Journal of Research of the National Institute of Standards and Technology articles from July 2005

Journal of Research of the National Institute of Standards and Technology archives from July 2005

Papers and posters presented at the April 2004 International Conference on Precision Measurements with Slow Neutrons at the National Institute of Standards and Technology.
July 1, 2005... Preface This Special Issue of the Journal of Research of the National Institute of Standards and Technology (Parts 1 and 2) contains papers from the International Conference on Precision Measurements with Slow Neutrons held at the National...

Precision measurements with slow neutrons: April 5-7, 2004.(Calendar)
July 1, 2005... Program Sunday, April 4, 2004 -- Washingtonian Hotel 7:00 pm Reception Monday, April 5, 2004 -- NIST, Green Auditorium 9:00 am Opening Remarks -- Dr. Lisa Karam, Acting Chief, Ionizing Radiation...

Radiative corrections for neutron decay and search for new physics.
July 1, 2005... The expected increased accuracy of neutron [beta]-decay experiments at the new Spallation Neutron Source could result in more stringent tests of the Standard Model. For an unambiguous search for new physics in neutron decay experiments and for...

Standard model treatment of the radiative corrections to neutron [beta]-decay.
July 1, 2005... Starting with the Standard Model electroweak Lagrangian, the radiative corrections to neutron [beta]-decay are obtained. Nucleon compositeness is considered by appropriate parameterization of the nucleon weak transition current and...

Measurement of the neutron lifetime by counting trapped protons.
July 1, 2005... We measured the neutron decay lifetime by counting in-beam neutron decay recoil protons trapped in a quasi-Penning trap. The absolute neutron beam fluence was measured by capture in a thin [.sup.6]LiF foil detector with known efficiency. The...

Measurement of the neutron lifetime using a gravitational trap and a low-temperature Fomblin coating.
July 1, 2005... We present a new value for the neutron lifetime of 878.5 = [0.7.sub.stat.] [+ or -] [0.3.sub.syst]. This result differs from the world average value by 6.5 standard deviations and by 5.6 standard deviations from the previous most precise...

Determination of the neutron lifetime using magnetically trapped neutrons.
July 1, 2005... We report progress on an experiment to measure the neutron lifetime using magnetically trapped neutrons. Neutrons are loaded into a 1.1 T deep superconducting Ioffe-type trap by scattering 0.89 nm neutrons in isotopically pure superfluid...

First ever storage of ultracold neutrons in a magnetic trap made of permanent magnets.
July 1, 2005... Further improvement in the accuracy of any neutron lifetime experiment by means of ultracold neutrons (UCN) in material bottles is limited due to unavoidable systematic effects when the UCN are reflected from the walls. However, such effects...

Neutron lifetime experiment based on an accordion-like UCN storage volume coated with "low temperature Fomblin".
July 1, 2005... A new type of per-fluorinated polymer, "Low Temperature Fomblin," has been tested as a wall coating in an ultracold neutron (UCN) storage experiment using a gravitational storage system. The data show a UCN reflection loss coefficient [eta] as...

A superconducting magnet UCN trap for precise neutron lifetime measurements.
July 1, 2005... Finite-element methods along with Monte Carlo simulations were used to design a magnetic storage device for ultracold neutrons (UCN) to measure their lifetime. A setup was determined which should make it possible to confine UCN with negligible...

On the measurement of the neutron lifetime using ultracold neutrons in a vacuum quadrupole trap.
July 1, 2005... We present a conceptual design for an experiment to measure the neutron lifetime (~886 s) with an accuracy of [10.sup.-4]. The lifetime will be measured by observing the decay rate of a sample of ultracold neutrons (UCN) confined in vacuum in a...

Chaotic scattering and escape times of marginally trapped ultracold neutrons.
July 1, 2005... We compute classical trajectories of Ultracold neutrons (UCNs) in a supercon-ducting Ioffe-type magnetic trap using a symplectic integration method. We find that the computed escape time for a particular set of initial conditions (momentum and...

The beta-, neutrino- and proton-asymmetry in neutron [beta]-decay.
July 1, 2005... This article describes measurements of angular-correlation coefficients in the decay of free neutrons with the superconducting spectrometer PERKEO II. A method for measuring the [beta]-asymmetry coefficient A is presented, as well as a new...

Project of neutron beta-decay A-asymmetry measurement with relative accuracy of (1-2) X [10.sup.-3].
July 1, 2005... We are going to use a polarized cold neutron beam and an axial magnetic field in the shape of a bottle formed by a superconducting magnetic system. Such a configuration of magnetic fields allows us to extract the decay electrons inside a...

Measurement of neutron decay parameters--the abBA experiment.
July 1, 2005... We are developing an experiment to measure the correlations a, A, and B, and the Fierz interference term b in neutron decay, with a precision of approximately [10.sup.-4]. The experiment uses an electromagnetic spectrometer in combination with...

Determination of the electron-antineutrino angular correlation coefficient [a.sub.0] in unpolarized neutron [beta]-decay.
July 1, 2005... The coefficient [a.sub.0] has been derived from a measurement of the integral spectrum of recoil protons stored in a quasi-Penning trap with inhomogeneous magnetic field and adiabatic focusing onto an electro-static mirror of potential variable...

Proposed measurement of the beta-neutrino correlation in neutron decay.
July 1, 2005... Currently, the beta-neutrino asymmetry has the largest uncertainty (4%) of the neutron decay angular correlations. Without requiring polarimetry, this decay parameter can be used to measure [lambda]([g.sub.a]/[g.sub.v]), test...

On the measurement of the electron-neutrino correlation in neutron beta decay.
July 1, 2005... I present a new approach to the measurement of a, the electron-neutrino correlation, in neutron beta decay. A precise measurement of a can lead to a precise determination of ratio of the axial vector and vector coupling constants,...

Radiative neutron [beta]-decay in effective field theory.
July 1, 2005... We consider radiative [beta]-decay of the neutron in heavy baryon chiral perturbation theory. Nucleon-structure effects not encoded in the weak coupling constants [g.sub.A] and [g.sub.V] are determined at next-to-leading order in the chiral...

Search for radiative [beta]-decay of the free neutron.
July 1, 2005... Results of the first experiment to search for the radiative decay mode of the free neutron are reported. The [gamma]-spectrum was studied in the energy region from 35 keV to 100 keV in six Cs(Tl) scintillators, each set at an angle of...

Detecting the radiative decay mode of the neutron.
July 1, 2005... Beta decay of the neutron into a proton, electron, and electron antineutrino is occasionally accompanied by the emission of a photon. Despite decades of detailed experimental studies of neutron beta-decay, this rare branch of a fundamental weak...

Detector development for the abBA experiment.
July 1, 2005... We have developed a new type of field-expansion spectrometer to measure the neutron beta decay correlations (a, b, B, and A). A precision measurement of these correlations places stringent requirements on charged particle detectors. The design...

A backscatter suppressed electron detector for the measurement of "a".
July 1, 2005... A new method of measuring the electron-antineutrino angular correlation coefficient, little "a", from neutron decay--to be performed at the National Institute of Standards and Technology--will require an electron spectrometer that strongly...

Monte Carlo study of the abBA experiment: detector response and physics analysis.
July 1, 2005... The abBA collaboration proposes to conduct a comprehensive program of precise measurements of neutron [beta]-decay coefficients a (the correlation between the neutron momentum and the decay electron momentum), b (the electron energy spectral...

Simulation of charged particle trajectories in the neutron decay correlation experiment abBA.
July 1, 2005... The proposed neutron decay correlation experiment, abBA, will directly detect the direction of emission of decay protons and electrons as well as providing spectroscopic information for both particles. In order to provide this information, the...

Development of a position sensitive neutron detector with high efficiency and energy resolution for use at high-flux beam sources.
July 1, 2005... We are developing a high-efficiency neutron detector with 1 cm position resolution and coarse energy resolution for use at high-flux neutron source facilities currently proposed or under construction. The detector concept integrates a segmented...

The T-odd R and D correlations in beta decay.
July 1, 2005... We review and discuss the time-reversal-odd R and D correlations in neutron and nuclear beta decay. Key words: beta decay; CP-violation; physics beyond the Standard Model; time-reversal violation. 1. Introduction CP-violation...

Search for time reversal violating effects: R-correlation measurement in neutron decay.
July 1, 2005... An experiment aiming at the simultaneous determination of both transversal polarization components of electrons emitted in the decay of free neutrons begins data taking using the polarized cold neutron beam (FUNSPIN) from the Swiss Neutron...

Two coils resonant Ramsey's method for the measurement of time reversal invariance violation in neutron transmission.
July 1, 2005... It is proposed within the framework of Ramsey's method to register two-dimensional spectra, depending on the neutron phase and neutron energy, for measuring parity (P) and time (T) violating amplitudes of the interaction of polarized neutrons...

On the way to experimental test of the time reversal invariance in the nuclear reactions.
July 1, 2005... Time (T) violation can be related with charge-parity (CP) violation through the CPT theorem. The CP violation was discovered experimentally in the [K.sub.0]-meson decays about 35 years ago. The T violating interaction related with the CP...

A Ramsey's method with pulsed neutrons for a T-violation experiment.
July 1, 2005... A Ramsey's method with pulsed neutrons is discussed for neutron spin manipulation in a time reversal (T) symmetry violation experiment. The neutron spin ([s.sub.n]) is aligned to the direction of a vector product of the nuclear spin (I) and the...

Bounds on time reversal violation from polarized neutron capture with unpolarized targets.
July 1, 2005... We have analyzed constraints on parity-odd time-reversal noninvariant interactions derived from measurements of the energy dependence of parity-violating polarized neutron capture on unpolarized targets. As previous authors found, a...

Investigation of solid [D.sub.2] for UCN sources.(ultra-cold neutrons)
July 1, 2005... Solid deuterium (s[D.sub.2]) will be used for the production of ultra-cold neutrons (UCN) in a new generation of UCN sources. Scattering cross sections of UCN in s[D.sub.2] determine the source yield but until now have not been investigated. We...

Conference summary.(at University of Heidelberg about neutron-particle physics experiments )
July 1, 2005... The study of particle physics with low energy neutrons has a long history starting in the middle of the past century. During most of the time only a rather small number of researchers worked in this field, at least as compared to any of the...