A search for the decays $B^+ \rightarrow h_c K^+$ and $B^0 \rightarrow h_c K_S^0$ is performed. Evidence for the decay $B^+ \rightarrow h_c K^+$ is found; its significance is $4.8\sigma$. No evidence ...is found for $B^0 \rightarrow h_c K_S^0$. The branching fraction for $B^+ \rightarrow h_c K^+$ is measured to be $(3.7^{+1.0}_{-0.9}{}^{+0.8}_{-0.8}) \times 10^{-5}$; the upper limit for the $B^0 \rightarrow h_c K_S^0$ branching fraction is $1.4 \times 10^{-5}$ at $90\%$ C.L. In addition, a study of the $p \bar{p} \pi^+ \pi^-$ invariant mass distribution in the channel $B^+ \to (p \bar{p} \pi^+ \pi^-) K^+$ results in the first observation of the decay $\eta_c(2S) \to p \bar{p} \pi^+ \pi^-$ with $12.1\sigma$ significance. The analysis is based on the 711 $\mathrm{fb}^{-1}$ data sample collected by the Belle detector at the asymmetric-energy $e^+ e^-$ collider KEKB at the $\Upsilon(4S)$ resonance.
We report the results of a search for the $B → Y(4260)K, Y(4260) → J/ψπ^+π^−$ decays. This study is based on a data sample corresponding to an integrated luminosity of $711 fb^{−1}$, collected at the ...$Υ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^−$ collider. We investigate the $J/ψπ^+π^−$ invariant mass distribution in the range 4.0 to 4.6 $GeV/c^2$ using both $B^+ → J/ψπ^+π^− K^+$ and $B^0 → J/ψπ^+π^− K^0_S$ decays. We find excesses of events above the background levels, with a significances of 2.1 and 0.9 standard deviations for charged and neutral $B → Y(4260)K$ decays, respectively, taking into account the systematic uncertainties. These correspond to upper limits on the product of branching fractions, $\mathcal{B}(B^+ → Y(4260)K^+) × \mathcal{B}(Y(4260) → J/ψπ^+π^−) < 1.4 × 10^{−5}$ and $\mathcal{B}(B^0 → Y(4260)K^0) × \mathcal{B}(Y(4260) → J/ψπ^+π^−) < 1.7 × 10^{−5}$ at the 90\% confidence level.
We present the first model-independent measurement of the CKM unitarity triangle angle ϕ3 using B±→ D(K0Sπ+π−π0) K± decays, where D indicates either a D0 or D¯¯¯¯0 meson. Measurements of the ...strong-phase difference of the D →K0Sπ+π−π0 amplitude obtained from CLEO-c data are used as input. This analysis is based on the full Belle data set of 772 × 106BB¯¯¯¯ events collected at the Υ(4S) resonance. We obtain ϕ3 = (5.7+10.2−8.8±3.5±5.7)° and the suppressed amplitude ratio rB = 0.323±0.147±0.023±0.051. Here the first uncertainty is statistical, the second is the experimental systematic, and the third is due to the precision of the strong-phase parameters measured from CLEO-c data. The 95% confidence interval on ϕ3 is (−29.7, 109.5)°, which is consistent with the current world average.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This work reports the first observation of azimuthal asymmetries around the thrust axis in e+e− annihilation of pairs of back-to-back charged pions in one hemisphere, and π0 and η mesons in the ...opposite hemisphere. These results are complemented by a new analysis of pairs of back-to-back charged pions. The π0 and η asymmetries rise with the relative momentum z of the detected hadrons as well as with the transverse momentum with respect to the thrust axis. These asymmetries are sensitive to the Collins fragmentation function H⊥1 and provide complementary information to previous measurements with charged pions and kaons in the final state. In particular, the η final states will provide additional information on the flavor structure of H⊥1. This is the first measurement of the explicit transverse-momentum dependence of the Collins fragmentation function from Belle data. It uses a dataset of 980.4 fb−1 collected by the Belle experiment at or near a center-of-mass energy of 10.58 GeV.
We present the first measurements of branching fractions of rare tau-lepton decays, τ-→π-ντℓ+ℓ- (ℓ=e or μ), using a data sample corresponding to 562 fb-1 collected at a center-of-mass energy of 10.58 ...GeV with the Belle detector at the KEKB asymmetric-energy e+e- collider. The τ-→π-ντe+e- decay is observed for the first time with 7.0σ significance. The partial branching fraction determined by the structure-dependent mechanisms mediated by either a vector or an axial-vector current for the mass region Mπee>1.05 GeV/c2 is measured to be B(τ-→π-ντe+e-)Mπ-e+e->1.05 GeV/c2=(5.90±0.53±0.85±0.11)×10-6, where the first uncertainty is statistical, the second is systematic, and the third is due to model dependence. In the full phase space, due to the different detection efficiencies for the structure-dependent mechanisms mediated by axial-vector and vector currents, the branching fraction varies from BA(τ-→π-ντe+e-)=(1.46±0.13±0.21)×10-5 to BV(τ-→π-ντe+e-)=(3.01±0.27±0.43)×10-5, respectively. An upper limit is set on the branching fraction of the τ-→π-ντμ+μ- decay, B(τ-→π-ντμ+μ-)<1.14×10-5, at the 90% confidence level.
We study charmless hadronic decays of charged B mesons to the final states $K_{S}^{0}K_{S}^{0}K^±$ and $K_{S}^{0}K_{S}^{0}π^±$ using a 711 fb$^{-1}$ data sample that contains 772×10$^6$ $B\bar{B}$ ...pairs and was collected at the $ϒ(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. For $B^± → K_{S}^{0}K_{S}^{0}K^±$, the measured branching fraction and direct CP asymmetry are $10.42±0.43(stat)±0.22(syst) × 10^{-6 }$ and $+1.6±3.9(stat)±0.9(syst)\%$, respectively. In the absence of a statistically significant signal for $B^± → K_{S}^{0}K_{S}^{0}K^±$, we obtain a 90% confidence-level upper limit on its branching fraction as $8.7 × 10^{-7}$.
We present the first measurements of the absolute branching fractions of $\Xi_c^+$ decays into $\Xi^- \pi^+ \pi^+$, $p K^- \pi^+$, and $p \bar{K}^{*}(892)^{0}$ final states. Our analysis is based on ...a data set of $(772\pm 11)\times 10^{6}$ $B\bar{B}$ pairs collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB $e^+e^-$ collider. We measure the absolute branching fraction of $\bar{B}^{0} \to \bar{\Lambda}_{c}^{-} \Xi_{c}^{+}$ with the $\Xi_c^+$ signal recoiling against $\bar{\Lambda}_c^-$ in $\bar{B}^0$ decays resulting in ${\cal B}(\bar{B}^{0} \to \bar{\Lambda}_{c}^{-} \Xi_{c}^{+}) = 1.16 \pm 0.42(\rm stat.) \pm 0.15(\rm syst.) \times 10^{-3}$. We then measure the product branching fractions ${\cal B}(\bar{B}^{0} \to \bar{\Lambda}_c^- \Xi_c^+){\cal B}(\Xi_c^+ \to \Xi^- \pi^+ \pi^+)$, ${\cal B}(\bar{B}^{0} \to \bar{\Lambda}_c^- \Xi_c^+){\cal B}(\Xi_c^+ \to p K^- \pi^+)$, and ${\cal B}(\bar{B}^{0} \to \bar{\Lambda}_c^- \Xi_c^+){\cal B}(\Xi_c^+ \to p \bar{K}^{*}(892)^{0})$. Dividing these product branching fractions by $\bar{B}^{0} \to \bar{\Lambda}_{c}^{-} \Xi_{c}^{+}$ yields: ${\cal B}(\Xi_c^+ \to \Xi^- \pi^+ \pi^+) = 2.86 \pm 1.21(\rm stat.) \pm 0.38(\rm syst.)\%$, ${\cal B}(\Xi_c^+ \to p K^- \pi^+)=0.45 \pm 0.21(\rm stat.) \pm 0.07(\rm syst.)\%$, and ${\cal B}(\Xi_c^+ \to p \bar{K}^{*}(892)^{0}) = 0.25 \pm 0.16(\rm stat.) \pm 0.04(\rm syst.)\%$. Our result for ${\cal B}(\Xi_c^+ \to \Xi^- \pi^+ \pi^+)$ can be combined with $\Xi_c^+$ branching fractions measured relative to $\Xi_c^+ \to \Xi^- \pi^+ \pi^+$ to set the absolute scale for many $\Xi_c^+$ branching fractions.
We report the results of a search for the decay $B^0 → X(3872)(→ J/ψ π^+ π^−)γ$. The analysis is performed on a data sample corresponding to an integrated luminosity of 711fb$^{−1}$ and containing ...$772 \times 10^6 B\bar{B}$ pairs, collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^−$ collider running at the $Υ(4S)$ resonance energy. We find no evidence for a signal and place an upper limit of $\mathcal{B}(B^0 → X(3872)γ) \times \mathcal{B}(X(3872) → J/ψ π^+ π^−) < 5.1 \times 10^{−7}$ at 90% confidence level.
We report a search for $X(3872)$ and $X(3915)$ in $B^+ \to \chi_{c1} \pi^0 K^+$ decays. We set an upper limit of $\mathcal{B}(B^+ \to X(3872) K^+) \times \mathcal{B}(X(3872) \to \chi_{c1} \pi^0)$ $ < ...8.1 \times 10^{-6}$ and $\mathcal{B}(B^+ \to X(3915) K^+) \times \mathcal{B}(X(3915) \to \chi_{c1} \pi^0)$ $ < 3.8 \times 10^{-5}$ at 90\% confidence level. We also measure $\mathcal{B}(X(3872) \to \chi_{c1} \pi^0)/\mathcal{B}(X(3872) \to J/\psi \pi^+ \pi^-) < 0.97$ at 90\% confidence level. The results reported here are obtained from $772 \times 10^{6}$ $B\overline{B}$ events collected at the $\Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider.
Using data samples of 89.5 fb$^{−1}$, 711.0 fb$^{−1}$, and 121.4 fb$^{−1}$ collected with the Belle detector at the KEKB asymmetric-energy $e^+e^−$ collider at center-of-mass energies 10.52, ...10.58, and 10.867 GeV, respectively, we study the exclusive reactions $e^+ e^− →γχ_{cJ}$ (J=0, 1, 2) and $e^+ e^− →γη_c$. A significant $γχ_{c1}$ signal is observed for the first time at $√s$=10.58 GeV with a significance of 5.1$σ$ including systematic uncertainties. No significant excesses for $γχ_{c0}, γχ_{c2}$, and $γη_c$ final states are found, and we set 90% credibility level upper limits on the Born cross sections $(σB)$ at 10.52 GeV, 10.58 GeV, and 10.867 GeV. Together with cross sections measured by BESIII at lower center-of-mass energies, the energy dependency of $σ_B(e^+e^− → γχ_{c1})$ is obtained.
