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

• Received 30 December 1986

DOI:https://doi.org/10.1103/PhysRevLett.58.1616