We present a study of rare decay modes \(B^{+} \to D_{s}^{+}h^{0}\), \(B^{+} \to D_{s}^{\ast+}h^{0}\), and \(B^{+} \to D^{+}h^{0}\), where \(h^{0}\) denotes the neutral mesons \(\eta\) or \(K^{0}\), ...using a data sample of \((772 \pm 10 ) \times 10^{6}\) \(B\bar{B}\) events produced at the \(\Upsilon(4S)\) resonance. The data were collected by the Belle detector operating at the asymmetric-energy KEKB collider. We observe no evidence for these decays, so we provide upper limits at the 90\(\%\) confidence level on the branching fractions of \(B^{+} \to D_{s}^{+}h^{0}\), \(D_{s}^{\ast+}h^{0}\), and \(D^{+}h^{0}\) decay modes. Along with rare decay modes, we report improved measurements of the color-suppressed decay branching fractions \(\mathcal{B}(\bar{B}^{0} \to D^{0}\eta)\) = (26.6 \(\pm\) 1.2 \(\pm\) 2.1) \(\times\) \(10^{-5}\) and \(\mathcal{B}(\bar{B}^{0} \to D^{0}\bar{K}^{0})\) = (5.6 \(\pm\) 0.5 \(\pm\) 0.2) \(\times\) \(10^{-5}\). The first and second uncertainties are statistical and systematic, respectively.
We present a study of a singly Cabibbo-suppressed decay \(\Lambda_c^+\to{}pK_S^0K_S^0\) and a Cabibbo-favored decay \(\Lambda_c^+\to{}pK_S^0\eta\) based on 980 \(\rm fb^{-1}\) of data collected by ...the Belle detector, operating at the KEKB energy-asymmetric \(e^+e^-\) collider. We measure their branching fractions relative to \(\Lambda_c^+\to{}pK_S^0\): \(\mathcal{B}(\Lambda_c^+\to{}pK_S^0K_S^0)/\mathcal{B}(\Lambda_c^+\to{}pK_S^0)={(1.48 \pm 0.08 \pm 0.04)\times 10^{-2}}\) and \(\mathcal{B}(\Lambda_c^+\to{}pK_S^0\eta)/\mathcal{B}(\Lambda_c^+\to{}pK_S^0)={(2.73\pm 0.06\pm 0.13)\times 10^{-1}}\). Combining with the world average \(\mathcal{B}(\Lambda_c^+\to{}pK_S^0)\), we have the absolute branching fractions: \(\mathcal{B}(\Lambda_c^+\to{}pK_S^0K_S^0) = {(2.35\pm 0.12\pm 0.07 \pm 0.12 )\times 10^{-4}}\) and \(\mathcal{B}(\Lambda_c^+\to{}pK_S^0\eta) = {(4.35\pm 0.10\pm 0.20 \pm 0.22 )\times 10^{-3}}\). The first and second uncertainties are statistical and systematic, respectively, while the third ones arise from the uncertainty on \(\mathcal{B}(\Lambda_c^+\to{}pK_S^0)\). The mode \(\Lambda_c^+\to{}pK_S^0K_S^0\) is observed for the first time and has a statistical significance of \(>\!10\sigma\). The branching fraction of \(\Lambda_c^+\to{}pK_S^0\eta\) has been measured with a threefold improvement in precision over previous results and is found to be consistent with the world average.
We present a search for the decay \(X(3872) \to \pi^+\pi^-\pi^0\) in the \((772\pm11)\times10^6\) \(\Upsilon(4S)\to B \bar B\) data sample collected at the Belle detector, where the \(X(3872)\) is ...produced in \(B^{\pm}\to K^{\pm}X(3872)\) and \(B^{0}\to K_{S}^0 X(3872)\) decays. We do not observe a signal, and set 90\% credible upper limits for two different models of the decay processes: if the decay products are distributed uniformly in phase space, \(\mathcal{B}(X(3872) \to \pi^+\pi^-\pi^0) < 1.3\%\); if \(M(\pi^+\pi^-)\) is concentrated near the mass of the \(D^0 \bar D^0\) pair in the process \(X(3872)\to D^0\bar{D}^{*0}+c.c.\to D^0 \bar D^{0}\pi^0\to\pi^+ \pi^- \pi^0\), \(\mathcal{B}(X(3872) \to \pi^+\pi^-\pi^0) < 1.2\times10^{-3}\).
We report the results of the first search for the decay \(B_s^0\rightarrow\pi^0\pi^0\) using \(121.4\ \rm fb^{-1}\) of data collected at the \(\Upsilon(5\rm S)\) resonance with the Belle detector at ...the KEKB asymmetric-energy \(e^+e^-\) collider. We observe no signal and set a 90\% confidence level upper limit of \(7.7\times 10^{-6}\) on the \(B_s^0\rightarrow\pi^0\pi^0\) decay branching fraction.
We report the measurement of the two-photon decay width of \(\chi_{c2}(1P)\) in two-photon processes at the Belle experiment. We analyze the process \( \gamma \gamma \rightarrow \chi_{c2}(1P) ...\rightarrow J/\psi\gamma\), \(J/\psi \rightarrow \ell^{+} \ell^{-}\) \((\ell = e \ {\rm or} \ \mu)\) 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 \(\chi_{c2}(1P)\) and the branching fraction is determined to be \(\Gamma_{\gamma \gamma}(\chi_{c2}(1P)) \mathcal{B}( \chi_{c2}(1P) \rightarrow J/\psi \, \gamma )\mathcal{B}( J/\psi \rightarrow \ell^+\ell^- ) = {\rm 14.8}\) \(\pm\) \({\rm 0.3}({\rm stat.})\) \(\pm\) \({\rm 0.7}({\rm syst.})\) eV, which corresponds to \( \Gamma_{\gamma \gamma}(\chi_{c2}(1P)) \) = 653 \(\pm\) 13(stat.) \(\pm\) 31(syst.) \(\pm\) 17(B.R.) eV, where the third uncertainty is from \(\mathcal{B}( \chi_{c2}(1P) \rightarrow J/\psi \, \gamma )\) and \(\mathcal{B}( J/\psi \rightarrow \ell^+\ell^- )\).
We report measurements of the ratios of branching fractions for \(B \to \bar{D}^{(*)}\pi\ell^+\nu_\ell\) and \(B \to \bar{D}^{(*)}\pi^+\pi^-\ell^+\nu_\ell\) relative to \(B \to ...\bar{D}^*\ell^+\nu_\ell\) decays with \(\ell = e, \mu\). These results are obtained from a data sample that contains \(772 \times 10^6 B\bar{B}\) pairs collected near the \(\Upsilon(4S)\) resonance with the Belle detector at the KEKB asymmetric energy \(e^+e^-\) collider. Fully reconstructing both \(B\) mesons in the event, we obtain \begin{align*} \frac{B(B^0 \to \bar{D}^0\pi^-\ell^+\nu_\ell)}{B(B^0 \to D^{*-}\ell^+\nu_\ell)} &= (7.24\pm0.36\pm0.12)\%\ ,\\ \frac{B(B^+ \to D^-\pi^+\ell^+\nu_\ell)}{B(B^+ \to \bar{D}^{*0}\ell^+\nu_\ell)} &= (6.78\pm0.24\pm0.15)\%\ ,\\ \frac{B(B^0 \to \bar{D}^{*0}\pi^-\ell^+\nu_\ell)}{B(B^0 \to D^{*-}\ell^+\nu_\ell)} &= (11.10\pm0.48\pm0.20)\%\ ,\\ \frac{B(B^+ \to D^{*-}\pi^+\ell^+\nu_\ell)}{B(B^+ \to \bar{D}^{*0}\ell^+\nu_\ell)} &= (9.50\pm0.33\pm0.27)\%\ ,\\ \frac{B(B^0 \to D^-\pi^+\pi^-\ell^+\nu_\ell)}{B(B^0 \to D^{*-}\ell^+\nu_\ell)} &= (2.91\pm0.37\pm0.25)\%\ ,\\ \frac{B(B^+ \to \bar{D}^0\pi^+\pi^-\ell^+\nu_\ell)}{B(B^+ \to \bar{D}^{*0}\ell^+\nu_\ell)} &= (3.10\pm0.26\pm0.21)\%\ ,\\ \frac{B(B^0 \to D^{*-}\pi^+\pi^-\ell^+\nu_\ell)}{B(B^0 \to D^{*-}\ell^+\nu_\ell)} &= (1.03\pm0.43\pm0.18)\%\ ,\\ \frac{B(B^+ \to \bar{D}^{*0}\pi^+\pi^-\ell^+\nu_\ell)}{B(B^+ \to \bar{D}^{*0}\ell^+\nu_\ell)} &= (1.25\pm0.27\pm0.15)\%\ , \end{align*} where the uncertainties are statistical and systematic, respectively. The invariant mass spectra of the \(D\pi\), \(D^*\pi\), and \(D\pi\pi\) systems are studied. Branching fraction products are extracted, among them the first observations of \(B(B^0 \to D_1^-\ell^+\nu_\ell) \times B(D_1^- \to D^-\pi^+\pi^-) = (0.102\pm0.013\pm0.009)\%\) and \(B(B^+ \to \bar{D}_1^0\ell^+\nu_\ell) \times B(\bar{D}_1^0 \to \bar{D}^0\pi^+\pi^-) = (0.105\pm0.011\pm0.008)\%\).
We present measurements of the branching fractions for the singly Cabibbo-suppressed decays \(D^+\to K^{+}K^{-}\pi^{+}\pi^{0}\) and \(D_s^{+}\to K^{+}\pi^{-}\pi^{+}\pi^{0}\), and the doubly ...Cabibbo-suppressed decay \(D^{+}\to K^{+}\pi^{-}\pi^{+}\pi^{0}\), based on 980 \({\rm fb}^{-1}\) of data recorded by the Belle experiment at the KEKB \(e^{+}e^{-}\) collider. We measure these modes relative to the Cabibbo-favored modes \(D^{+}\to K^{-}\pi^{+}\pi^{+}\pi^{0}\) and \(D_s^{+}\to K^{+}K^{-}\pi^{+}\pi^{0}\). Our results for the ratios of branching fractions are \(B(D^{+}\to K^{+}K^{-}\pi^{+}\pi^{0})/B(D^{+}\to K^{-}\pi^{+}\pi^{+}\pi^{0}) = (11.32 \pm 0.13 \pm 0.26)\%\), \(B(D^{+}\to K^{+}\pi^{-}\pi^{+}\pi^{0})/B(D^{+}\to K^{-}\pi^{+}\pi^{+}\pi^{0}) = (1.68 \pm 0.11\pm 0.03)\%\), and \(B(D_s^{+}\to K^{+}\pi^{-}\pi^{+}\pi^{0})/B(D_s^{+}\to K^{+}K^{-}\pi^{+}\pi^{0}) = (17.13 \pm 0.62 \pm 0.51)\%\), where the uncertainties are statistical and systematic, respectively. The second value corresponds to \((5.83\pm 0.42)\times\tan^4\theta_C\), where \(\theta_C\) is the Cabibbo angle; this value is larger than other measured ratios of branching fractions for a doubly Cabibbo-suppressed charm decay to a Cabibbo-favored decay. Multiplying these results by world average values for \(B(D^{+}\to K^{-}\pi^{+}\pi^{+}\pi^{0})\) and \(B(D_s^{+}\to K^{+}K^{-}\pi^{+}\pi^{0})\) yields \(B(D^{+}\to K^{+}K^{-}\pi^{+}\pi^{0})= (7.08\pm 0.08\pm 0.16\pm 0.20)\times10^{-3}\), \(B(D^{+}\to K^{+}\pi^{-}\pi^{+}\pi^{0})= (1.05\pm 0.07\pm 0.02\pm 0.03)\times10^{-3}\), and \(B(D_s^{+}\to K^{+}\pi^{-}\pi^{+}\pi^{0}) = (9.44\pm 0.34\pm 0.28\pm 0.32)\times10^{-3}\), where the third uncertainty is due to the branching fraction of the normalization mode. The first two results are consistent with, but more precise than, the current world averages. The last result is the first measurement of this branching fraction.
We present the study of \(\bar{B}^{0} \to \Sigma_{c}(2455)^{0,++} \pi^{\pm} \bar{p}\) decays based on \(772\times 10^{6}\) \(B\bar{B}\) events collected with the Belle detector at the KEKB ...asymmetric-energy \(e^+e^-\) collider. The \(\Sigma_{c}(2455)^{0,++} \) candidates are reconstructed via their decay to \(\Lambda_{c}^{+} \pi^{\mp}\) and \(\Lambda_{c}^{+}\) decays to \(pK^{-}\pi^{+},~pK_{S}^{0},\) and \(\Lambda\pi^{+}\) final states. The corresponding branching fractions are measured to be \({\cal B}(\bar{B}^{0} \to \Sigma_{c}(2455)^{0} \pi^{+} \bar{p}) = (1.09 \pm 0.06 \pm 0.07)\times10^{-4}\) and \({\cal B}(\bar{B}^{0} \to \Sigma_{c}(2455)^{++} \pi^{-} \bar{p}) = (1.84\pm 0.11 \pm 0.12)\times 10^{-4}\), which are consistent with the world average values with improved precision. A new structure is found in the \(M_{\Sigma_{c}(2455)^{0,++}\pi^{\pm}}\) spectrum with a significance of \(4.2\sigma\) including systematic uncertainty. The structure is possibly an excited \(\Lambda_{c}^{+}\) and is tentatively named \(\Lambda_{c}(2910)^{+}\). Its mass and width are measured to be \((2913.8 \pm 5.6 \pm 3.8)\) MeV/\(c^{2}\) and \((51.8\pm20.0 \pm 18.8)\) MeV, respectively. The products of branching fractions for the \(\Lambda_{c}(2910)^{+}\) are measured to be \({\cal B}(\bar{B}^{0} \to \Lambda_{c}(2910)^{+}\bar{p})\times{\cal B}(\Lambda_{c}(2910)^{+} \to \Sigma_{c}(2455)^{0}\pi^{+}) = (9.5 \pm 3.6 \pm 1.6)\times 10^{-6}\) and \({\cal B}(\bar{B}^{0} \to \Lambda_{c} (2910)^{+}\bar{p})\times {\cal B}(\Lambda_{c}(2910)^{+} \to \Sigma_{c}(2455)^{++}\pi^{-}) = (1.24 \pm 0.35 \pm 0.10)\times 10^{-5}\). Here, the first and second uncertainties are statistical and systematic, respectively.
We search for the tree-diagram dominated process \(B^+ \rightarrow p \overline{n} \pi^0\), using a data sample of \(772 \times 10^6~B\overline B\) pairs collected at the \(\Upsilon(4S)\) resonance ...with the Belle detector at the KEKB asymmetric-energy \(e^+ e^-\) collider. This is the first search with the Belle detector for a decay mode including an anti-neutron. No significant signal is observed and an \(90\%\) credible upper limit on the branching fraction is set at \(6.1\times10^{-6}\).
Using \((771.6 \pm 10.6) \times 10^6\) \(B\bar{B}\) meson pairs recorded by the Belle experiment at the KEKB \(e^+ e^-\) collider, we report the branching fractions \(\mathcal{B}(\bar{B}^0 \to D^{*+} ...\pi^-) = (2.62 \pm 0.02 \pm 0.09)\times 10^{-3}\) and \(\mathcal{B}(\bar{B}^0 \to D^{*+} K^-) = (2.22 \pm 0.06 \pm 0.08)\times 10^{-4}\); the quoted uncertainties are statistical and systematic, respectively. A measurement of the ratio of these branching fractions is also presented, \(\mathcal{R}_{K/\pi}=\mathcal{B}(\bar{B} \to D^{*+}K^-) /\mathcal{B}( \bar{B} \to D^{*+}\pi^-) = (8.41 \pm 0.24 \pm 0.13)\times 10^{-2}\), where systematic uncertainties due to the \(D^{*+}\) meson reconstruction cancel out. Furthermore, we report a new QCD factorization test based on the measured ratios for \(\bar{B} \to D^{*+}h^-\) and \(\bar{B} \to D^{*+}\ell^-\nu\) decays at squared momentum transfer values equivalent to the mass of the \(h = \pi\) or \(K\) hadron. The parameters \(|a_1(h)|\) are measured to be \(|a_1(\pi)|= 0.884 \pm 0.004 \pm 0.003 \pm 0.016\) and \(|a_1(K)|=0.913 \pm 0.019 \pm 0.008 \pm 0.013\), where the last uncertainties account for all external inputs. These values are approximately \(15\%\) lower than those expected from theoretical predictions. Subsequently, flavor \(SU(3)\) symmetry is tested by measuring the ratios for pions and kaons, \(|a_1(K)|^2/ |a_1(\pi)|^2=1.066 \pm 0.042 \pm 0.018 \pm 0.023\), as well as for different particle species. The ratio is consistent with unity and therefore no evidence for \(SU(3)\) symmetry breaking effects is found at the \(5\%\) precision level.
