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

Abstract

Parity nonconservation in pp scattering has been studied by measuring the helicity dependence of the cross section, Az^ia* -<j~)/(cr + + cr~), for longitudinally polarized incident protons of 45 MeV. We found A z -(-1.50±0.22)x 10~7 for the angular range 23° to 52° (laboratory frame). The uncertainty is the root square sum of the error of the measured asymmetry (±0.19xl0~7), the error of the applied corrections ( ± 0.05 x 10 ~7), and of various systematic errors ( ± 0.09 x 10 ~7). This is the most accurate result ever obtained on parity nonconservation in the nucleon-nucleon interaction.

Parity violation in proton-proton scattering at 221 MeV

“…In the context of the weak meson exchange model [2], the TRIUMF measurement of A z determines primarily the weak ρ-meson-nucleon coupling constant h , where the superscripts refer to isospin change [3]. Precision results already obtained by the SIN group at 45 MeV [4] and the Bonn group at 13.6 MeV [5] the results of other parity violation experiments. They are needed, for example, in calculations of the proton anapole moment [6], one of the radiative corrections to the electron-nucleon isovector axial form factor in experiments such as SAMPLE [7] and G 0 [8].…”

“…Until the TRIUMF experiment, the coupling constants were very poorly constrained by experiment. Figure 14 shows the limits on the weak meson-nucleon couplings h pp ρ and h pp ω now imposed by the low energy results [4,5] and the present TRIUMF result. The error bands are based on a calculation by Carlson et al [28] assuming the Argonne v 18 (AV-18) potential [37], the Bonn 2000 (CD-Bonn) [38] strong interaction coupling constants, and including all partial waves up to J=8.…”

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

“…It has been over half a century since Lee and Yang first suggested the possibility of parity non-conservation in the weak interaction [45], which was confirmed expermentially shortly thereafter by Wu et al [46][47][48][49][50]. Modern day experimental [51][52][53][54][55][56][57][58][59][60] and theoretical [61][62][63][64][65] studies have given attention to parity violating two-nucleon processes, where the strong interactions are most precisely understood. These include proton-neutron fusion, p + n → d + γ, and elastic proton scattering,…”

Energy dependence of the parity-violating asymmetry of circularly polarized photons indγ⃗→npin pionless effective field theory

“…A number of PV observables in two-nucleon systems can in principle be used to constrain the PV part of the nucleon-nucleon interaction. In addition to proton-proton scattering [6][7][8][9], a particularly prominent example is the photon angular asymmetry A γ in the capture of polarized neutrons on unpolarized protons, which in terms of the traditional meson exchange models provides information on the PV pion-nucleon coupling. The NPDGamma experiment at Oak Ridge National Laboratory's Spallation Neutron Source is currently determining this asymmetry with the aim of significantly improving on previous results [10].…”