Determination of the η and η ′ Mixing Angle from the Pseudoscalar Transition Form Factors
Abstract
The possible range of
η−
η
′
mixing angle is determined from the transition form factors
F
ηγ
(
Q
2
)
and
F
η
′
γ
(
Q
2
)
with the help of the present experimental data. For such purpose, the quark-flavor mixing scheme is adopted and the pseudoscalar transition form factors are calculated under the light-cone pQCD framework, where the transverse momentum corrections and the contributions beyond the leading Fock state have been carefully taken into consideration. We construct a phenomenological expression to estimate the contributions to the form factors beyond the leading Fock state based on their asymptotic behavior at
Q
2
→0
and
Q
2
→∞
. By taking the quark-flavor mixing scheme, our results lead to
ϕ=
38.0
∘
±
1.0
∘
±
2.0
∘
, where the first error coming from experimental uncertainty and the second error coming from the uncertainties of the wavefunction parameters. The possible intrinsic charm component in
η
and
η
′
is discussed and our present analysis also disfavors a large portion of intrinsic charm component in
η
and
η
′
, e.g.
|
f
c
η
′
|≤50MeV
.