Phys. Rev. D 102, 112001 (2020) We report the results of a first search for a doubly-charged $DDK$ bound
state, denoted the $R^{++}$, in $\Upsilon(1S)$ and $\Upsilon(2S)$ inclusive
decays and via ...direct production in $e^+e^-$ collisions at $\sqrt{s}$ = 10.520,
10.580, and 10.867 GeV. The search uses data accumulated with the Belle
detector at the KEKB asymmetric-energy $e^+e^-$ collider. No significant
signals are observed in the $D^{+}D_{s}^{*+}$ invariant-mass spectra of all
studied modes. The 90\% credibility level upper limits on their product
branching fractions in $\Upsilon(1S)$ and $\Upsilon(2S)$ inclusive decays
(${\cal B}(\Upsilon(1S,2S) \to R^{++} + anything) \times {\cal B}(R^{++} \to
D^{+} D_{s}^{*+})$), and the product values of Born cross section and branching
fraction in $e^+e^-$ collisions ($\sigma(e^+e^- \to R^{++} + anything) \times
{\cal B}(R^{++} \to D^{+} D_{s}^{*+})$) at $\sqrt{s}$ = 10.520, 10.580, and
10.867 GeV under different assumptions of $R^{++}$ masses varying from 4.13 to
4.17 GeV/$c^2$, and widths varying from 0 to 5 MeV are obtained.
Phys. Rev. D 103, 052005 (2021) We report branching fraction measurements of four decay modes of the
$\Lambda_{c}^{+}$ baryon, each of which includes an $\eta$ meson and a
$\Lambda$ baryon in the ...final state, and all of which are measured relative to
the $\Lambda_{c}^{+} \rightarrow p K^{-} pi^{+}$ decay mode.
The results are based on a $980~\mathrm{fb^{-1}}$ data sample collected by
the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider.
Two decays, $\eta \Sigma^{0} \pi^{+}$ and $\Lambda(1670) \pi^{+}$, are
observed for the first time, while the measurements of the other decay modes,
$\Lambda_{c}^{+} \rightarrow \eta\Lambda\pi^{+}$ and $\eta\Sigma(1385)^{+}$,
are more precise than those made previously.
We obtain $\mathcal{B}(\Lambda_{c}^{+} \rightarrow \eta \Lambda
\pi^{+})/\mathcal{B}(\Lambda_{c}^{+} \rightarrow p K^{-} \pi^{+})$ = $0.293 \pm
0.003 \pm 0.014$, $\mathcal{B}(\Lambda_{c}^{+} \rightarrow \eta \Sigma^{0}
\pi^{+})/\mathcal{B}(\Lambda_{c}^{+} \rightarrow p K^{-} \pi^{+})$ = $0.120 \pm
0.006 \pm 0.006$, $\mathcal{B}(\Lambda_{c}^{+} \rightarrow \Lambda(1670)
\pi^{+}) \times \mathcal{B}(\Lambda(1670) \rightarrow \eta
\Lambda)/\mathcal{B}(\Lambda_{c}^{+} \rightarrow p K^{-} \pi^{+})$ = $(5.54 \pm
0.29 \pm 0.73 ) \times 10^{-2}$, and $\mathcal{B}(\Lambda_{c}^{+} \rightarrow
\eta \Sigma(1385)^{+})/\mathcal{B}(\Lambda_{c}^{+} \rightarrow p K^{-}
\pi^{+})$ = $0.192 \pm 0.006 \pm 0.016$.
The mass and width of the $\Lambda(1670)$ are also precisely determined to be
$1674.3 \pm 0.8 \pm 4.9~{\rm MeV}/c^{2}$ and $36.1 \pm 2.4 \pm 4.8~{\rm MeV}$,
respectively, where the uncertainties are statistical and systematic,
respectively.
Phys. Rev. D 102, 012003 (2020) We report searches for $B^0\to\rm{invisible}$ and
$B^0\to\rm{invisible}+\gamma$ decays, where the energy of the photon is
required to be larger than 0.5 GeV. These ...results are obtained from a
$711\,{\rm fb}^{-1}$ data sample that contains $772 \times 10^6 B\bar{B}$ pairs
and was collected near the $\Upsilon\,(4S)$ resonance with the Belle detector
at the KEKB $e^+ e^-$ collider. We observe no significant signal for either
decay and set upper limits on their branching fractions at $90\%$ confidence
level of $\mathcal{B}\,(B^0\to\rm{invisible}) < 7.8\times10^{-5}$ and
$\mathcal{B}\,(B^0\to\rm{invisible}+\gamma) < 1.6\times10^{-5}$.
Phys. Rev. D 103, 112001 (2021) We present an analysis of the exclusive
$B^{+}\to\pi^{+}\pi^{-}\ell^{+}\nu_{\ell}$ decay, where $\ell$ represents an
electron or a muon, with the assumption of ...charge-conjugation symmetry and
lepton universality. The analysis uses the full $\Upsilon(4S)$ data sample
collected by the Belle detector, corresponding to 711 fb$^{-1}$ of integrated
luminosity. We select the events by fully reconstructing one $B$ meson in
hadronic decay modes, subsequently determining the properties of the other $B$
meson. We extract the signal yields using a binned maximum-likelihood fit to
the missing-mass squared distribution in bins of the invariant mass of the two
pions or the momentum transfer squared. We measure a total branching fraction
of ${{\cal B}(B^{+}\to \pi^{+}\pi^{-}\ell^{+}\nu_{\ell})= 22.7 ^{+1.9}_{-1.6}
(\mathrm{stat}) \pm 3.5(\mathrm{syst}) \times 10^{-5}}$, where the
uncertainties are statistical and systematic, respectively. This result is the
first reported measurement of this decay.
Phys. Rev. D 101, 091101 (2020) We report the measurement of $e^+e^- \to D^+_sD^*_{s2}(2573)^-+c.c.$ via
initial-state radiation using a data sample of an integrated luminosity of
921.9 fb$^{-1}$ ...collected with the Belle detector at the $\Upsilon(4S)$ and
nearby. We find evidence for an enhancement with a 3.4$\sigma$ significance in
the invariant mass of $D^+_sD^*_{s2}(2573)^- +c.c.$ The measured mass and width
are $(4619.8^{+8.9}_{-8.0}({\rm stat.})\pm2.3({\rm syst.}))~{\rm MeV}/c^{2}$
and $(47.0^{+31.3}_{-14.8}({\rm stat.})\pm4.6({\rm syst.}))~{\rm MeV}$,
respectively. The mass, width, and quantum numbers of this enhancement are
consistent with the charmonium-like state at 4626 MeV/$c^2$ recently reported
by Belle in $e^+e^-\to D^+_sD_{s1}(2536)^-+c.c.$ The product of the $e^+e^-\to
D^+_sD^*_{s2}(2573)^-+c.c.$ cross section and the branching fraction of
$D^*_{s2}(2573)^-\to{\bar D}^0K^-$ is measured from $D^+_sD^*_{s2}(2573)^-$
threshold to 5.6 GeV.
JHEP 05 (2020) 034 The first dedicated search for the $\eta_{c2}(1D)$ is carried out using the
decays $B^+ \rightarrow \eta_{c2}(1D) K^+$, $B^0 \rightarrow \eta_{c2}(1D)
K^0_S$, $B^0 \rightarrow ...\eta_{c2}(1D) \pi^- K^+$, and $B^+ \rightarrow
\eta_{c2}(1D) \pi^+ K^0_S$ with $\eta_{c2}(1D) \to h_c \gamma$. No significant
signal is found. For the $\eta_{c2}(1D)$ mass range between $3795$ and $3845\
\mathrm{MeV}/c^2$, the branching-fraction upper limits are determined to be
$\mathcal{B}(B^+ \rightarrow \eta_{c2}(1D) K^+) \times
\mathcal{B}(\eta_{c2}(1D) \to h_c \gamma) < 3.7 \times 10^{-5}$,
$\mathcal{B}(B^0 \rightarrow \eta_{c2}(1D) K^0_S) \times
\mathcal{B}(\eta_{c2}(1D) \to h_c \gamma) < 3.5 \times 10^{-5}$,
$\mathcal{B}(B^0 \rightarrow \eta_{c2}(1D) \pi^- K^+) \times
\mathcal{B}(\eta_{c2}(1D) \to h_c \gamma) < 1.0 \times 10^{-4}$, and
$\mathcal{B}(B^+ \rightarrow \eta_{c2}(1D) \pi^+ K^0_S) \times
\mathcal{B}(\eta_{c2}(1D) \to h_c \gamma) < 1.1 \times 10^{-4}$ at 90% C. L.
The analysis is based on the 711 $\mathrm{fb}^{-1}$ data sample collected on
the $\Upsilon(4S)$ resonance by the Belle detector, which operated at the KEKB
asymmetric-energy $e^+ e^-$ collider.
Phys. Rev. D 102, 012002 (2020) We present the results of the first Dalitz plot analysis of the decay
$D^{0}\to K^{-}\pi^{+}\eta$. The analysis is performed on a data set
corresponding to an ...integrated luminosity of 953 $\rm{fb}^{-1}$ collected by
the Belle detector at the asymmetric-energy $e^{+}e^{-}$ KEKB collider. The
Dalitz plot is well described by a combination of the six resonant decay
channels $\bar{K}^{*}(892)^0\eta$, $K^{-}a_0(980)^+$, $K^{-}a_2(1320)^+$,
$\bar{K}^{*}(1410)^0\eta$, $K^{*}(1680)^-\pi^{+}$ and $K_2^{*}(1980)^-\pi^{+}$,
together with $K\pi$ and $K\eta$ S-wave components. The decays
$K^{*}(1680)^{-}\to K^{-}\eta$ and $K_{2}^{*}(1980)^{-}\to K^{-}\eta$ are
observed for the first time. We measure ratio of the branching fractions,
$\frac{\mathcal{B}(D^{0}\to K^{-}\pi^{+}\eta)}{\mathcal{B}(D^{0}\to
K^{-}\pi^{+})}=0.500\pm0.002{\rm(stat)}\pm0.020{\rm(syst)}\pm0.003{\rm
(\mathcal{B}_{PDG})}$. Using the Dalitz fit result, the ratio
$\frac{\mathcal{B}(K^{*}(1680)\to K\eta)}{\mathcal{B}(K^{*}(1680)\to K\pi)}$ is
measured to be
$0.11\pm0.02{\rm(stat)}^{+0.06}_{-0.04}{\rm(syst)}\pm0.04{\rm(\mathcal{B}_{\text{PDG}})}$;
this is much lower than the theoretical expectations ($\approx1$) made under
the assumption that $K^{*}(1680)$ is a pure $1^{3}D_1$ state. The product
branching fraction $\mathcal{B}(D^0\to K_2^{*}(1980)^-\to
K^{-}\eta\pi^{+})=(2.2^{+1.7}_{-1.9})\times10^{-4}$ is determined. In
addition, the $\pi\eta^{\prime}$ contribution to the $a_0(980)^{\pm}$ resonance
shape is confirmed with 10.1$\sigma$ statistical significance using the
three-channel Flatt\'{e} model. We also measure
$\mathcal{B}(D^0\to\bar{K}^{*}(892)^0\eta)=(1.41^{+0.13}_{-0.12})\%$. This is
consistent with, and more precise than, the current world average
$(1.02\pm0.30)\%$, deviates with a significance of more than $3\sigma$ from the
theoretical predictions of (0.51-0.92)%.
Phys. Rev. D 101, 052012 (2020) Using a data sample of $772 \times 10^6$ BB pairs collected on the
${\Upsilon}(4S)$ resonance with the Belle detector at the KEKB
asymmetric-energy $e^+e^-$ collider, ...we report the observations of $B^0\to
p{\bar p}\pi^+\pi^-$ and $B^+ \to p{\bar p}\pi^+\pi^0$. We measure a decay
branching fraction of $(0.83 \pm 0.17 \pm 0.17) \times 10^-6$ in $B^0\to p{\bar
p}\pi^+\pi^-$ for $M_{\pi^+\pi^-} < 1.22 GeV/c^2$ with a significance of 5.5
standard deviations. The contribution from $B0 \to p{\bar p}K^0$ is excluded.
We measure a decay branching fraction of $(4.58 \pm 1.17 \pm 0.67) \times
10^-6$ for $B^+ \to p{\bar p}\pi^+\pi^0$ with $M_{\pi^+\pi^0} < 1.3 GeV/c^2$
with a significance of 5.4 standard deviations. We study the difference of the
$M_{p{\bar p}}$ distributions in $B^0\to p{\bar p}\pi^+\pi^-$ and $B^+ \to
p{\bar p}\pi^+\pi^0$.
Phys. Rev. D 100, 111103 (2019) Using a data sample of 921.9 fb$^{-1}$ collected with the Belle detector, we
study the process of $e^+e^-\to D^+_sD_{s1}(2536)^-+c.c.$ via initial-state
radiation. We ...report the first observation of a vector charmoniumlike state
decaying to $D^+_sD_{s1}(2536)^-+c.c.$ with a significance of 5.9$\sigma$,
including the systematic uncertainties. The measured mass and width are
$(4625.9^{+6.2}_{-6.0}({\rm stat.})\pm0.4({\rm syst.}))~{\rm MeV}/c^{2}$ and
$(49.8^{+13.9}_{-11.5}({\rm stat.})\pm4.0({\rm syst.}))~{\rm MeV}$,
respectively. The product of the $e^+e^-\to D^+_sD_{s1}(2536)^-+c.c.$ cross
section and the branching fraction of $D_{s1}(2536)^-\to{\bar D}^{*0}K^-$ is
measured from the $D_s \bar{D}_{s1}(2536)$ threshold to 5.59~GeV.
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