Parity violation in proton-proton scattering from chiral effective field theory

We present a calculation of the parity-violating longitudinal asymmetry in proton-proton scattering. The calculation is performed in the framework of chiral effective field theory which is applied systematically to both the parity-conserving and parity-violating interactions. The asymmetry is calculated up to next-to-leading order in the parity-odd nucleon-nucleon potential. At this order the asymmetry depends on two parity-violating low-energy constants: the weak pion-nucleon coupling constant $h_\pi$ and one four-nucleon contact coupling. By comparison with the existing data, we obtain a rather large range for $h_\pi= (1.1\pm 2)\cdot 10^{-6}$. This range is consistent with theoretical estimations and experimental limits, but more data are needed to pin down a better constrained value. We conclude that an additional measurement of the asymmetry around 125 MeV lab energy would be beneficial to achieve this goal.