S. J. Freedman

The superconducting neutron decay spectrometer PERKEO

Abstract The superconducting neutron beta-decay spectrometer PERKEO is described. PERKEO is installed at the High Flux Reactor of the Institut Laue-Langevin where it measures beta-decay spectra from a beam of polarized or unpolarized neutrons. It has 4π detection and measurements are made with high count rates at low background. PERKEO has already been used to measure the neutron lifetime and the neutron beta-decay asymmetry. It was also employed in a search for a short-lived axion emitted in neutron capture on protons.

Construction and performance of a large area liquid scintillator cosmic ray anticoincidence detector

Abstract We describe details of the construction and performance of a large area cylindrical cosmic ray anticoincidence detector suitable for a medium energy neutrino experiment. The device provides 4π coverage with approximately 400 m2 of liquid scintillator. Cosmic ray muons are rejected on-line with an inefficiency of ⋍ 10−4 which is improved to a level of ⋍ 3 × 10−6 or less with the application of off-line cuts. We also discuss the custom electronics used to operate and read out the device. Results from studies of the attenuation of neutral cosmic ray backgrounds by passive shielding are included.

A liquid scintillator cosmic ray active shield

Abstract We describe the prototype for an active cosmic ray shield for a neutrino oscillation experiment to be performed at LAMPF. This shield is a large liquid scintillator-filled steel tank viewed by an array of large hemispherical photomultiplier tubes. We discuss the motivation for choosing a liquid scintillation counter and details of its implementation. Results of prototype tests, and tests on liquid scintillator properties, are presented.

Measurement of neutron-decay parameters with PERKEO

Abstract The solenoidal electron spectrometer PERKEO has been used to study the β-decay of the free neutron. We describe measurements of the neutron β-decay asymmetry and the neutron lifetime. The results are A = −0.1146(19) for the asymmetry and τ n = 876(21) s for the lifetime. From these values we determine the weak interaction coupling constants g A and g V .

Solar fusion cross sections. II. Theppchain and CNO cycles

The available data on nuclear fusion cross sections important to energy generation in the Sun and other hydrogen-burning stars and to solar neutrino production are summarized and critically evaluated. Recommended values and uncertainties are provided for key cross sections, and a recommended spectrum is given for {sup 8}B solar neutrinos. Opportunities for further increasing the precision of key rates are also discussed, including new facilities, new experimental techniques, and improvements in theory. This review, which summarizes the conclusions of a workshop held at the Institute for Nuclear Theory, Seattle, in January 2009, is intended as a 10-year update and supplement to 1998, Rev. Mod. Phys. 70, 1265.

Search for short-lived axions

Abstract The original version of the axion was ruled out several years ago but a new variant required a second round of experimental searches. The newer, heavier, shorter-lived axion should have been detected following neutron capture on the protons in a recent ILL experiment. The null ILL result obtains strong limits within an important mass range. The experimental implication is that the axion is not the source of the puzzling narrow positron emission lines observed in heavy-ion collisions.

Decays of the lowestT=2state inTi44

The /sup 46/Ti(p,t)/sup 44/Ti reaction is used to populate the lowest T = 2 level and decay products from the level are detected in coincidence. The branching ratio for isospin forbidden ..cap alpha.. decay to /sup 40/Ca(g.s.) is GAMMA/sub b//GAMMA = (32 +- 5) %; the directly measured ..gamma..-decay branching ratio is GAMMA/sub ..gamma..//GAMMA = (54 +- 11) %. The proton decay branching ratio is found to be less than 4%.

Measurement of two‐body deuteron photodisintegration at high photon energies and θcm=90°

We report preliminary results from a measurement of the process 2H(γ,p)n at θCM=90° and for photon energies between 0.8 and 1.6 GeV. The results are compared to a conventional calculation based on meson‐exchange and to models based on sub‐nucleonic degrees of freedom. We find strong disagreement with the meson‐exchange calculation, and best agreement with simple constituent counting at the highest energies.

Decays of Lowest T=2 State in Ti-44

The /sup 46/Ti(p,t)/sup 44/Ti reaction is used to populate the lowest T = 2 level and decay products from the level are detected in coincidence. The branching ratio for isospin forbidden ..cap alpha.. decay to /sup 40/Ca(g.s.) is GAMMA/sub b//GAMMA = (32 +- 5) %; the directly measured ..gamma..-decay branching ratio is GAMMA/sub ..gamma..//GAMMA = (54 +- 11) %. The proton decay branching ratio is found to be less than 4%.

Decays of the lowest T = 2 state in /sup 44/Ti

The /sup 46/Ti(p,t)/sup 44/Ti reaction is used to populate the lowest T = 2 level and decay products from the level are detected in coincidence. The branching ratio for isospin forbidden ..cap alpha.. decay to /sup 40/Ca(g.s.) is GAMMA/sub b//GAMMA = (32 +- 5) %; the directly measured ..gamma..-decay branching ratio is GAMMA/sub ..gamma..//GAMMA = (54 +- 11) %. The proton decay branching ratio is found to be less than 4%.