 180 MeV) using a deuteron target polarized perpendicular to the scattering plane and a deuteron tensor polarimeter.

Determination of the asymptotic D- to S-state ratio for 3He via (d

Angular distributions of the tensor analyzing powers ${A}_{\mathrm{yy}}$ and ${A}_{\mathrm{zz}}$ have been measured for the ground-state transition in the $^{93}\mathrm{Nb}(\stackrel{\ensuremath{\rightarrow}}{d}, ^{3}\mathrm{He})^{92}\mathrm{Zr}$ reaction at ${E}_{d}=12$ MeV, and of ${A}_{\mathrm{zz}}$ for the ground-state transitions in $^{63}\mathrm{Cu}(\stackrel{\ensuremath{\rightarrow}}{d}, ^{3}\mathrm{He})^{62}\mathrm{Ni}$ at ${E}_{d}=8$ MeV and $^{89}\mathrm{Y}(\stackrel{\ensuremath{\rightarrow}}{d}, ^{3}\mathrm{He})^{88}\mathrm{Sr}$ at ${E}_{d}=10.5$ MeV. The data are compared with predictions of full finite-range distorted-wave Born approximation (DWBA) calculations from which the asymptotic $D$- to $S$-state ratio, $\ensuremath{\eta}$, for $^{3}\mathrm{He}$ is extracted to be -0.0386\ifmmode\pm\else\textpm\fi{}0.0045\ifmmode\pm\else\textpm\fi{}0.0012. The difficulties with a choice of deuteron tensor optical potentials used in the DWBA calculations are discussed.

A deuteron tensor polarimeter for low-energy experiments

A deuteron tensor polarimeter utilizing the 3He(d,p) 4He reaction has been calibrated at energies between 113 and 323 keV using implanted 3He targets. It provides an efficient determination of polarization at deuteron energies between 100 and 700 keV due to the presence of the 3 2 + resonance at E d = 430 keV. In an energy range around the resonance the tensor analyzing power A yy = 0.5 at all angles and A zz is −0.85 at a mean angle of 17.5°.