A
bstract
We report a measurement of the electric dipole moment of the
τ
lepton (
dτ
) using an 833 fb
−
1
data sample collected near the Υ(4
S
) resonance, with the Belle detector at the KEKB ...asymmetric-energy
e
+
e
−
collider. Using an optimal observable method, we obtain the real and imaginary parts of
d
τ
as Re(
d
τ
) = (
−
0
.
62
±
0
.
63)
×
10
−
17
e
cm and Im(
d
τ
) = (
−
0
.
40
±
0
.
32)
×
10
−
17
e
cm, respectively. These results are consistent with null electric dipole moment at the present level of experimental sensitivity and improve the sensitivity by about a factor of three.
A
bstract
We report a search for the charged-lepton flavor violation in Υ(2
S
) →
ℓ
∓
τ
±
(
ℓ
=
e, μ
) decays using a 25 fb
−
1
Υ(2
S
) sample collected by the Belle detector at the KEKB
e
+
e
−
...asymmetric-energy collider. We find no evidence for a signal and set upper limits on the branching fractions (
B
) at 90% confidence level. We obtain the most stringent upper limits:
B
(Υ(2
S
)
→ μ
∓
τ
±
)
<
0
.
23
×
10
−
6
and
B
(Υ(2
S
)
→ e
∓
τ
±
)
<
1
.
12
×
10
−
6
.
A
bstract
Charged-lepton-flavor-violation is predicted in several new physics scenarios. We update the analysis of
τ
lepton decays into a light charged lepton (
ℓ
=
e
±
or
μ
±
) and a vector meson (
...V
0
=
ρ
0
,
ϕ
,
ω
,
K
*0
, or
K
¯
*0
) using 980 fb
−
1
of data collected with the Belle detector at the KEKB collider. No significant excess of such signal events is observed, and thus 90% credibility level upper limits are set on the
τ
→
ℓV
0
branching fractions in the range of (1.7–4
.
3) × 10
−
8
. These limits are improved by 30% on average from the previous results.
A
bstract
We measure the branching fractions and
CP
asymmetries for the singly Cabibbo-suppressed decays
D
0
→
π
+
π
−
η
,
D
0
→
K
+
K
−
η
, and
D
0
→
ϕη
, using 980 fb
−
1
of data from the Belle ...experiment at the KEKB
e
+
e
−
collider. We obtain
B
D
0
→
π
+
π
−
η
=
1.22
±
0.02
stat
±
0.02
syst
±
0.03
B
ref
×
10
−
3
,
B
D
0
→
K
+
K
−
η
=
1.80
−
0.06
+
0.07
stat
±
0.04
syst
±
0.05
B
ref
×
10
−
4
,
B
D
0
→
ϕη
=
1.84
±
0.09
stat
±
0.06
syst
±
0.05
B
ref
×
10
−
4
,
where the third uncertainty (
B
ref
) is from the uncertainty in the branching fraction of the reference mode
D
0
→
K
−
π
+
η
. The color-suppressed decay
D
0
→
ϕη
is observed for the first time, with very high significance. The results for the
CP
asymmetries are
A
CP
D
0
π
+
π
−
η
=
0.9
±
1.2
stat
±
0.5
syst
%
,
A
CP
D
0
→
K
+
K
−
η
=
−
1.4
±
3.3
stat
±
1.1
syst
%
,
ACP
D
0
→
ϕη
=
−
1.9
±
4.4
stat
±
0.6
syst
%
.
The results for
D
0
→
π
+
π
−
η
are a significant improvement over previous results. The branching fraction and
A
CP
results for
D
0
→
K
+
K
−
η
, and the
ACP
result for
D
0
→
ϕη
, are the first such measurements. No evidence for
CP
violation is found in any of these decays.
A
bstract
We report the first measurement of the inclusive
e
+
e
−
→
b
b
¯
→
D
s
±
X
and
e
+
e
−
→
b
b
¯
→ D
0
/
D
¯
0
X
cross sections in the energy range from 10
.
63 to 11
.
02 GeV. Based on these ...results, we determine
σ
(
e
+
e
−
→
B
s
0
B
¯
s
0
X
) and
σ
(
e
+
e
−
→
B
B
¯
X
) in the same energy range. We measure the fraction of
B
s
0
events at Υ(10860) to be
f
s
= (
22.0
−
2.1
+
2.0
)%. We determine also the ratio of the
B
s
0
inclusive branching fractions
B
(
B
s
0
→ D
0
/
D
¯
0
X
)
/
B
(
B
s
0
→
D
s
±
X
) = 0
.
416 ± 0
.
018 ± 0
.
092. The results are obtained using the data collected with the Belle detector at the KEKB asymmetric-energy
e
+
e
−
collider.
A
bstract
Using a data sample of 980 fb
−
1
collected with the Belle detector at the KEKB asymmetric-energy
e
+
e
−
collider, we study the processes of
Ξ
c
0
→
Λ
K
¯
∗
0
,
Ξ
c
0
→
Σ
0
K
¯
∗
0
, and
Ξ
...c
0
→
Σ
+
K
∗
−
for the first time. The relative branching ratios to the normalization mode of
Ξ
c
0
→
Ξ
−
π
+
are measured to be
B
Ξ
c
0
→
Λ
K
¯
∗
0
/
B
Ξ
c
0
→
Ξ
−
π
+
=
0.18
±
0.02
stat
.
±
0.01
syst
.
,
B
Ξ
c
0
→
Σ
0
K
¯
∗
0
/
B
Ξ
c
0
→
Ξ
−
π
+
=
0.69
±
0.03
stat
.
±
0.03
syst
.
,
B
Ξ
c
0
→
Σ
+
K
∗
−
/
B
Ξ
c
0
→
Ξ
−
π
+
=
0.34
±
0.06
stat
.
±
0.02
syst
.
,
where the uncertainties are statistical and systematic, respectively. We obtain
B
Ξ
c
0
→
Λ
K
¯
∗
0
=
3.3
±
0.3
stat
.
±
0.2
syst
.
±
1.0
ref
.
×
10
−
3
,
B
Ξ
c
0
→
Σ
0
K
¯
∗
0
=
12.4
±
0.5
stat
.
±
0.5
syst
.
±
3.6
ref
.
×
10
−
3
,
B
Ξ
c
0
→
Σ
+
K
∗
0
=
6.1
±
1.0
stat
.
±
0.4
syst
.
±
1.8
ref
.
×
10
−
3
,
where the uncertainties are statistical, systematic, and from
B
Ξ
c
0
→
Ξ
−
π
+
, respectively. The asymmetry parameters
α
Ξ
c
0
→
Λ
K
¯
∗
0
and
α
Ξ
c
0
→
Σ
+
K
∗
−
are 0
.
15 ± 0
.
22(stat
.
) ± 0
.
04(syst
.
) and
−
0
.
52 ± 0
.
30(stat
.
) ± 0
.
02(syst
.
), respectively, where the uncertainties are statistical followed by systematic.
A
bstract
We report the first measurement of the exclusive cross sections
e
+
e
−
→
B
B
¯
,
e
+
e
−
→
B
B
¯
∗
, and
e
+
e
−
→
B
∗
B
¯
∗
in the energy range from 10
.
63 GeV to 11
.
02 GeV. The
B
...mesons are fully reconstructed in a large number of hadronic final states and the three channels are identified using a beam-constrained-mass variable. The shapes of the exclusive cross sections show oscillatory behavior with several maxima and minima. The results are obtained using data collected by the Belle experiment at the KEKB asymmetric-energy
e
+
e
−
collider.
We present a measurement of R_{K^{*}}, the branching fraction ratio B(B→K^{*}μ^{+}μ^{-})/B(B→K^{*}e^{+}e^{-}), for both charged and neutral B mesons. The ratio for the charged case R_{K^{*+}} is the ...first measurement ever performed. In addition, we report absolute branching fractions for the individual modes in bins of the squared dilepton invariant mass q^{2}. The analysis is based on a data sample of 711 fb^{-1}, containing 772×10^{6} BBover ¯ events, recorded at the ϒ(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^{+}e^{-} collider. The obtained results are consistent with standard model expectations.
A
bstract
We present measurements of the branching fractions for the decays
B
→
Kμ
+
μ
−
and
B
→
Ke
+
e
−
, and their ratio (
R
K
), using a data sample of 711 fb
−
1
that contains 772 × 10
6
B
B
¯
...events. The data were collected at the ϒ(4
S
) resonance with the Belle detector at the KEKB asymmetric-energy
e
+
e
−
collider. The ratio
R
K
is measured in five bins of dilepton invariant-mass-squared (
q
2
):
q
2
∈ (0
.
1
,
4
.
0)
,
(4
.
00
,
8
.
12)
,
(1
.
0
,
6
.
0), (10
.
2
,
12
.
8) and (
>
14
.
18) GeV
2
/c
4
, along with the whole
q
2
region. The
R
K
value for
q
2
∈ (1
.
0
,
6
.
0) GeV
2
/c
4
is
1.03
−
0.24
+
0.28
± 0
.
01. The first and second uncertainties listed are statistical and systematic, respectively. All results for
R
K
are consistent with Standard Model predictions. We also measure
CP
-averaged isospin asymmetries in the same
q
2
bins. The results are consistent with a null asymmetry, with the largest difference of 2.6 standard deviations occurring for the
q
2
∈ (1
.
0
,
6
.
0) GeV
2
/c
4
bin in the mode with muon final states. The measured differential branching fractions,
d
ℬ
/dq
2
, are consistent with theoretical predictions for charged
B
decays, while the corresponding values are below the expectations for neutral
B
decays. We have also searched for lepton-flavor-violating
B
→
Kμ
±
e
∓
decays and set 90% confidence-level upper limits on the branching fraction in the range of 10
−
8
for
B
+
→
K
+
μ
±
e
∓
, and
B
0
→
K
0
μ
±
e
∓
modes.
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