Nucleon matrix element of Weinberg's CP-odd gluon operator from the instanton vacuum

Nucleon Spin Structure from the Instanton Vacuum †

We discuss the evaluation of the nucleon isoscalar axial coupling, g (0) A , in the in-stanton vacuum, using the 1/N c expansion. This approach allows a fully consistent treatment of the U (1) A anomaly. We compute the nucleon matrix element of the topological charge density, N |F F |N , and show that it reduces to the matrix element of the divergence of the isoscalar axial quark current. Our a...

CP-odd nucleon potential.

Nucleon matrix elements of twist – 3 and 4 operators from the instanton vacuum †

The spin–dependent twist–3 and 4 nucleon matrix elements d (2) and f (2) describing power corrections to the Bjorken and Ellis–Jaffe sum rules are computed in the instanton vacuum. A systematic expansion in the small packing fraction of the instanton medium, ¯ ρ/ ¯ R ≪ 1, is performed. We find that the twist–3 matrix element d (2) is suppressed [of order (¯ ρ/ ¯ R) 4 ], while the twist–4 matrix...

Nucleon matrix elements of higher – twist operators from the instanton vacuum

We compute the nucleon matrix elements of QCD operators of twist 3 and 4 in the instanton vacuum. We consider the operators determining 1/Q 2 –power corrections to the Bjorken, Ellis–Jaffe and Gross–Llewellyn-Smith sum rules. The nucleon is described as a soliton of the effective chiral theory derived from instantons in the 1/N c –expansion. QCD operators involving the gluon field are systemati...

On the CP - odd Nucleon Potential

The CP-odd nucleon potential for different models of CP violation in the one meson exchange approximation is studied. It is shown that the main contribution is due to the π-meson exchange which leads to a simple one parameter CP-odd nucleon potential.