[en] The parametric resonance enhancement of the phase of neutrons due to non-Newtonian anomalous gravitation is considered. The existence of such resonances is confirmed by numerical calculations. A possible experimental scheme for observing this effect is discussed based on an existing neutron interferometer design.

[en] The NPDGamma collaboration reports results from the first phase of a measurement of the parity violating up-down asymmetry A_γ with respect to the neutron spin direction of γ rays emitted in the reaction n + p → d + γ using the capture of polarized cold neutrons on the protons in a liquid parahydrogen target. One expects parity-odd effects in the hadronic weak interaction between nucleons to be induced by the weak interaction between quarks. A_γ in n + p → d + γ is dominated by a ΔI = 1, ³S_1-³P₁ parity-odd transition amplitude in the n-p system. The first phase of the measurement was completed at the Los Alamos Neutron Science Center spallation source (LANSCE), with the result A_γ = (-1.2 ± 2.1 (stat.) ± 0.2 (sys.)) x 10^-7. We also report the first measurement of an upper limit for the parity-allowed left-right asymmetry in this reaction, with the result A_γLR = (-1.8 ± 1.9 (stat.) ± 0.2 (sys.)) x 10^-7. In this paper we give a detailed report on the theoretical background, experimental setup, measurements, extraction of parity-odd and parity-allowed asymmetries, analysis of potential systematic effects, and LANSCE results. The asymmetry has an estimated size of 5 x 10^-8 and the aim of the NPDGamma collaboration is to measure it to 1 x 10^-8. The second phase of the measurement will be performed at the Spallation Neutron Source at Oak Ridge National Laboratory.

[en] The decay of the free neutron into a proton, electron, and antineutrino is the prototype semileptonic weak decay and is the simplest example of nuclear beta decay. It played a key role in the early Universe as it determined the ratio of neutrons to protons during the era of primordial light element nucleosynthesis. Neutron decay is physically related to important processes in solar physics and neutrino detection. The mean neutron lifetime has been the subject of more than 20 major experiments done, using a variety of methods, between 1950 and the present. The most precise recent measurements have stated accuracies approaching 0.1%, but are not in good agreement as they differ by as much as 5σ using quoted uncertainties. The history of neutron lifetime measurements is reviewed and the different methods used are described, giving important examples of each. The discrepancies and some systematic issues in the experiments that may be responsible are discussed, and it is shown by means of global averages that the neutron lifetime is likely to lie in the range of 880-884 s. Plans and prospects for future experiments are considered that will address these systematic issues and improve our knowledge of the neutron lifetime.

[en] We study the expected performance of the proposed fundamental neutron physics beamline at the upgraded High Flux Isotope Reactor at Oak Ridge National Laboratory. A curved neutron guide transmits the neutrons from the new cold source into a guide hall. A novel feature of the proposed guide is the use of vertical focusing to increase the flux for experiments that require relatively small cross-section beams. We use the simulation code IB to model straight, multi-channel curved, and tapered guides of various M. values. Guide performance for the current NPDGamma and proposed abBA experiments is evaluated

[en] In recent years, an energetic experimental program has set quite stringent limits on a possible ''non-1/r²'' dependence on gravity at short length scales. This effort has been largely driven by the predictions of theories based on compactification of extra spatial dimensions. It is characteristic of many such theories that the strength and length scales of such anomalous gravity are not clearly determined from first principles. As a result, it is productive to extend the current limits the range and strength of such hypothetical interactions. As a heavy, neutral, and (almost) stable particle, the neutron provides an ideal probe for the study of such hypothetical interactions at very short range. In this work, we describe methods based on neutron interferometry which have the capability to provide improved sensitivity non-Newtonian forces down to length scales at and below an nanometer

[en] The parametric resonance enhancement of the phase of neutrons due to non-Newtonian anomalous gravitation is considered. The existence of such resonances is confirmed by numerical calculations. A possible experimental scheme for observing this effect is discussed based on an existing neutron interferometer design.

[en] We discuss the coherent nature of neutron interactions and properties of low-energy neutrons with the view of the possibility to search for 'anomalous' forces with ranges from nuclear sizes up to the macroscopic scale.

[en] The optimization of the ballistic guide design for the SNS Fundamental Neutron Physics Beamline 8.9A line is described. With a careful tuning of the shape of the curve for the tapered section and the width of the straight section, this optimization resulted in more than a 75% increase in the neutron flux exiting the 33m long guide over a straight m=3.5 guide with the same length

[en] The Spallation Neutron Source (SNS), currently under construction at Oak Ridge National Laboratory with an anticipated start-up in early 2006, will provide the most intense pulsed beams of cold neutrons in the world. At a projected power of 1.4 MW, the time averaged fluxes and fluences of the SNS will approach those of high flux reactors. One of the flight paths on the cold, coupled moderator will be devoted to fundamental neutron physics. The fundamental neutron physics beamline is anticipated to include two beam-lines; a broad band cold beam, and a monochromatic beam of 0.89 nm neutrons for ultracold neutron (UCN) experiments. The fundamental neutron physics beamline will be operated as a user facility with experiment selection based on a peer reviewed proposal process. An initial program of five experiments in neutron decay, hadronic weak interaction and time reversal symmetry violation have been proposed

[en] Monte Carlo simulations are being performed to design and characterize the neutron optics components for the two fundamental neutron physics beamlines at the Spallation Neutron Source. Optimization of the cold beamline includes characterization of the guides and benders, the neutron transmission through the 0.89 nm monochromator, and the expected performance of the four time-of-flight choppers. The locations and opening angles of the choppers have been studied using a simple spreadsheet-based analysis that was developed for other SNS chopper instruments. The spreadsheet parameters are then optimized using Monte Carlo techniques to obtain the results presented in this paper. Optimization of the 0.89 nm beamline includes characterizing the double crystal monochromator and the downstream guides. The simulations continue to be refined as components are ordered and their exact size and performance specifications are determined