Measurement of the Generalized Forward Spin Polarizabilities of the Neutron

Abstract

The generalized forward spin polarizabilities ${\gamma }_0$ and ${\delta }_{LT}$ of the neutron have been extracted for the first time in a $Q^2$ range from 0.1 to 0.9 GeV${}^2$. Since ${\gamma }_0$ is sensitive to nucleon resonances and ${\delta }_{LT}$ is insensitive to the $\Delta$ resonance, it is expected that the pair of forward spin polarizabilities should provide benchmark tests of the current understanding of the chiral dynamics of QCD. The new results on ${\delta }_{LT}$ show significant disagreement with Chiral Perturbation Theory calculations, while the data for ${\gamma }_0$ at low $Q^2$ are in good agreement with a next-to-lead order Relativistic Baryon Chiral Perturbation theory calculation. The data show good agreement with the phenomenological MAID model.

5 pages, 2 figures, corrected typo in author name, published in PRL