A.R. Baldwin

The STAR endcap electromagnetic calorimeter

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.

Large volume neutron detectors with subnanosecond time dispersions

Abstract Design criteria and performance characteristics are described for large-volume (13.1 1 to 118 1) mean-timed plastic-scintillator detectors for neutrons from ≈2 MeV to 2 GeV. Detectors were constructed in six sizes (all 0.102 m thick) from 0.126 m × 1.016 m × 0.102 m to 0.762 m × 1.524 m × 0.102 m. Overall energy resolutions of 230 keV for 80 MeV neutrons, 320 keV for 133 MeV neutrons, and 440 keV for 157 MeV neutrons were achieved in time-of-flight experiments with flight paths of 76, 68, and 91 m, respectively. The detectors have pulse-height responses uniform to ±5% except close to the ends, position resolutions less than 5 cm, and intrinsic time dispersions less than 400 ps. Typical neutron detection efficiencies are 20% for 20 MeV neutrons at a pulse-height threshold of 2 MeV equivalent-electron energy (MeV ee) and 3.5% for 200 MeV neutrons at a pulse-height threshold of 50 MeV ee.

Gamow-Teller and spin-dipole strength in the 40,48Ca(p,n) reactions at 135 MeV

Abstract Spin-flip probabilities for 48Ca( p n )48Sc reveal that at 0° the apparent continuum under and adjacent to the Gamow-Teller giant resonance is also primarily 1+ strength. A comparison of 40Ca[ p n )40Sc and 48Ca( p n )48Sc shows no discernable signature of Gamow-Teller strength in the region −30 > Q(MeV) >−45. The spin-flip component of the dipole resonance for 40Ca is broader than the non-spin-flip component.

A high-performance polarimeter for medium-energy neutrons

Abstract A polarimeter for medium-energy neutrons is described. This polarimeter uses the analyzing power of n–p scattering which is typically +0.50 for laboratory neutron scattering angles near 20° in the energy range from 50 MeV to 1 GeV. Hydrocarbon organic scintillators are employed as “active” scatterers. Calibration data for the analyzing power and the efficiency of the polarimeter are presented.

Electron capture strength for Ni 60 , 62 and Ni 58 , 60 , 62 , 64 ( p , n ) Cu 58 , 60 , 62 , 64 reactions at 134.3 MeV

Background: The strength of electron capture for medium mass nuclei has a significant effect on the evolution of supernovae. There is insufficient knowledge of these strengths and very little data for important radioactive nuclei. Purpose: Determine whether it is feasible to obtain EC strength from studies of T{sub o}+1 excitations in (p, n) reactions, and whether this might yield information for radioactive nuclei. Methods: Cross sections for the {sup 58,60,62,64}Ni(p, n){sup 58,60,62,64}Cu reactions were measured over the angular range of 0.3 deg. to 11.6 deg. at 134.3 MeV using the IUCF neutron time-of-flight facility. Results: The T{sub o}+1 excitations in {sup 60,62}Ni were identified by comparison with inelastic proton scattering spectra, their B(GT) were extracted, and the corresponding electron capture rates in supernovae were calculated. Data from the TRIUMF (n, p) experiments at 198 MeV were reanalyzed; the electron capture rates for the reanalyzed data are in moderately good agreement with the higher resolution (p, n) results, but differ in detail. The possibility of future measurements with radioactive nuclei was considered. Conclusions: It may be possible to obtain low-lying electron capture strength for radioactive nuclei by studying (p, n) reactions in inverse kinematics.

12C(p,n)12N reaction at 135 MeV.

We report observations from the (p,n) reaction on

Measurement of the polarization of a pulsed electron beam with a Møller polarimeter in the coincidence mode

^{12}\mathrm{C}

A comparison of methods for determining neutron detector efficiencies at medium energies

at 135 MeV. The experiment was performed with the beam-swinger neutron time-of-flight system at the Indiana University Cyclotron Facility. Neutrons were detected in large-volume plastic scintillation detectors located in three detector stations at 0\ifmmode^\circ\else\textdegree\fi{}, 24\ifmmode^\circ\else\textdegree\fi{}, and 45\ifmmode^\circ\else\textdegree\fi{} with respect to the undeflected beam line; the flight paths were 91 m, 91 m, and 74 m, respectively. Overall time resolutions of about 825 ps provided energy resolutions of about 350 keV in the first two stations and about 425 keV in the third station. The angular distributions for states with excitation energies up to 10 MeV are presented and comparisons are made with DWIA calculations that use one-body density matrices from 0\ensuremath{\Elzxh}\ensuremath{\omega} and 1\ensuremath{\Elzxh}\ensuremath{\omega} shell-model calculations. New information is deduced on the excitation energies, widths, and spin-parity assignments for several energy levels of

Neutrons from multiplicity-selected La-La and Nb-Nb collisions at 400A MeV and La-La collisions at 250A MeV.

^{12}\mathrm{N}

Neutron spectra at 0° from 83.7‐MeV deuterons and 100.2‐MeV protons on beryllium

. \textcopyright{} 1996 The American Physical Society.