Determination of the Axial-Vector Weak Coupling Constant with Ultracold Neutrons

A precise measurement of the neutron decay $\beta$-asymmetry $A_0$ has been carried out using polarized ultracold neutrons (UCN) from the pulsed spallation UCN source at the Los Alamos Neutron Science Center (LANSCE). Combining data obtained in 2008 and 2009, we report $A_0 = -0.11966 \pm 0.00089_{-0.00140}^{+0.00123}$, from which we determine the ratio of the axial-vector to vector weak coupling of the nucleon $g_A/g_V = -1.27590_{-0.00445}^{+0.00409}$.Comment: 5 pages, 2 figure

New result for the neutron β\beta-asymmetry parameter A0A_0 from UCNA

The neutron $\beta$-decay asymmetry parameter $A_0$ defines the correlation between the spin of the neutron and the momentum of the emitted electron, which determines $\lambda=\frac{g_{A}}{g_{V}}$, the ratio of the axial-vector to vector weak coupling constants. The UCNA Experiment, located at the Ultracold Neutron facility at the Los Alamos Neutron Science Center, is the first to measure such a correlation coefficient using ultracold neutrons (UCN). Following improvements to the systematic uncertainties and increased statistics, we report the new result $A_0 = -0.12054(44)_{\mathrm{stat}}(68)_{\mathrm{syst}}$ which yields $\lambda\equiv \frac{g_{A}}{g_{V}}=-1.2783(22)$. Combination with the previous UCNA result and accounting for correlated systematic uncertainties produces $A_0=-0.12015(34)_{\mathrm{stat}}(63)_{\mathrm{syst}}$ and $\lambda\equiv \frac{g_{A}}{g_{V}}=-1.2772(20)$.Comment: 9 pages, 7 figures, updated to as-published versio

First direct constraints on Fierz interference in free neutron β\beta decay

Precision measurements of free neutron $\beta$-decay have been used to precisely constrain our understanding of the weak interaction. However the neutron Fierz interference term $b_n$, which is particularly sensitive to Beyond-Standard-Model tensor currents at the TeV scale, has thus far eluded measurement. Here we report the first direct constraints on this term, finding $b_n = 0.067 \pm 0.005_{\text{stat}} {}^{+0.090}_{- 0.061}{}_{\text{sys}}$, consistent with the Standard Model. The uncertainty is dominated by absolute energy reconstruction and the linearity of the beta spectrometer energy response

First Measurement of the Neutron β\beta-Asymmetry with Ultracold Neutrons

We report the first measurement of angular correlation parameters in neutron $\beta$-decay using polarized ultracold neutrons (UCN). We utilize UCN with energies below about 200 neV, which we guide and store for $\sim 30$ s in a Cu decay volume. The $\vec{\mu}_n \cdot \vec{B}$ potential of a static 7 T field external to the decay volume provides a 420 neV potential energy barrier to the spin state parallel to the field, polarizing the UCN before they pass through an adiabatic fast passage (AFP) spin-flipper and enter a decay volume, situated within a 1 T, $2 \times 2\pi$ superconducting solenoidal spectrometer. We determine a value for the $\beta$-asymmetry parameter $A_0$, proportional to the angular correlation between the neutron polarization and the electron momentum, of $A_0 = -0.1138 \pm 0.0051$.Comment: 4 pages, 2 figures, 1 table, submitted to Phys. Rev. Let

Student Satisfaction and Performance in an Online Teacher Certification Program

The article presents a study which demonstrates the effectiveness of an online post baccalaureate teacher certification program developed by a Wisconsin university. The case method approach employing multiple methods and multiple data sources were used to investigate the degree to which pre-service teachers were prepared to teach. It was concluded that the study supports online delivery as an effective means of teacher preparation, but it was limited in the number of students followed into their first year of teaching

Reconstructing the Inflaton Potential---in Principle and in Practice

Generalizing the original work by Hodges and Blumenthal, we outline a formalism which allows one, in principle, to reconstruct the potential of the inflaton field from knowledge of the tensor gravitational wave spectrum or the scalar density fluctuation spectrum, with special emphasis on the importance of the tensor spectrum. We provide some illustrative examples of such reconstruction. We then discuss in some detail the question of whether one can use real observations to carry out this procedure. We conclude that in practice, a full reconstruction of the functional form of the potential will not be possible within the foreseeable future. However, with a knowledge of the dark matter components, it should soon be possible to combine intermediate-scale data with measurements of large-scale cosmic microwave background anisotropies to yield useful information regarding the potential.Comment: 39 pages plus 2 figures (upon request:[email protected]), LaTeX, FNAL--PUB--93/029-A; SUSSEX-AST 93/3-

Search for neutron dark decay: n → χ + e⁺e⁻

In January, 2018, Fornal and Grinstein proposed that a previously unobserved neutron decay branch to a dark matter particle (χ) could account for the discrepancy in the neutron lifetime observed in two different types of experiments. One of the possible final states discussed includes a single χ along with an e⁺e⁻ pair. We use data from the UCNA (Ultracold Neutron Asymmetry) experiment to set limits on this decay channel. Coincident electron-like events are detected with ∼ 4π acceptance using a pair of detectors that observe a volume of stored Ultracold Neutrons (UCNs). We use the timing information of coincidence events to select candidate dark sector particle decays by applying a timing calibration and selecting events within a physically-forbidden timing region for conventional n → p + e⁻ + ν̅_e decays. The summed kinetic energy (E_(e⁺e⁻)) from such events is reconstructed and used to set limits, as a function of the χ mass, on the branching fraction for this decay channel

Clinical disorders affecting mesopic vision

Vision in the mesopic range is affected by a number of inherited and acquired clinical disorders. We review these conditions and summarize the historical background, describing the clinical characteristics alongside the genetic basis and molecular biological mechanisms giving rise to rod and cone dysfunction relevant to twilight vision. The current diagnostic gold standards for each disease are discussed and curative and symptomatic treatment strategies are summarized