Search

The three polarization tensor components of the deuteron produced in the H( p , d )π + reaction have been measured for the first time. The experiment was performed using a vertically polarized proton beam produced by the SATURNE accelerator. The deuteron polarization was measured with the POLDER polarimeter. The three polarizing powers t2000, t2100 and t2200 and the three spin-transfer observables t2011, t2211 and t2211 have been extracted at a proton kinetic energy of 580 MeV over a wide angular range and at two fixed center-of-mass angles, 132° and 151°, between 800 and 1300 MeV. The six observables, calculated in the C.M. helicity frame, have been compared with predictions of the most refined partial-wave analyses and also with the predictions of a theoretical coupled-channel model which includes the NN-NΔ transition. The comparison between the data and the theory/partial-wave analyses shows some discrepancies which get worse with increasing proton energy. Adding these data to the world database should improve significantly future partial-wave analyses. The Ay0 analyzing power has also been measured over the same kinematical range. The partial-wave analysis predictions are in good agreement with this observable.

During the last decade, our understanding of the πNN system has been improved with the measurement of double polarization observables [1]. In this experiment the recoil deuteron polarization produced in the H ( p , d )π + reaction was measured with the POLDER polarimeter for incident protons of kinetic energies between 580 and 1300 MeV.

Studies of the production of the Δ resonance in hadronic charge exchange reactions show a shift in the Δ peak position. Measurements looking also at the Δ decay products give some evidence for coherent pion production. We have recently completed a new measurement of the 12 C ( p , n ) reaction leading to the Δ resonance, including a higher resolution coincidence measurement of decay π's in the forward direction. We describe the experiment and some aspects of the preliminary analysis.

Fluctuations in the differential cross section and analyzing power for polarized proton scattering from 28Si have been studied over the energy range of 12.0 to 18.0. MeV. States at 0.0 MeV (0+1), 1.78 MeV (2+), 4.61 MeV (4+) and 4.97 MeV (02+) were observed at 140° and 160°. Autocorrelations and cross-correlations were calculated and statistical tests for intermediate structure were carried out. These calculations indicate a coherence width of approximately 50 keV and show no significant evidence for intermediate structure.

Angular distributions of analyzing powers and differential cross sections have been measured for elastic and inelastic scattering of 800 MeV protons from 90 Zr and 92 Zr. The data have been interpreted using both the collective-model distorted-wave Born approximation and the semimicroscopic distorted-wave impulse approximation with the Love and Franey t -matrix. Clear differences in the data for transitions to both the 2 + 1 and the 4 + states in the two nuclei, attributable to differences in the microscopic structures of the states, have been observed. These differences are only partially explained by the semimicroscopic analyses. Interpreting the A y data with the help of recent data-to-data relations suggests that the free L · S interaction used at 800 MeV is incorrect.

We present differential cross sections for p+ d → 3He + π0 at Tp = 300, 350, 400, 425, 450, 470 and 500 MeV, and for p + d → 3H + π+ at 500 MeV, mostly near θπ (c.m.) = 48° and 98°. The ratio dσ(pd → 3H π+)/dσ(pd → 3Heπ0) for identical four momentum transfer at 500 MeV is found to be 2.21 ± 0.17 to 2.57 ± 0.34, depending on angle. The dependence of the invariant matrix element squared |M|2 on the relativistic invariants t and s is examined; for a given value of t, |M|2 is almost independent of s for Tp between 350 and 800 MeV.

In the 54 Fe(p, p'γ) 54 Fe reaction at 10 MeV, angular correlations of gamma rays coincident with protons detected near 180°, have been measured. From an analysis of the angular correlations, unambiguous spin assignments have been made for the 3.345(3), 4.074(3), 4.579(2), 4.781(3), and 4.949(4) MeV states. Model-dependent spin assignments have been made for several other states. The angular correlation analysis also yielded multipole mixing ratios for many transitions and branching ratios for the decay of all states of 54 Fe below 5 MeV. From the same data, an analysis of the Doppler shifts of the coincident gamma rays allowed determination of the lifetimes of the 1.409, 2.959, 3.164, 3.836, 4.048, 4.074, 4.265, 4.287, 4.781 and 4.949 MeV states. Utilizing all the measured quantities, estimates have been of the strengths of 20 E2, 9 M1, and 4 E1 transitions. To aid in understanding the nature of the observed levels, the po- sitions of various n p- m h states have been estimated using a monopole residual interaction. It is found that 2p-4h states as well as lp-3h states may occur at low excitation energies. The 2.540 MeV (O 2 + ) state is probably of the configuration 2p-4h. The decay properties of all states below 3.5 MeV are compared to the predictions of theoretical calculations in which lp-3h proton ( 2 p 3 2 and 1 f 5 2 ) excitations were considered.