Operator product expansions are applied to dilaton-axion four-point
functions. In the expansions of the bilocal fields Φ~Φ~,
C~C~ and Φ~C~, the conformal fields which
are symmetric traceless tensors of rank l and have dimensions δ=2+l or
8+l+η(l) and η(l)=O(N−2) are identified. The
unidentified fields have dimension δ=λ+l+η(l) with λ≥10. The anomalous dimensions η(l) are calculated at order
O(N−2) for both 2−1/2(−Φ~Φ~+C~C~) and 2−1/2(Φ~C~+C~Φ~) and are found to be the same, proving U(1)Y
symmetry. The relevant coupling constants are given at order O(1).Comment: 27 pages, 1 graph, 12 figures, Corrections in eqns. (1.10), (1.11