T. Maurer, T. Burch, L. Ya. Glozman, C. B. Lang, D. Mohler, A. Schäfer
We report lattice QCD results on the axial charges of ground and excited
nucleon states of both parities. This is the first study of these quantities
with approximately chiral (CI) fermions. Two energy levels in the range of the
negative parity resonances N*(1535) and N*(1650) are observed and we determine
the axial charge for both. We obtain a small axial charge for one of them,
which is consistent with the chiral symmetry restoration in this state as well
as with the small axial charge of the N*(1535) predicted within the quark
model. This result agrees with the findings of Takahashi et al. obtained with
Wilson quarks which violate chiral symmetry for finite lattice spacing. At the
same time for the other observed negative parity state we obtain a large axial
charge, that is close to the axial charge of the nucleon. This is in
disagreement both with the quark model prediction as well as with the chiral
restoration but allows for an interpretation as an s-wave {\pi} N state.
View original:
http://arxiv.org/abs/1202.2834
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