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 for the first time the singly Cabibbo-suppressed decays
$$ ...{\Omega}_c^0\to {\Xi}^{-}{\pi}^{+} $$
Ω
c
0
→
Ξ
−
π
+
and Ω
−
K
+
and the doubly Cabibbo-suppressed decay
$$ {\Omega}_c^0\to {\Xi}^{-}{K}^{+} $$
Ω
c
0
→
Ξ
−
K
+
. Evidence for an
$$ {\Omega}_c^0 $$
Ω
c
0
signal in the
$$ {\Omega}_c^0 $$
Ω
c
0
→
Ξ
−
π
+
mode is reported with a significance of 4
.
5
σ
including systematic uncertainties. The ratio of branching fractions to the normalization mode
$$ {\Omega}_c^0 $$
Ω
c
0
→
Ω
−
π
+
is measured to be
$$ \mathcal{B}\left({\Omega}_c^0\to {\Xi}^{-}{\pi}^{+}\right)/\mathcal{B}\left({\Omega}_c^0\to {\Omega}^{-}{\pi}^{+}\right)=0.253\pm 0.052\left(\textrm{stat}.\right)\pm 0.030\left(\textrm{syst}.\right). $$
B
Ω
c
0
→
Ξ
−
π
+
/
B
Ω
c
0
→
Ω
−
π
+
=
0.253
±
0.052
stat
.
±
0.030
syst
.
.
No significant signals of
$$ {\Omega}_c^0\to {\Xi}^{-}{K}^{+} $$
Ω
c
0
→
Ξ
−
K
+
and Ω
−
K
+
modes are found. The upper limits at 90% confidence level on ratios of branching fractions are determined to be
$$ \mathcal{B}\left({\Omega}_c^0\to {\Xi}^{-}{K}^{+}\right)/\mathcal{B}\left({\Omega}_c^0\to {\Omega}^{-}{\pi}^{+}\right)<0.070 $$
B
Ω
c
0
→
Ξ
−
K
+
/
B
Ω
c
0
→
Ω
−
π
+
<
0.070
and
$$ \mathcal{B}\left({\Omega}_c^0\to {\Omega}^{-}{K}^{+}\right)/\mathcal{B}\left({\Omega}_c^0\to {\Omega}^{-}{\pi}^{+}\right)<0.29. $$
B
Ω
c
0
→
Ω
−
K
+
/
B
Ω
c
0
→
Ω
−
π
+
<
0.29
.
We search for lepton-flavor and lepton-number-violating τ decays into a lepton (ℓ= electron or muon) and two charged mesons (h,h′=π± or K±) using 854 fb−1 of data collected with the Belle detector at ...the KEKB asymmetric-energy e+e− collider. We obtain 90% confidence level upper limits on the τ→ℓhh′ branching fractions in the range (2.0–8.4)×10−8. These results improve upon our previously published upper limits by factors of about 1.8 on average.
Abstract
Results of a study of the
$$K^+ \rightarrow \pi ^{0} e^{+} \nu \gamma $$
K
+
→
π
0
e
+
ν
γ
decay at OKA setup are presented. More than 32,000 events of this decay are observed. The ...differential spectra over the photon energy and the photon–electron opening angle in kaon rest frame are presented. The branching ratios, normalized to that of
$$K_{e3}$$
K
e
3
decay are calculated for different cuts on
$$E^*_\gamma $$
E
γ
∗
and
$$cos\Theta ^{*}_{e\gamma }$$
c
o
s
Θ
e
γ
∗
. In particular, the branching ratio for
$$E^{*}_{\gamma }>30$$
E
γ
∗
>
30
MeV and
$$\Theta ^{*}_{e \gamma }>20^{\circ }$$
Θ
e
γ
∗
>
20
∘
is measured R =
$$\frac{Br(K^+ \rightarrow \pi ^{0} e^{+} \nu _{e} \gamma ) }{Br(K^+ \rightarrow \pi ^{0} e^{+} \nu _{e})} $$
B
r
(
K
+
→
π
0
e
+
ν
e
γ
)
B
r
(
K
+
→
π
0
e
+
ν
e
)
= = (0.587±0.010(
stat
.)±0.015(
syst
.))
$$\times 10^{-2}$$
×
10
-
2
, which is in a good agreement with ChPT
$$O(p^{4})$$
O
(
p
4
)
calculations.
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