Measurement Of Parity Nonconservation Research Articles

Precision measurement of parity nonconservation in proton-proton scattering at 45 MeV.

Parity nonconservation in pp scattering has been studied by measuring the helicity dependence of the cross section, ${A}_{z}$=(${\ensuremath{\sigma}}^{+}$-${\ensuremath{\sigma}}^{\ensuremath{-}}$)/(${\ensuremath{\sigma}}^{+}$+${\ensuremath{\sigma}}^{\ensuremath{-}}$), for longitudinally polarized incident protons of 45 MeV. We found ${A}_{z}$=(-1.50\ifmmode\pm\else\textpm\fi{}0.22)\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}7}$ for the angular range 23\ifmmode^\circ\else\textdegree\fi{} to 52\ifmmode^\circ\else\textdegree\fi{} (laboratory). The uncertainty is the root square sum of the error of the measured asymmetry (\ifmmode\pm\else\textpm\fi{}0.19\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}7}$), the error of the applied corrections (\ifmmode\pm\else\textpm\fi{}0.05\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}7}$), and of various systematic errors (\ifmmode\pm\else\textpm\fi{}0.09\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}7}$). This is the most accurate result ever obtained on parity nonconservation in the nucleon-nucleon interaction.

Measurement of parity nonconservation in the proton-proton total cross section at 800 MeV.

We report a measurement of parity nonconservation in the transmission of 800-MeV longitudinally polarized protons through an unpolarized, 1-m liquid-hydrogen target. The dependence of transmission on beam properties was studied to measure and to correct for systematic errors. The measured longitudinal asymmetry in the total cross section is ${A}_{L}=[+2.4\ifmmode\pm\else\textpm\fi{}1.1(\mathrm{statistical})\ifmmode\pm\else\textpm\fi{}0.1(\mathrm{systematic})]\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$.

Atomic-beam measurement of parity nonconservation in cesium.

We present a new measurement of parity nonconservation in cesium. In this experiment, a laser excited the 6S\ensuremath{\rightarrow}7S transition in an atomic beam in a region of static electric and magnetic fields. The quantity measured was the component of the transition rate arising from the interference between the parity nonconserving amplitude, ${\mathrm{scrE}}_{\mathrm{PNC}}$, and the Stark amplitude, \ensuremath{\beta}E. Our results are Im${\mathrm{scrE}}_{\mathrm{PNC}/\mathrm{\ensuremath{\beta}}=\mathrm{\ensuremath{-}}1.65\ifmmode\pm\else\textpm\fi{}0.13}$ mV/cm and ${C}_{2p}$=-2\ifmmode\pm\else\textpm\fi{}2, where ${C}_{2p}$ is the proton-axial-vector--electron-vector neutral-current coupling constant. These results are in agreement with previous less precise measurements in cesium and with the predictions of the electroweak standard model. We give a detailed discussion of the experiment with particular emphasis on the treatment and elimination of systematic errors. This experimental technique will allow future measurements of significantly higher precision.

Measurement of parity nonconservation in atomic cesium.

Measurement of parity nonconservation in atomic cesium.

Measurement of Parity Nonconservation in Atomic Bismuth

Parity-nonconserving optical rotation has been observed and measured on the 8757-\AA{}A magnetic-dipole absorption line in atomic bismuth vapor. The result, $R\ensuremath{\equiv}\mathrm{Im}(\frac{{E}_{1}}{{M}_{1}})=(\ensuremath{-}10.4\ifmmode\pm\else\textpm\fi{}1.7)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$, is of the approximate size calculated with use of the Weinberg-Salam theory of the weak neutral-current interaction with ${{sin}^{2}\ensuremath{\theta}}_{\mathrm{W}}=0.23$.

Parity violating neutral current interactions and [formula omitted] transitions in hydrogenic ions

Measurement of parity nonconservation in magnetic dipole transitions between Zeeman split 2 S 1 2 states in hydrogenic ions is considered as a probe of the weak neutral current interaction between electrons and nucleons.

Measurement of Parity Nonconservation inppScattering at 45 MeV

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.

Sensitivity and the Role of Level Crossings in Measurements of Parity Nonconservation using Metastable Atoms

The author points out that experiments to measure parity nonconservation in metastable atoms, such as hydrogen in the 2S state, are not, in general, made more sensitive by operating near level crossings in a magnetic field. New possibilities related to this observation are mentioned.

Further measurements of parity non-conservation in inelastic electron scattering

We have extended our earlier measurements of parity violating asymmetries in the inelastic scattering of longitudinally polarized electrons from deuterium to cover the range 0.15≤ y≤0.36. The observed asymmetry shows only slight y dependence over this range. Our results are consistent with the expectations of the Weinberg-Salam model for a value of sin 2 θ w = 0.224±0.020.