The
decay
B
0
s
→
ψ(
2
S
)
K
+
π
−
is
observed
using
a
data
set
corresponding
to
an
integrated
luminosity
of
3
.
0fb
−
1
collected
by
the
LHCb
experiment
in
pp
collisions
at
centre-of-mass
energies
of
7
and
8
TeV.
The
branching
fraction
relative
to
the
B
0
→
ψ(
2
S
)
K
+
π
−
decay
mode
is
measured
to
be
B
(
B
0
s
→
ψ(
2
S
)
K
+
π
−
)
B
(
B
0
→
ψ(
2
S
)
K
+
π
−
)
=
5
.
38
±
0
.
36
(
stat
)
±
0
.
22
(
syst
)
±
0
.
31
(
f
s
/
f
d
)
%
,
where
f
s
/
f
d
indicates
the
uncertainty
due
to
the
ratio
of
probabilities
for
a
b
quark
to
hadronise
into
a
B
0
s
or
B
0
meson.
Using
an
amplitude
analysis,
the
fraction
of
decays
proceeding
via
an
intermediate
K
∗
(
892
)
0
meson
is
measured
to
be
0
.
645
±
0
.
049
(
stat
)
±
0
.
049
(
syst
)
and
its
longitudinal
polarisation
fraction
is
0
.
524
±
0
.
056
(
stat
)
±
0
.
029
(
syst
)
.
The
relative
branching
fraction
for
this
component
is
determined
to
be
B
(
B
0
s
→
ψ(
2
S
)
K
∗
(
892
)
0
)
B
(
B
0
→
ψ(
2
S
)
K
∗
(
892
)
0
)
=
5
.
58
±
0
.
57
(
stat
)
±
0
.
40
(
syst
)
±
0
.
32
(
f
s
/
f
d
)
%
.
In
addition,
the
mass
splitting
between
the
B
0
s
and
B
0
mesons
is
measured
as
M
(
B
0
s
)
−
M
(
B
0
)
=
87
.
45
±
0
.
44
(
stat
)
±
0
.
09
(
syst
)
MeV
/
c
2
.