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Measuring the P-odd Pion-Nucleon Coupling hπNN(1) in π+ Photoproton Production Near the Threshold

Jiunn-Wei Chen, Xiangdong Ji

hep-pharXiv:hep-ph/0011230

Abstract

We show that polarized gamma p -> π+ n in the threshold region is an excellent candidate for measuring the leading parity-violating pion-nucleon coupling hπNN(1) to an uncertainty of 20% if it has a natural size from dimensional analysis. The conclusion is based on a large unpolarized cross section, a new low-energy theorem for the photon polarization asymmetry at the threshold Aγ|th = 2 fπ(μp-μn) hπNN(1)/gA mN hπNN(1)/2, and its strong dominance at forward and backward angles in the threshold region.

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