8
3.45 3.5 3.55 3.6 3.65 3.7
M (GeV/c2)
K s0K±π±
)2c/VeG
200.0(
/
stnevE
104 Combined
γχ
γηc (J 2S)
c
KKπ
103 π0s KKπ
s
Other bkg
Continuum bkg
102
10
1
3.45 3.5 3.55 3.6 3.65 3.7
M
K+K π0
(GeV/c2)
)2c/VeG
200.0(
/
stnevE
104
Combined
γχ
γηc (J 2S)
c
103 KKπ0π0
KKπ0
Other bkg
Continuum bkg
102
10
1
3.58 3.6 3.62 3.64 3.66 3.68 3.7
M (GeV/c2)
K s0K±π±
)2c/VeG
200.0(
/
stnevE
140
Combined γχ
120 γηc (J 2S)
c
KKπ
s
100 π0KKπ
s
Other bkg
80 Continuum bkg
60
40
20
0
3.58 3.6 3.62 3.64 3.66 3.68 3.7
M
K+K π0
(GeV/c2)
)2c/VeG
200.0(
/
stnevE
(a) (b)
140
(c) (d) C γχombined
120 γηc (J 2S)
c
KKπ0π0
100 KKπ0
Other bkg
80 Continuum bkg
60
40
20
0
FIG. 2. The distributions of the invariant mass spectra of KK¯π. The fit results in the whole fit range (a,b) and in the
range only containing ηc(2S) signal (c,d). (a) and (c) are for the K S0K±π∓ mode, (b) and (d) are for the K+K−π0 mode.
Dots with error bars are data, blue solid curves are the best results from the simultaneous fits. The blue dashed lines are the
ηc(2S)signals,andtheotherdashedlinesarebackgrounds,amongwhichthepink,red,black,greenandcyanonesarefromthe
ψ(3686) π0+KK¯π events, the ψ(3686) KK¯π events, the ψ(3686) γχc1,2 events, other contributions, and continuum
→ → →
contribution, respectively. For plots (a) and (c), thedata statistics is summed overthe two charge conjugated modes.
The line-shapes of the χ are described with the fromMCsimulation,withtheFSRandnon-FSRcompo-
c1,2
simulated MC shapes convoluted with a single Gaussian nentsreweightedbycorrectedf . Weaddthecontinu-
FSR
functionforthedifferenceinresolutionofM KK¯π between umbackgroundscontributionwithshiftedmassspectrum
data andMC simulation,and their parametersarefloat- shape, and the numbers of continuum backgrounds are
ed in the fit. fixed. We describe all other smooth backgrounds with
the shape fixed to that from the inclusive MC sample
WeuseaNovosibirskfunction[27]toparameterizethe
while the number of events are floated.
backgrounds of ψ(3686) π0KK¯π events from data,
→
with the shape of the function and the number of back- The yields of the η (2S) signal are 692 42 in the
c
ground events fixed. For the background of ψ(3686) K+K−π0 mode and 963 58 in the K0K±±π∓ mode.
KK¯π with and without γ , the shape is extract→ ed From the signal MC sim± ulations, we oS btain the effi-
FSR