Search arXiv⌕ Search

arXiv · 0704.2365

Neutron Beta Decay: Status and Future of the Asymmetry Measurement

Abstract

With more intense sources of cold and ultracold neutrons becoming available and with improved experimental techniques being developed, determination of |Vud| from neutron beta decay with a similar precision to that from from superallowed beta decays is within reach. Determination of |Vud| from neutron beta decay, free from nuclear corrections, hold the most promise for a further improvement of the determination of |Vud|. The current and future neutron beta decay correlation experiments including the UCNA experiment at Los Alamos National Laboratory are reviewed

Explore related subjects

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Takeyasu M. Ito. 2007-04-18. Neutron Beta Decay: Status and Future of the Asymmetry Measurement. https://arxiv.org/abs/0704.2365

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

Laser Spectroscopy of Thulium Isotopes Near the (N=82) Shell Closure: Nuclear Moment and Charge Radius of ${}^{152\mathrm{m}}\mathrm{Tm}$

We report on resonance ionization laser spectroscopy measurements performed on both neutron-deficient and neutron-rich thulium ($\mathrm{Tm}, Z=69$) isotopes. Isotope shifts were determined for three atomic ground-state transitions at wavelengths of $389.8\,\mathrm{nm}$, $388.4\,\mathrm{nm}$, and $388.8\,\mathrm{nm}$ in the isotopes ${}^{152\mathrm{m}}\mathrm{Tm}$, ${}^{153}\mathrm{Tm}$, ${}^{154\mathrm{m}}\mathrm{Tm}$, and ${}^{169}\mathrm{Tm}$. In addition, for the $389.8\,\mathrm{nm}$ transition, measurements were extended to the isotope ${}^{170}\mathrm{Tm}$, and the hyperfine structure was partially resolved for all five isotopes. For this transition, the isotope shift could be determined for one more isotope, ${}^{154\mathrm{m}}\mathrm{Tm}$. From the extracted hyperfine coupling constants, the nuclear magnetic dipole moment for ${}^{152\mathrm{m}}\mathrm{Tm}$ was determined for the first time, resulting in $μ\left({}^{152\mathrm{m}}\mathrm{Tm}\right) = 5.8(3) μ_\mathrm{N}$. Furthermore, the mean-square nuclear charge radius $δ\langle r^2\rangle^{152\mathrm{m},169} = -1.86(25)\,\mathrm{fm}^2$ for ${}^{152\mathrm{m}}\mathrm{Tm}$ was extracted from the measured isotope shifts.

nucl-ex↗

Measurement of the $^3$He Spin Structure Functions and Their Moments at Low Q$^2$

We report measurements of spin-dependent electron scattering from a polarized $^3$He target, $\vec{^3\textrm{He}}(\vec{e},e')X$, performed at the Thomas Jefferson National Accelerator Facility (Jefferson Lab). The $^3$He spin-dependent virtual-photoabsorption cross sections $σ_{TT}$ and $σ_{LT}$, or equivalently the spin structure functions $g_1$ and $g_2$, and their moments were extracted for $0.032 \leq Q^2 \leq 0.23$~GeV$^2$, with coverage from the two-body breakup threshold through the nucleon-resonance region. The moment $I_1(Q^2)$ reaches a plateau below $Q^2 \simeq 0.1$~GeV$^2$, consistent with the Gerasimov--Drell--Hearn (GDH) expectation, while the moment $I_{TT}(Q^2)$, still dominated by the finite-virtuality breakup response, peaks at $Q^2 \simeq 0.1$~GeV$^2$ and turns toward the expected GDH value. Together, the two moments constitute the first observation of a nucleus approaching its GDH sum-rule value at the real-photon point. The moments $I_2(Q^2)$ and $I_{LT}(Q^2)$ yield, respectively, the lowest-$Q^2$ nuclear test of the Burkhardt--Cottingham sum rule and the first nuclear test of the Schwinger sum rule. Besides testing fundamental sum rules, these data provide stringent benchmarks for ab initio calculations of the spin structure of light nuclei.

nucl-ex↗

Spin-Density Matrix Elements in the Reaction $γp \to ρ^-Δ^{++}$ at GlueX

The GlueX experiment, located in Hall D at Jefferson Lab, aims to map the full spectrum of light-quark mesons with an emphasis on hybrid mesons, states in which the gluonic field is excited and contributes to the quantum numbers of the meson. The search for exotic hybrid mesons requires a detailed understanding of the underlying production mechanisms. Polarization observables, such as the spin-density matrix elements (SDMEs), are an important experimental tool to investigate these mechanisms. The measurement of the unpolarized and polarized SDMEs in the photoproduction of $ρ^-Δ^{++}$ using GlueX data is reported. In this analysis, for the first time, the correct full formalism is applied in which the upper mesonic and lower baryonic systems are described by a joint spin-density matrix. A factorized model yields results consistent with those of the full model, suggesting that this simplified description may also be suitable for other reactions involving meson-baryon final states.

nucl-ex↗