Abstract
We study the processes
γ
γ
→
η
c
→
η
′
K
+
K
−
,
η
′
π
+
π
−
, and
η
π
+
π
−
using a data sample of
519
fb
−
1
recorded with the BABAR detector operating at the SLAC PEP-II asymmetric-energy
e
+
e
−
collider at center-of-mass energies at and near the
Υ
(
n
S
)
(
n
=
2
, 3, 4) resonances. This is the first observation of the decay
η
c
→
η
′
K
+
K
−
and we measure the branching fraction
Γ
(
η
c
→
η
′
K
+
K
−
)
/
(
Γ
(
η
c
→
η
′
π
+
π
−
)
=
0.644
±
0.03
9
stat
±
0.03
2
sys
. Significant interference is observed between
γ
γ
→
η
c
→
η
π
+
π
−
and the nonresonant two-photon process
γ
γ
→
η
π
+
π
−
. A Dalitz plot analysis is performed of
η
c
decays to
η
′
K
+
K
−
,
η
′
π
+
π
−
, and
η
π
+
π
−
. Combined with our previous analysis of
η
c
→
K
¯
K
π
, we measure the
K
∗
0
(
1430
)
parameters and the ratio between its
η
′
K
and
π
K
couplings. The decay
η
c
→
η
′
π
+
π
−
is dominated by the
f
0
(
2100
)
resonance, also observed in
J
/
ψ
radiative decays. A new
a
0
(
1700
)
→
η
π
resonance is observed in the
η
c
→
η
π
+
π
−
channel. We also compare
η
c
decays to
η
and
η
′
final states in association with scalar mesons as they relate to the identification of the scalar glueball.
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© 2021, The Author(s). Published by the American Physical Society