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 H/sub 2/ gas target, surrounded by a cylindrical ionization chamber in an axially symmetric arrangement, and a Faraday cup. The relative cross sections, sigma/sup +/ and sigma/sup -/, 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/sub z/ = (sigma/sup +/-sigma/sup -/)/(sigma/sup +/+sigma /sup -/) was deduced from 1.4 x 10/sup 6/ individual measurements of p/sub z/A/sub z/, where p/sub z/approx. =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/sub z//sup tot/ = -(2.31 +- 0.89) x 10 /sup -7/. The uncertainty includes the statistical error as well as the systematic uncertainties from transverse polarization, modulation of intensity,more » position, emittance, and energy of the beam associated with helicity reversal, double scattering, asymmetry from ..beta.. decay, and electronic cross talk. The result is compared to theoretical predictions and to related experiments.« less

A new upper limit for the probability of spontaneous muonium to antimuonium conversion was established at P-M (M over bar) less than or equal to 8.3 x 10(-11) (90% C.L.) in 0.1 T magnetic field, which implies consequences for speculative extensions to the standard model. Coupling parameters in R-parity-violating supersymmetry and the mass of a flavor diagonal bileptonic gauge boson can be significantly restricted. A Z(8) model with radiative mass generation through heavy lepton seed and the minimal version of 331 models are disfavored. [S0031-9007(98)08068-5].

A new experiment has been set up at the Paul Scherrer Institut to search for muonium to antimuonium conversion. No event was found to fulfil the requested signature which consists of the coincident detection of both constituents of the antiatom in its decay. Assuming an effective (V - A) x (V - A) type interaction an improved upper limit is established for the conversion probability of P() less than or equal to 8 x 10(-9) (90% C.L.), which is almost 2 orders of magnitude lower compared to previous results and provides a sensitive test for theoretical extensions of the standard model.

In the standard model lepton number violating processes are forbidden, but are allowed in many extensions to it. Muonium to antimuonium conversion has been explicitly allowed in the framework of left‐right‐symmetric models or in supersymmetric models. A new experiment at PSI has demonstrated its ability to improve the sensitivity to such a rare process significantly.

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.

We have measured cross sections and analyzing powers in the continuum of the (p, αx) and (p, τx) reactions for 12C, 27Al, 58Ni, 90Zr and 209Bi target nuclei, using 72 MeV polarized protons. The systematics we have found in the behaviour of the differential cross section and of the analyzing power of the (p, αx) reaction is discussed and similarities in the shape of the 4He and 3He angular distributions are pointed out. For the 27Al(p, αx) and the 90Zr(p, αx) reactions as well as for the 58Ni(p, τx) reaction, a comparison with theoretical predictions of recently developed direct-reaction models is presented. It is shown that the MSDR model can describe successfully the cross section and the analyzing power of the (p, αx) reaction in the continuum. The influence of quasi-free processes in the (p, αx) reaction is demonstrated. We have found a surprisingly large analyzing power of the (p, αx) reaction at backward angles, especially for heavy nuclei, contrary to expectations from conventional preequilibrium models.

Carefully measured angular distributions in the 165Ho(α, 2n)167Tm reaction are reported. It is shown that the Gaussian substate population hypothesis is inadequate. An improved population model is proposed which takes into account the direct feeding through discrete γ-ray transitions in the yrast region. The experimental angular distribution coefficients can then be properly reproduced by the calculation. Unambiguous and nuclear model independent spin determinations are obtained.

Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Twitter Facebook Reddit LinkedIn Tools Icon Tools Reprints and Permissions Cite Icon Cite Search Site Citation R. Henneck, Ch. Jacquemart, J. Lang, M. Simonius, R. Balzer, W. Haeberli, S. Jaccard, W. Reichart, Ch. Weddigen; Parity violation in pp scattering at 45 MeV: Discussion of systematic error sources. AIP Conf. Proc. 1 March 1981; 69 (2): 1439–1441. https://doi.org/10.1063/1.32791 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentAIP Publishing PortfolioAIP Conference Proceedings Search Advanced Search |Citation Search