A
bstract
We present a search for the charged lepton-flavor-violating decays ϒ(1
S
)
→
ℓ
±
ℓ
′
∓
and radiative charged lepton-flavour-violating decays ϒ(1
S
)
→ γ
ℓ
±
ℓ
′
∓
ℓ
,
ℓ
′ =
e, μ, τ
using ...the 158 million ϒ(2
S
) sample collected by the Belle detector at the KEKB collider. This search uses ϒ(1
S
) mesons produced in ϒ(2
S
)
→ π
+
π
−
ϒ(1
S
) transitions. We do not find any significant signal, so we provide upper limits on the branching fractions at the 90% confidence level.
A
bstract
We measure the cross section of
e
+
e
−
→
η
c
J/ψ
at the Υ(
nS
)(
n
= 1–5) on-resonance and 10.52 GeV off-resonance energy points using the full data sample collected by the Belle detector ...with an integrated luminosity of 955 fb
−
1
. We also search for double charmonium production in
e
+
e
−
→
η
c
J/ψ
via initial state radiation near the
η
c
J/ψ
threshold. No evident signal of the double charmonium state is found, but evidence for the
e
+
e
−
→ η
c
J/ψ
process is found with a statistical significance greater than 3
.
3
σ
near the
η
c
J/ψ
threshold. The average cross section near the threshold is measured and upper limits of cross sections are set for other regions.
Using 980 fb−1 of data collected with the Belle detector operating at the KEKB asymmetric-energy e+ e− collider, we report the measurements of the masses, and the first measurements of the instrinsic ...widths, of the Σc ( 2455 )+ and Σc (2520)+ charmed baryons. We find M (Σc (2455)+) − M (Λc+) = 166.17 ± 0.0 5−0.07+0.16 MeV / c2, Γ (Σc (2455)+) = 2.3 ± 0.3 ± 0.3 MeV /c2, M ( Σc (2520)+) − M(Λc+) = 230.9 ± 0. 5− 0.1+ 0.5 MeV / c2, and Γ(Σc (2520)+) = 17.2− 2.1− 0.7+2.3+3.1 MeV / c2, where the uncertainties are statistical and systematic, respectively. These measurements can be used to test models of the underlying quark structure of the Σc states.
A
bstract
We present a search for the lepton-flavor-violating decays
B
s
0
→
ℓ
∓
τ
±
, where
ℓ
=
e, μ
, using the full data sample of 121 fb
−
1
collected at the Υ(5
S
) resonance with the Belle ...detector at the KEKB asymmetric-energy
e
+
e
−
collider. We use
B
s
0
B
¯
s
0
events in which one
B
s
0
meson is reconstructed in a semileptonic decay mode and the other in the signal mode. We find no evidence for
B
s
0
→ ℓ
∓
τ
±
decays and set upper limits on their branching fractions at 90% confidence level as
B
(
B
s
0
→ e
∓
τ
±
)
<
14
×
10
−
4
and
B
(
B
s
0
→ μ
∓
τ
±
)
<
7
.
3
×
10
−
4
. Our result represents the first upper limit on the
B
s
0
→ e
∓
τ
±
decay rate.
We study the decay B+→K+K– π+ and investigate the angular distribution of K+K– pairs with invariant mass below 1.1 GeV / c2. This region exhibits both a strong enhancement in signal and very large ...direct CP violation. We construct a coherent sum model for the angular distribution of the S- and P-wave, and report the ratio of their amplitudes, the relative phase and the forward-backward asymmetry. We also report absolute differential branching fractions and direct CP asymmetry for the decay in bins of MK+K– and the differential branching fractions in bins of MK+π–. The results are based on a data sample that contains 772 × 106 $B\bar{B}$ pairs collected at the $Υ$(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e– collider. The result favors the presence of S- and D-waves in low MK+K– region to the detriment of a P-wave.
This paper presents a search for the rare flavor-changing neutral current process B0→K*0τ+τ- using data taken with the Belle detector at the KEKB asymmetric energy $e^+$$e^-$ collider. The analysis ...is based on the entire $\Upsilon$$(4S)$ resonance data sample of $711$ $\mathrm{fb}^{-1}$, corresponding to $772 × 10^6$$B$$\bar{B}$ pairs. In our search we fully reconstruct the companion $B$ meson produced in the process $e^+$$e^-$ → $\Upsilon$$(4S)$ → $B$$\bar{B}$ from its hadronic decay modes and look for the decay B0→K*0τ+τ- in the rest of the event. No evidence for a signal is found. We report an upper limit on the branching fraction $\mathscr{B}$(B0→K*0τ+τ-) < $3.1 × 10^{-3}$ at 90% confidence level. This is the first direct limit on $\mathscr{B}$(B0→K*0τ+τ-).
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