W. Haeberli

Elastic scattering of 9–13 MeV vector polarized deuterons☆

Abstract Angular distributions of the cross section and vector analyzing power were measured for elastic scattering of 9, 11 and 13 MeV deuterons from 27Al, Si, 46Ti, 48Ti, 53Cr, 68Zn, 90Zr and 120Sn. The results were analyzed with the optical model. The analysis also included results from similar previous experiments on 18 nuclides for deuteron energies between 5 and 12.3 MeV. Good agreement with most of the measurements was obtained by adjusting only the parameters of the absorptive part of the potential from one nucleus to the next. All other parameters were held constant, except for the real potential depth which was assumed to depend on Z/A 1 3 . The volume integral of the imaginary potential seems to be correlated with the deformation parameter.

-Measurement of the proton's electric to magnetic form factor ratio from 1H(over -->)(e(over -->),e'p).

We report the first precision measurement of the proton electric to magnetic form factor ratio from spin-dependent elastic scattering of longitudinally polarized electrons from a polarized hydrogen internal gas target. The measurement was performed at the MIT-Bates South Hall Ring over a range of four-momentum transfer squared Q2 from 0.15 to 0.65 (GeV/c)(2). Significantly improved results on the proton electric and magnetic form factors are obtained in combination with existing cross-section data on elastic electron-proton scattering in the same Q2 region.

Measurement of the proton's electric to magnetic form factor ratio from H→1(e→,e′p)

We report the first precision measurement of the proton electric to magnetic form factor ratio from spin-dependent elastic scattering of longitudinally polarized electrons from a polarized hydrogen internal gas target. The measurement was performed at the MIT-Bates South Hall Ring over a range of four-momentum transfer squared Q2 from 0.15 to 0.65 (GeV/c)(2). Significantly improved results on the proton electric and magnetic form factors are obtained in combination with existing cross-section data on elastic electron-proton scattering in the same Q2 region.

Study of the reactions 118Sn(d, t) and 98Mo(d, t): (I). Spectroscopy of 117Sn and 97Mo

Abstract The vector analyzing power and differential cross section have been measured at a deuteron energy of 12.0 MeV for 118 Sn ( d , t ) transitions to six states of 117Sn (Ex = 0.0, 0.16, 0.31, 0.71, 1.02 and 1.18 MeV), for 98 Mo ( d , t ) transitions to eight states of 97Mo (Ex = 0.0, 0.68, 0.72, 0.89, 1.12, 1.28, 2.39 and 2.52 MeV), and for 118 Sn ( d , d ) and 98 Mo ( d , d ) . Deuteron optical model potentials were obtained from analysis of the elastic scattering measurements, and were used in a DWBA analysis of the ( d , t ) results. Comparison of the measurements and DWBA predictions for σ(θ) and for iT11(θ) allows unambiguous determination of tln and jn for all 118Sn(d, t) and most 98Mo(d, t) transitions. Differences in the triton energy relative to the Coulomb barrier cause marked qualitative differences in the measured cross sections and analyzing powers between 118 Sn ( d , t ) and 98 Mo ( d , t ) transitions of the same ln and jn.

The FILTEX / HERMES polarized hydrogen atomic beam source

The FILTEX/HERMES atomic beam source (ABS) for polarized hydrogen is described. Recent improvements concern mainly the optimization of the beam forming system and a new design of the sextupole magnet system. For a precise measurement (error 5%) of the output flow a calibrated compression tube was installed. The output flow of 0.81×1017 H atoms per second in two hyperfine substates was constant within 2% in a long-term measurement over 16 h. At the FILTEX test experiment, the target density in the storage cell fed by the ABS was constant within the experimental error of 4% over a period of four months.

Analyzing powers and spin correlation coefficients for p+d elastic scattering at 135 and 200 MeV

The proton and deuteron analyzing powers and ten of the possible 12 spin correlation coefficients have been measured for p+d elastic scattering at proton bombarding energies of 135 and 200 MeV. The results are compared with Faddeev calculations using two different NN potentials. The qualitative features of the extensive data set on the spin dependence in p+d elastic scattering over a wide range of angles presented here are remarkably well explained by two-nucleon force predictions without inclusion of a three-nucleon force. The remaining discrepancies are, in general, not alleviated when theoretical three-nucleon forces are included in the calculations.

The optical model for elastic scattering of 10 to 15 MeV polarized deuterons from medium-weight nuclei☆

Abstract Differential cross sections and all four analysing powers have been measured for deuteron elastic scattering from 46Ti, 52Cr, 54Fe, 68Zn and 90Zr at Ed = 10.0 MeV, 68Zn and 90Zr at 12.0 MeV, and 46Ti and 54Fe at 13.0 MeV. These data, and other data from the literature for deuteron scattering from 52Cr, 56Fe, 60Ni, 90Zr and 122Sn at Ed = 15 MeV, were analyzed in terms of an optical potential containing central, spin-orbit ( L · s ) and tensor (Tr terms, all of which are complex. All of the data were adequately reproduced by the calculations, except for the tensor analysing powers for the N = 28 nuclei 52Cr and 54Fe. The best-fit L · s potentials have very small diffusenesses, and the real part of the Tr tensor potential is found to be much smaller than the imaginary part. There is some evidence that the Woods-Saxon potential shape is inadequate to describe the real central potentials for deuteron energies more than 8 or 9 MeV above the Coulomb barrier.

Study of the reactions 208Pb(d, p) and 208Pb(d, t) near the coulomb barrier

Abstract The vector analyzing power and differential cross section have been measured at a deuteron energy of 12.3 MeV for 208 Pb ( d , p ) , transitions to seven states of 209 Pb ( E x = 0.0, 0.79, 1.42, 1.56, 2.01 and 2.47+2.51 MeV, for 208 Pb ( d , t ) transitions to three states 207 Pb ( E x = 0.0, 0.57 and 0.89 MeV), and for 208 Pb ( d , d ) . Two deuteron optical model potentials were obtained from analysis of the elastic scattering measurements, and were used in a DWBA analysis of the present transfer-reaction results and of previous results for 207 Pb ( d , p 0 ) 208 Pb . The sensitivity of the DWBA analysis to the nuclear interior is investigated. The relative importance of Coulomb and of nuclear distortions is discussed. The sign of the vector analyzing power for given l n depends on j n and on Q -value for both the ( d, p ) and the ( d,t ) reactions. The Q -dependence invalidates the simple rule proposed by Griffith and Roman to relate j n to the predominant sign of iT 11 . Comparison of the measurements and DWBA predictions for iT 11 ( θ ) allows unambiguous determination of j n for all transitions except 207 Pb ( d , p 0 ) . All spins determined in the present work confirm previous assignments. The vector analyzing powers for the 208 Pb ( d , t 0 ) 207 Pb and 207 Pb ( d , p 0 ) 208 Pb transitions are observed to be similar in angular dependence but opposite in sign at all angles. The sign reversal reflects differences in the distortions of the proton and triton waves.

Search for time-reversal violation in the beta decay of polarized 8Li nuclei.

The transverse polarization of electrons emitted in the beta decay of polarized 8Li nuclei has been measured. For the time-reversal violating triple correlation parameter we find R=(0.9+/-2.2)x10(-3). This result is in agreement with the standard model and yields improved constraints on exotic tensor contributions to the weak interaction. Combined with other experimental results and using a model for the coupling constants, a new limit for the mass of a possible scalar leptoquark, m(LQ)>560 GeV/c(2) (90% C.L.), is obtained.

Polarization measurement for polarized gas targets

Abstract Recently proposed experiments with polarized gas targets in storage rings require methods to measure the target polarization to an accuracy of a few percent or better. The task is made more difficult because the target atoms are injected into a long, narrow target cell to increase the target thickness available from atomic beam sources or optically pumped sources. Here we propose to extract ions formed in the cell by the charged particle beam, and to measure their polarization by nuclear or atomic methods. The advantage of this method is that the average target polarization is determined independent of possible spatial variations of target polarization. The proposed method was applied to a deuterium gas target, whose tensor polarization was measured by means of the 3 H(d, n) 4 He reaction. We show that uniform ion extraction can be achieved for a cell with a length-to-diameter ratio of 30. We find that the deuterons in molecules formed by recombination of polarized deuterium atoms are almost completely depolarized. Thus target polarization measurements must include measurements on molecules as well as atoms. We discuss nuclear reactions suitable to measure the polarization of H and D targets, as well as atomic methods to measure the polarization of the extracted ions.