Measurements of CP Violation in B 0 → D ∗− π + and B 0 → D − π + Decays
Abstract
We report measurements of time dependent decay rates for
B
0
→
D
(∗)−
π
+
decays and extraction of CP violation parameters that depend on
ϕ
3
. Using fully reconstructed
D
(∗)
π
events and partially reconstructed
D
∗
π
events from a data sample that contains 386 million
B
B
¯
pairs that was collected near the
Υ(4S)
resonance, with the Belle detector at the KEKB asymmetric energy
e
+
e
−
collider, we obtain the CP violation parameters
S
+
(
D
(∗)
π)
and
S
−
(
D
(∗)
π)
. We obtain
S
+
(
D
∗
π)=0.049±0.020(stat)±0.011(sys)
,
S
−
(
D
∗
π)=0.031±0.019(stat)±0.011(sys)
, and
S
+
(Dπ)=0.031±0.030(stat)±0.012(sys)
,
S
−
(Dπ)=0.068±0.029(stat)±0.012(sys)
.
These results are an indication of CP violation in
B
0
→
D
∗−
π
+
and
B
0
→
D
−
π
+
decays at the
2.5σ
and
2.2σ
levels, respectively. If we use the values of
R
D
(∗)
π
that are derived using assumptions of factorization and SU(3) symmetry, the branching fraction measurements for the
D
(∗)
s
π
modes, and lattice QCD calculations, we can restrict the allowed region of
|sin(2
ϕ
1
+
ϕ
3
)|
to be above 0.44 and 0.52 at 68% confidence level from the
D
∗
π
and
Dπ
modes, respectively.