Abstract We report evidence for the charged charmed-strange baryon $$\Xi _{c}(2930)^+$$ Ξc(2930)+ with a signal significance of 3.9$$\sigma $$ σ with systematic errors included. The charged $$\Xi ..._{c}(2930)^+$$ Ξc(2930)+ is found in its decay to $$K_{S}^{0} \Lambda _{c}^+$$ KS0Λc+ in the substructure of $$\bar{B}^{0} \rightarrow K^{0}_{S} \Lambda _{c}^{+} \bar{\Lambda }_{c}^{-}$$ B¯0→KS0Λc+Λ¯c- decays. The measured mass and width are $$2942.3 \pm 4.4 ({\mathrm{stat.}}) \pm {1.5}({\mathrm{syst.}})$$ 2942.3±4.4(stat.)±1.5(syst.) MeV/$$c^{2}$$ c2 and $$14.8 \pm 8.8({\mathrm{stat.}}) \pm {2.5}({\mathrm{syst.}})$$ 14.8±8.8(stat.)±2.5(syst.) MeV, respectively, and the product branching fraction is $$\mathcal{B}(\bar{B}^{0} \rightarrow \Xi _c(2930)^{+} \bar{\Lambda }_{c}^{-}) \mathcal{B}(\Xi _c(2930)^{+}\rightarrow \bar{K}^{0} \Lambda _{c}^{+})=2.37 \pm 0.51 ({\mathrm{stat.}})\pm 0.31({\mathrm{syst.}})\times 10^{-4}$$ B(B¯0→Ξc(2930)+Λ¯c-)B(Ξc(2930)+→K¯0Λc+)=2.37±0.51(stat.)±0.31(syst.)×10-4 . We also measure $$\mathcal{B}(\bar{B}^{0} \rightarrow \bar{K}^{0} \Lambda _{c}^{+} \bar{\Lambda }_{c}^{-}) = 3.99 \pm 0.76({\mathrm{stat.}}) \pm 0.51({\mathrm{syst.}}) \times 10^{-4}$$ B(B¯0→K¯0Λc+Λ¯c-)=3.99±0.76(stat.)±0.51(syst.)×10-4 with greater precision than previous experiments, and present the results of a search for the charmonium-like state Y(4660) and its spin partner, $$Y_{\eta }$$ Yη , in the $$\Lambda _{c}^{+}\bar{\Lambda }_{c}^{-}$$ Λc+Λ¯c- invariant mass spectrum. No clear signals of the Y(4660) or $$Y_{\eta }$$ Yη are observed and the 90% credibility level (C.L.) upper limits on their production rates are determined. These measurements are obtained from a sample of $$(772\pm 11)\times 10^{6} B\bar{B}$$ (772±11)×106BB¯ pairs collected at the $$\Upsilon (4S)$$ Υ(4S) resonance by the Belle detector at the KEKB asymmetric energy electron-positron collider.
Abstract We present a search for the lepton-flavor-violating decays B s 0 $$ {B}_s^0 $$ → ℓ ∓ τ ± , where ℓ = e, μ, using the full data sample of 121 fb −1 collected at the Υ(5S) resonance with the ...Belle detector at the KEKB asymmetric-energy e + e − collider. We use B s 0 B ¯ s 0 $$ {B}_s^0{\overline{B}}_s^0 $$ events in which one B s 0 $$ {B}_s^0 $$ meson is reconstructed in a semileptonic decay mode and the other in the signal mode. We find no evidence for B s 0 $$ {B}_s^0 $$ → ℓ ∓ τ ± decays and set upper limits on their branching fractions at 90% confidence level as B $$ \mathcal{B} $$ ( B s 0 $$ {B}_s^0 $$ → e ∓ τ ± ) < 14 × 10 −4 and B $$ \mathcal{B} $$ ( B s 0 $$ {B}_s^0 $$ → μ ∓ τ ± ) < 7.3 × 10 −4. Our result represents the first upper limit on the B s 0 $$ {B}_s^0 $$ → e ∓ τ ± decay rate.
Abstract We report the first measurement of the inclusive e + e − → b b ¯ $$ b\overline{b} $$ → D s ± $$ {D}_s^{\pm } $$ X and e + e − → b b ¯ $$ b\overline{b} $$ → D 0 / D ¯ 0 $$ {\overline{D}}^0 $$ ...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 $$ {B}_s^0{\overline{B}}_s^0 $$ X) and σ(e + e − → B B ¯ $$ B\overline{B} $$ X) in the same energy range. We measure the fraction of B s 0 $$ {B}_s^0 $$ events at Υ(10860) to be f s = ( 22.0 − 2.1 + 2.0 $$ {22.0}_{-2.1}^{+2.0} $$ )%. We determine also the ratio of the B s 0 $$ {B}_s^0 $$ inclusive branching fractions B $$ \mathcal{B} $$ ( B s 0 $$ {B}_s^0 $$ → D 0 / D ¯ 0 $$ {\overline{D}}^0 $$ X)/ B $$ \mathcal{B} $$ ( B s 0 $$ {B}_s^0 $$ → D s ± $$ {D}_s^{\pm } $$ 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.
Abstract We report the first observation of the $$\Xi _{c}(2930)^0$$ Ξc(2930)0 charmed-strange baryon with a significance greater than 5$$\sigma $$ σ . The $$\Xi _{c}(2930)^0$$ Ξc(2930)0 is found in ...its decay to $$K^- \Lambda _{c}^+$$ K-Λc+ in $$B^{-} \rightarrow K^{-} \Lambda _{c}^{+} \bar{\Lambda }_{c}^{-}$$ B-→K-Λc+Λ¯c- decays. The measured mass and width are $$2928.9 \pm 3.0(\mathrm stat.)^{+0.9}_{-12.0}(\mathrm syst.)$$ 2928.9±3.0(stat.)-12.0+0.9(syst.) MeV/$$c^{2}$$ c2 and $$19.5 \pm 8.4(\mathrm stat.) ^{+5.9}_{-7.9}(\mathrm syst.)$$ 19.5±8.4(stat.)-7.9+5.9(syst.) MeV, respectively, and the product branching fraction is $$\mathcal{B}(B^{-} \rightarrow \Xi _{c}(2930)^0 \bar{\Lambda }_{c}^{-}) \mathcal{B}(\Xi _{c}(2930)^0 \rightarrow K^- \Lambda _{c}^{+})=1.73 \pm 0.45(\mathrm stat.) \pm 0.21(\mathrm syst.)\times 10^{-4}$$ B(B-→Ξc(2930)0Λ¯c-)B(Ξc(2930)0→K-Λc+)=1.73±0.45(stat.)±0.21(syst.)×10-4 . We also measure $$\mathcal{B}(B^{-} \rightarrow K^{-} \Lambda _{c}^{+} \bar{\Lambda }_{c}^{-}) = 4.80 \pm 0.43(\mathrm stat.) \pm 0.60(\mathrm syst.) \times 10^{-4}$$ B(B-→K-Λc+Λ¯c-)=4.80±0.43(stat.)±0.60(syst.)×10-4 with improved precision, and search for the charmonium-like state Y(4660) and its spin partner, $$Y_{\eta }$$ Yη , in the $$\Lambda _{c}^{+}\bar{\Lambda }_{c}^{-}$$ Λc+Λ¯c- invariant mass spectrum. No clear signals of the Y(4660) nor its spin partner are observed and the 90% credibility level (C.L.) upper limits on their production rates are determined. These measurements are obtained from a sample of $$(772\pm 11)\times 10^{6} B\bar{B}$$ (772±11)×106BB¯ pairs collected at the $$\Upsilon (4S)$$ Υ(4S) resonance by the Belle detector at the KEKB asymmetric energy electron–positron collider.
Abstract 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 3.3σ 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.
Abstract 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 Ω c 0 → Ξ ...− π + $$ {\Omega}_c^0\to {\Xi}^{-}{\pi}^{+} $$ and Ω − K + and the doubly Cabibbo-suppressed decay Ω c 0 → Ξ − K + $$ {\Omega}_c^0\to {\Xi}^{-}{K}^{+} $$ . Evidence for an Ω c 0 $$ {\Omega}_c^0 $$ signal in the Ω c 0 $$ {\Omega}_c^0 $$ → Ξ − π + mode is reported with a significance of 4.5σ including systematic uncertainties. The ratio of branching fractions to the normalization mode Ω c 0 $$ {\Omega}_c^0 $$ → Ω − π + is measured to be B Ω c 0 → Ξ − π + / B Ω c 0 → Ω − π + = 0.253 ± 0.052 stat . ± 0.030 syst . . $$ \mathcal{B}\left({\Omega}_c^0\to {\Xi}^{-}{\pi}^{+}\right)/\mathcal{B}\left({\Omega}_c^0\to {\Omega}^{-}{\pi}^{+}\right)=0.253\pm 0.052\left(\textrm{stat}.\right)\pm 0.030\left(\textrm{syst}.\right). $$ No significant signals of Ω c 0 → Ξ − K + $$ {\Omega}_c^0\to {\Xi}^{-}{K}^{+} $$ and Ω − K + modes are found. The upper limits at 90% confidence level on ratios of branching fractions are determined to be B Ω c 0 → Ξ − K + / B Ω c 0 → Ω − π + < 0.070 $$ \mathcal{B}\left({\Omega}_c^0\to {\Xi}^{-}{K}^{+}\right)/\mathcal{B}\left({\Omega}_c^0\to {\Omega}^{-}{\pi}^{+}\right)<0.070 $$ and B Ω c 0 → Ω − K + / B Ω c 0 → Ω − π + < 0.29 . $$ \mathcal{B}\left({\Omega}_c^0\to {\Omega}^{-}{K}^{+}\right)/\mathcal{B}\left({\Omega}_c^0\to {\Omega}^{-}{\pi}^{+}\right)<0.29. $$
Abstract 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 $$ {\Xi}_c^0\to \Lambda ...{\overline{K}}^{\ast 0} $$ , Ξ c 0 → Σ 0 K ¯ ∗ 0 $$ {\Xi}_c^0\to {\Sigma}^0{\overline{K}}^{\ast 0} $$ , and Ξ c 0 → Σ + K ∗ − $$ {\Xi}_c^0\to {\Sigma}^{+}{K}^{\ast -} $$ for the first time. The relative branching ratios to the normalization mode of Ξ c 0 → Ξ − π + $$ {\Xi}_c^0\to {\Xi}^{-}{\pi}^{+} $$ 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 . , $$ {\displaystyle \begin{array}{c}\mathcal{B}\left({\Xi}_c^0\to \Lambda {\overline{K}}^{\ast 0}\right)/\mathcal{B}\left({\Xi}_c^0\to {\Xi}^{-}{\pi}^{+}\right)=0.18\pm 0.02\left(\mathrm{stat}.\right)\pm 0.01\left(\mathrm{syst}.\right),\\ {}\mathcal{B}\left({\Xi}_c^0\to {\Sigma}^0{\overline{K}}^{\ast 0}\right)/\mathcal{B}\left({\Xi}_c^0\to {\Xi}^{-}{\pi}^{+}\right)=0.69\pm 0.03\left(\mathrm{stat}.\right)\pm 0.03\left(\mathrm{syst}.\right),\\ {}\mathcal{B}\left({\Xi}_c^0\to {\Sigma}^{+}{K}^{\ast -}\right)/\mathcal{B}\left({\Xi}_c^0\to {\Xi}^{-}{\pi}^{+}\right)=0.34\pm 0.06\left(\mathrm{stat}.\right)\pm 0.02\left(\mathrm{syst}.\right),\end{array}} $$ 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 , $$ {\displaystyle \begin{array}{c}\mathcal{B}\left({\Xi}_c^0\to \Lambda {\overline{K}}^{\ast 0}\right)=\left(3.3\pm 0.3\left(\mathrm{stat}.\right)\pm 0.2\left(\mathrm{syst}.\right)\pm 1.0\left(\mathrm{ref}.\right)\right)\times {10}^{-3},\\ {}\mathcal{B}\left({\Xi}_c^0\to {\Sigma}^0{\overline{K}}^{\ast 0}\right)=\left(12.4\pm 0.5\left(\mathrm{stat}.\right)\pm 0.5\left(\mathrm{syst}.\right)\pm 3.6\left(\mathrm{ref}.\right)\right)\times {10}^{-3},\\ {}\mathcal{B}\left({\Xi}_c^0\to {\Sigma}^{+}{K}^{\ast 0}\right)=\left(6.1\pm 1.0\left(\mathrm{stat}.\right)\pm 0.4\left(\mathrm{syst}.\right)\pm 1.8\left(\mathrm{ref}.\right)\right)\times {10}^{-3},\end{array}} $$ where the uncertainties are statistical, systematic, and from B Ξ c 0 → Ξ − π + $$ \mathcal{B}\left({\Xi}_c^0\to {\Xi}^{-}{\pi}^{+}\right) $$ , respectively. The asymmetry parameters α Ξ c 0 → Λ K ¯ ∗ 0 $$ \alpha \left({\Xi}_c^0\to \Lambda {\overline{K}}^{\ast 0}\right) $$ and α Ξ c 0 → Σ + K ∗ − $$ \alpha \left({\Xi}_c^0\to {\Sigma}^{+}{K}^{\ast -}\right) $$ 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.
We report measurements of differential cross sections and decay asymmetries of incoherent
ϕ-meson photoproduction from the deuteron at forward angles using linearly polarized photons at
E
γ
=
1.5
–
...2.4
GeV
. The nuclear transparency ratio for the deuteron shows a large suppression, and is consistent with the A-dependence of the ratio observed in a previous measurement with nuclear targets. The reduction for the deuteron cannot be adequately explained in term of isospin asymmetry. The present results suggest the need of refining our understanding of the
ϕ–N interaction within a nucleus.
We measured missing mass spectrum of the ^{12}C(γ,p) reaction for the first time in coincidence with potential decay products from η^{'} bound nuclei. We tagged an (η+p) pair associated with the ...η^{'}N→ηN process in a nucleus. After applying kinematical selections to reduce backgrounds, no signal events were observed in the bound-state region. An upper limit of the signal cross section in the opening angle cosθ_{lab}^{ηp}<-0.9 was obtained to be 2.2 nb/sr at the 90% confidence level. It is compared with theoretical cross sections, whose normalization ambiguity is suppressed by measuring a quasifree η^{'} production rate. Our results indicate a small branching fraction of the η^{'}N→ηN process and/or a shallow η^{'}-nucleus potential.
Differential cross sections and decay asymmetries for coherent ϕ-meson photoproduction from deuterons were measured for the first time at forward angles using linearly polarized photons at ...Eγ=1.5–2.4 GeV. This reaction offers a unique way to directly access natural-parity pomeron dynamics and gluon exchange at low energies. The cross sections at zero degrees increase with increasing photon energy. The decay asymmetries demonstrate a complete dominance of natural-parity exchange processes, showing that isovector unnatural-parity π-meson exchange is small. Nevertheless the deduced cross sections of ϕ-mesons from nucleons contributed by isoscalar t-channel exchange processes are not well described by the conventional pomeron model.
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