Subleading corrections to parity violating pion photoproduction
  We compute the photon asymmetry $B_\gamma$ for near threshold parity violating (PV) pion photoproduction through sub-leading order. We show that sub-leading contributions involve a new combination of PV couplings not included in previous analyses of hadronic PV. We argue that existing constraints on the leading order contribution to $B_\gamma$ -- obtained from the PV $\gamma$-decay of $^{18}$F -- suggest that the impact of the subleading contributions may be more significant than expected from naturalness argumen 
Shi-Lin Zhu, S. Puglia, B.R. Holstein, and M. J. Ramsey-Musolf