We search for a light Higgs boson (A^{0}) decaying into a τ^{+}τ^{-} or μ^{+}μ^{-} pair in the radiative decays of ϒ(1S). The production of ϒ(1S) mesons is tagged by ϒ(2S)→π^{+}π^{-}ϒ(1S) ...transitions, using 158×10^{6} ϒ(2S) events accumulated with the Belle detector at the KEKB asymmetric energy electron-positron collider. No significant A^{0} signals in the mass range from the τ^{+}τ^{-} or μ^{+}μ^{-} threshold to 9.2 GeV/c^{2} are observed. We set the upper limits at 90% credibility level (C.L.) on the product branching fractions for ϒ(1S)→γA^{0} and A^{0}→τ^{+}τ^{-} varying from 3.8×10^{-6} to 1.5×10^{-4}. Our results represent an approximately twofold improvement on the current world best upper limits for the ϒ(1S)→γA^{0}(→τ^{+}τ^{-}) production. For A^{0}→μ^{+}μ^{-}, the upper limits on the product branching fractions for ϒ(1S)→γA^{0} and A^{0}→μ^{+}μ^{-} are at the same level as the world average limits, and vary from 3.1×10^{-7} to 1.6×10^{-5}. The upper limits at 90% credibility level on the Yukawa coupling f_{ϒ(1S)} and mixing angle sinθ_{A^{0}} are also given.
We study the processes $e^{+}e^{–} → ωχ_{bJ}$(1P) (J=0, 1, or 2) using samples at center-of-mass energies $\sqrt{s}$ = 10.701, 10.745, and 10.805 GeV, corresponding to 1.6, 9.8, and 4.7 fb–1 of ...integrated luminosity, respectively. These data were collected with the Belle II detector during special operations of the SuperKEKB collider above the Υ(4S) resonance. We report the first observation of $ωχ_{bJ}$(1P) signals at $\sqrt{s}$ = 10.745 GeV. By combining Belle II data with Belle results at $\sqrt{s}$ = 10.867 GeV, we find energy dependencies of the Born cross sections for $e^{+}e^{–} → ωχ_{b1,b2}$(1P) to be consistent with the shape of the Υ(10753) state. These data indicate that the internal structures of the Υ(10753) and Υ(10860) states may differ. Including data at $\sqrt{s}$ = 10.653 GeV, we also search for the bottomonium equivalent of the X(3872) state decaying into ωΥ(1S). No significant signal is observed for masses between 10.45 and 10.65 GeV/c2.
A
bstract
We report the measurement of the two-photon decay width of
χ
c
2
(1
P
) in two-photon processes at the Belle experiment. We analyze the process
γγ
→
χ
c
2
(1
P
) →
J/ψγ
,
J/ψ
→
ℓ
+
ℓ
−
(
ℓ
...=
e
or
μ
) using a data sample of 971 fb
−
1
collected with the Belle detector at the KEKB
e
+
e
−
collider. In this analysis, the product of the two-photon decay width of
χ
c
2
(1
P
) and the branching fraction is determined to be
Γ
γγ
χ
c
2
1
P
B
χ
c
2
1
P
→
J
/
ψγ
B
J
/
ψ
→
ℓ
+
ℓ
−
=
14.8
±
0.3
stat
.
±
0.7
syst
.
eV, which corresponds to Γ
γγ
(
χ
c
2
(1
P
)) = 653
±
13(stat.)
±
31(syst.)
±
17(B.R.) eV, where the third uncertainty is from
B
(
χ
c
2
(1
P
)
→ J/ψγ
) and
B
(
J/ψ → ℓ
+
ℓ
−
).
A
bstract
We present the analysis of two-particle angular correlations using coordinate systems defined with the conventional beam axis and the event thrust axis. We propose the latter as a good ...representation for the correlation structure interpretation in the
e
+
e
−
collision system. The
e
+
e
−
collisions to hadronic final states at center-of-mass energies of
s
= 10
.
52 GeV and 10.58 GeV are recorded by the Belle detector at KEKB. In this paper, results on the first dataset are supplementary to the previous Belle publication
1
. At the same time, the latter is the first two-particle correlation measurement at collision energy on the
Υ
(4
S
) resonance and is sensitive to its decay products. Measurements are reported as a function of the charged-particle multiplicity. Finally, a qualitative understanding of the correlation structure is discussed using a combination of Monte Carlo simulations and experimental data.
A
bstract
We present a measurement of the Cabibbo-Kobayashi-Maskawa unitarity triangle angle
ϕ
3
(also known as
γ
) using a model-independent Dalitz plot analysis of
B
+
→
D
(
K
S
0
h
+
h
−
)
h
+
, ...where
D
is either a
D
0
or
D
¯
0
meson and
h
is either a
π
or
K
. This is the first measurement that simultaneously uses Belle and Belle II data, combining samples corresponding to integrated luminosities of 711 fb
−
1
and 128 fb
−
1
, respectively. All data were accumulated from energy-asymmetric
e
+
e
−
collisions at a centre-of-mass energy corresponding to the mass of the Υ(4
S
) resonance. We measure
ϕ
3
= (78
.
4 ± 11
.
4 ± 0
.
5 ± 1
.
0)°, where the first uncertainty is statistical, the second is the experimental systematic uncertainty and the third is from the uncertainties on external measurements of the
D
-decay strong-phase parameters.
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