E.J. Stephenson

Elastic proton-deuteron scattering at intermediate energies

Observables in elastic proton-deuteron scattering are sensitive probes of the nucleon-nucleon interaction and three-nucleon force effects. The present experimental database for this reaction is large, but contains a large discrepancy between data sets for the differential cross section taken at 135 MeV/nucleon by two experimental research groups. This article reviews the background of this problem and presents new data taken at Kernfysisch Versneller Instituute (KVI). Differential cross sections and analyzing powers for the

The STAR endcap electromagnetic calorimeter

{}^{2}\mathrm{H}(\stackrel{\ensuremath{\rightarrow}}{p},d)p

Features of the analyzing powers in deuteron elastic scattering near 80 MeV

and

Measurement of the analyzing power A[N] in pp elastic scattering in the CNI region with a polarized atomic hydrogen gas jet target

{}^{1}\mathrm{H}(\stackrel{\ensuremath{\rightarrow}}{d},d)p

NON-SPIN-FLIP (HE-3, T) CHARGE-EXCHANGE AND ISOBARIC ANALOG STATES OF ACTINIDE NUCLEI STUDIED AT THETA=0-DEGREES, E(HE-3)=76 MEV AND 200 MEV

reactions at 135 MeV/nucleon and 65 MeV/nucleon, respectively, have been measured. The differential cross-section data differ significantly from previous measurements and consistently follow the energy dependence as expected from an interpolation of published data taken over a large range at intermediate energies.

Resonance states in 22Mg for reaction rates in the rp-process

The STAR endcap electromagnetic calorimeter will provide full azimuthal coverage for high-pT photons, electrons and electromagnetically decaying mesons over the pseudorapidity range 1.086⩽η⩽2.00. It includes a scintillating-strip shower-maximum detector to provide π0/γ discrimination and preshower and postshower layers to aid in distinguishing between electrons and charged hadrons. The triggering capabilities and coverage it offers are crucial for much of the spin physics program to be carried out in polarized proton–proton collisions.

An in-beam polarimeter for intermediate energy protons using p + d elastic scattering

Abstract Measurements of the differential cross section and vector ( A y ) and tensor ( A yy ) analyzing powers are reported for deuteron elastic scattering on 58 Ni at 80 MeV. A smooth exponential decline in the cross section is present at large scattering angles. Both A y and A yy rise to large, positive values beyond 60°. These effects are understood in terms of a semiclassical description of the scattering involving only the real central and spin-orbit potentials. A comparison is made to optical-model calculations using global potentials. Additional calculations show that the T R and T P tensor potentials have small but distinguishable effects on the tensor analyzing powers.

Deeply-bound hole states in 57Co and the spreading of the 1d52 hole strength distribution

The analyzing power AN for pp elastic scattering is expected to reach a peak value of 0.045 in the Coulomb Nuclear Interference (CNI) region at a momentum transfer −t of 0.003 (GeV/c). During the 2004 RHIC Run, we completed a measurement of AN in the CNI region by detecting the recoil protons from pp elastic scattering using a polarized atomic hydrogen gas jet target and the 100 GeV RHIC proton beam. We report the first measurements of the AN absolute value and shape in the −t range from 0.0015 to 0.010 (GeV/c) with a precision better than 0.005 for each AN data point. The recoil protons were detected with two arrays of Si detectors. The absolute target polarization as monitored by a Breit-Rabi polarimeter was stable at 0.924±0.018. This result allows us to further investigate the spin dependence of elastic pp scattering in the very low −t region.

The precision of angular extrapolation for determining the deuteron asymptotic D- to S-state ratio

The (He-3, t) charge-exchange reaction has been studied at theta = 0-degree-C and bombarding energies of E(He-3) = 76.5 MeV and 200 MeV. Spectra were measured using magnetic analysis for target nuclei of C-12, C-13, O-16, F-19, Si-28, Si-29, Si-30, Zr-90, Sn-117, Sn-120, (nat)Ta, (nat)W, Au-197, Pb-208, Th-230, Th-232, U-234, U-236, U-238 and Pu-244. The measurements at 76.5 MeV concentrated on the isobaric analog states of several actinide nuclei, particularly on their widths and the branching ratios for proton decay. Cross sections, Q-values and total widths were determined for the transitions to the isobaric analog states. Coulomb displacement energies derived from the measured Q-values display the influence of deformed nuclear shapes. Escape widths GAMMA-up and spreding widths GAMMA-down of the isobaric analog states in five actinide nuclei were deduced from the measured proton-decay branching ratios. They were found to be in agreement with predictions which postulate isospin mixing via the Coulomb force with the (T0-1)-component of the isovector giant monopole resonance. The measurements at 200 MeV were concerned with transitions to isobaric analog states in both light and heavy nuclei, including several actinide nuclei, but Gamow-Teller resonances and transitions to numerous other states were also observed. The measured cross sections for several transitions to isobaric analog states from Si-30 to Pb-208 were used to extract the effective interaction V(tau) for non-spin-flip (He-3, t) charge exchange at E(He-3) almost-equal-to 200 MeV. The interaction strength V(tau) decreases by a factor 0.6 when compared to previously measured values for the energy range E(He-3) = 65 to 90 MeV. An angular distribution from theta(t) = 0-degree to 16-degrees for the transition to the isobaric analog state in Sb-120 measured at E(He-3) = 200 MeV was found to be in very good agreement with microscopic calculations.

Deuteron elastic scattering in the large angular momentum limit

Abstract Motivated by the need of spectroscopic data to better understand the astrophysical rp-process, we developed a new experimental method using the Grand Raiden magnet spectrometer to study protin rich nuclei with α and 3 He induced reactions. First results of the 24 Mg( 4 He, 6 He) 22 Mg reaction at 206 MeV and 0° are presented, showing states relevant for resonant reaction rate calculations of the proton capture 21 Na(p,γ) 22 Mg and the 18 Ne(α,p) 21 Na reaction which controls the break-out of the hot CNO cycles at X-ray burst conditions.