Abstract
Various phenomenological studies indicate that the mixing angle
\$þeta\_K\_1\$ of \$K\_1A\$ and \$K\_1B\$, the strange partners of the
axial-vector mesons \$a\_1(1260)\$ and \$b\_1(1235)\$, respectively, lies in the
vicinity of \$35^\circ\$ or \$55^\circ\$, but whether this angle is larger or
smaller than \$45^\circ\$ still remains controversial. When the
\$f\_1(1285)\$-\$f\_1(1420)\$ mixing angle \$þeta\_^3P\_1\$ and the
\$h\_1(1170)\$-\$h\_1(1380)\$ mixing angle \$þeta\_^1P\_1\$ are determined from the
mass relations, they depend on the masses of \$K\_1A\$ and \$K\_1B\$, which in
turn depend on the mixing angle \$þeta\_K\_1\$. We show that the approximate
decoupling of the light \$qq\$ state from the heavier \$s s\$ state,
which is empirically valid for vector, tensor and \$3^--\$ mesons, when applied
to isoscalar axial-vector mesons, will enable us to discriminate different
solutions of \$þeta\_^3P\_1\$ and \$þeta\_^1P\_1\$ and pick up
\$þeta\_K\_135^\circ\$. Indeed, for \$þeta\_K\_155^\circ\$, the
predicted \$þeta\_^1P\_1\$ disagrees sharply with the recent lattice
calculation and the implied large \$ss\$ content of \$h\_1(1170)\$ and \$q\bar
q\$ component of \$h\_1(1380)\$ cannot explain the observation of their strong
decays. We conclude that \$þeta\_K\_1\$ is smaller than \$45^\circ\$.
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