Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Axial and pseudoscalar current correlators and their couplings to eta
  and etaprime mesons   Correlators of singlet and octet axial currents, as well as anomaly and
pseudoscalar densities have been studied using QCD sum rules. Several of these
sum rules are used to determine the couplings f^8_eta, f^0_eta, f^8_etaprime
and f^0_etaprime. We find mutually consistent values which are also in
agreement with phenomenological values obtained from data on various decay and
production rates. While most of the sum rules studied by us are independent of
the contributions of direct instantons and screening correction, the
singlet-singlet current correlator and the anomaly-anomaly correlator improve
by their inclusion.

31
The categories of this paper are: ao-sci
15
The categories of this paper are: nucl-ex
13
The categories of this paper are: quant-ph
35
The categories of this paper are: mtrl-th
33
The categories of this paper are: plasm-ph
2
The categories of this paper are: math
25
The categories of this paper are: patt-sol
6
The categories of this paper are: astro-ph
28
The categories of this paper are: alg-geom
37
The categories of this paper are: supr-con
29
The categories of this paper are: funct-an
4
The categories of this paper are: cond-mat
10
The categories of this paper are: q-bio
7
The categories of this paper are: hep-th
18
The categories of this paper are: econ
17
The categories of this paper are: q-fin