Abstract
Using a data sample of
s
=
13
TeV
proton-proton collisions collected by the CMS experiment at the LHC in 2017 and 2018 with an integrated luminosity of
103
fb
-
1
, the
B
s
0
→
ψ
(
2S
)
K
S
0
and
B
0
→
ψ
(
2S
)
K
S
0
π
+
π
-
decays are observed with significances exceeding 5 standard deviations. The resulting branching fraction ratios, measured for the first time, correspond to
B
(
B
s
0
→
ψ
(
2S
)
K
S
0
)
/
B
(
B
0
→
ψ
(
2S
)
K
S
0
)
=
(
3.33
±
0.69
(
stat
)
±
0.11
(
syst
)
±
0.34
(
f
s
/
f
d
)
)
×
10
-
2
and
B
(
B
0
→
ψ
(
2S
)
K
S
0
π
+
π
-
)
/
B
(
B
0
→
ψ
(
2S
)
K
S
0
)
=
0.480
±
0.013
(
stat
)
±
0.032
(
syst
)
, where the last uncertainty in the first ratio is related to the uncertainty in the ratio of production cross sections of
B
s
0
and
B
0
mesons,
f
s
/
f
d
.