Precise relative γ-ray intensities for calibration of Ge semiconductor detectors

Low-energy weak interactions of quarks

▪ Abstract Anapole moments are parity-odd, time-reversal-even moments of the E1 projection of the electromagnetic current. Although it was recognized, soon after the discovery of parity violation i...

Atomic Parity Nonconservation and Nuclear Anapole Moments

https://www.fisica.unam.mx/erler/pdfs/0404291.pdf

Low energy tests of the weak interaction

We derive formalism for determining 2 + J → 2 infinite-volume transition amplitudes from finite-volume matrix elements. Specifically, we present a relativistic, model-independent relation between finite-volume matrix elements of external currents and the physically observable infinite-volume matrix elements involving two-particle asymptotic states. The result presented holds for states composed of two scalar bosons. These can be identical or non-identical and, in the latter case, can be either degenerate or non-degenerate. We further accommodate any number of strongly-coupled two-scalar channels. This formalism will, for example, allow future lattice QCD calculations of the $$\rho$$-meson form factor, in which the unstable nature of the $$\rho$$ is rigorously accommodated. In conclusion, we also discuss how this work will impact future extractions of nuclear parity and hadronic long-range matrix elements from lattice QCD.

Relativistic, model-independent, multichannel 2→2 transition amplitudes in a finite volume

Parity nonconservation in $p\ensuremath{-}p$ scattering has been studied by comparing the cross sections ${\ensuremath{\sigma}}^{+}$, and ${\ensuremath{\sigma}}^{\ensuremath{-}}$ for longitudinally polarized 45-MeV protons of positive and negative helicity. The longitudinal analyzing power is found to be ${A}_{z}=\ensuremath{-}(3.2\ifmmode\pm\else\textpm\fi{}1.1)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$. The quoted uncertainty includes the statistical error, the uncertainties of corrections applied, and estimates of systematic effects.

Measurement of Parity Nonconservation in pp Scattering at 45 MeV

Parity nonconservation in the pp interaction was studied by elastic scattering of 44.8 MeV longitudinally polarized protons. The scattering chamber consisted of a 100 bar ${\mathrm{H}}_{2}$ gas target, surrounded by a cylindrical ionization chamber in an axially symmetric arrangement, and a Faraday cup. The relative cross sections, ${\ensuremath{\sigma}}^{+}$ and ${\ensuremath{\sigma}}^{\ensuremath{-}}$, for positive and negative helicity of the incident beam, were measured by integrating the current from the Faraday cup and from the ionization chamber during 20 ms intervals, and digitizing the charges. The parity nonconserving longitudinal analyzing power ${A}_{z}=\frac{({\ensuremath{\sigma}}^{+}\ensuremath{-}{\ensuremath{\sigma}}^{\ensuremath{-}})}{({\ensuremath{\sigma}}^{+}+{\ensuremath{\sigma}}^{\ensuremath{-}})}$ was deduced from 1.4 \ifmmode\times\else\texttimes\fi{} ${10}^{6}$ individual measurements of ${p}_{z}{A}_{z}$, where ${p}_{z}\ensuremath{\simeq}0.83$ is the beam polarization. The emphasis is on quantitative treatments of instrumental effects, the most important of which is caused by the nonuniform distribution of residual transverse polarization components in the beam. The final result for the helicity dependence of the total nuclear pp cross section at a laboratory energy of 44.8 MeV is ${A}_{z}^{\mathrm{tot}}=\ensuremath{-}(2.31\ifmmode\pm\else\textpm\fi{}0.89)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$. The uncertainty includes the statistical error as well as the systematic uncertainties from transverse polarization, modulation of intensity, position, emittance, and energy of the beam associated with helicity reversal, double scattering, asymmetry from $\ensuremath{\beta}$ decay, and electronic cross talk. The result is compared to theoretical predictions and to related experiments.

W. Reichart

Papers

Measurement of Parity Nonconservation in pp Scattering at 45 MeV

Parity violation in proton-proton scattering at 45 MeV

Improved energy resolution of Van de Graaff accelerators

A quantitative monitor for beam intensity and polarization profiles