Dihydroxylation of double-stranded poly(bisnorbornene) (6) with a ferrocene linker gives the corresponding poly(bisnorbornanediol) (15) diasteroselectively. The structures of polymers were ...characterized by spectroscopic means and STM images. Hydrolysis of 6 gives the corresponding isotactic single-stranded polynorbornene (12) having similar polydispersity and degree of polymerization as those of 6. The STM image of the hydrogenated double-stranded polymer 13 clearly shows the double-stranded structure, and the spacing between two neighboring ferrocene linkers is 0.6 nm. In addition, poly(bisnorbornanediol) (15) forms ordered aggregation assembled via hydrogen bonding in both longitudinal and horizontal dimensions.
We report measurements of time-dependent \(CP\) asymmetries in \(B^0 \to K^0_S \pi^0 \gamma\) decays based on a data sample of \((388\pm6)\times10^6\) \(B\bar{B}\) events collected at the ...\(\Upsilon(4S)\) resonance with the Belle II detector. The Belle II experiment operates at the SuperKEKB asymmetric-energy \(e^+e^-\) collider. We measure decay-time distributions to determine \(CP\)-violating parameters \(S\) and \(C\). We determine these parameters for two ranges of \(K^0_S \pi^0\) invariant mass: \(m(K^0_S \pi^0)\in (0.8, 1.0)\) \(GeV/c^2\), which is dominated by \(B^0 \to K^{*0} (\to K^0_S \pi^0) \gamma\) decays, and a complementary region \(m(K^0_S \pi^0)\in (0.6, 0.8)\cup(1.0, 1.8)\) \(GeV/c^2\). Our results have improved precision as compared to previous measurements and are consistent with theory predictions.
We present measurements of \(B^{+}\rightarrow\rho^{+}\gamma\) and \(B^{0}\rightarrow\rho^{0}\gamma\) decays using a combined data sample of \(772 \times 10^6\) \(B\overline{B}\) pairs collected by ...the Belle experiment and \(387\times 10^6\) \(B\overline{B}\) pairs collected by the Belle II experiment in \(e^{+}e^{-}\) collisions at the \(\Upsilon (4S)\) resonance. After an optimized selection, a simultaneous fit to the Belle and Belle II data sets yields \(114\pm 12\) \(B^{+}\rightarrow\rho^{+}\gamma\) and \(99\pm 12\) \(B^{0}\rightarrow\rho^{0}\gamma\) decays. The measured branching fractions are \((13.1^{+2.0 +1.3}_{-1.9 -1.2})\times 10^{-7}\) and \((7.5\pm 1.3^{+1.0}_{-0.8})\times 10^{-7}\) for \(B^{+}\rightarrow\rho^{+}\gamma\) and \(B^{0}\rightarrow\rho^{0}\gamma\) decays, respectively, where the first uncertainty is statistical and the second is systematic. We also measure the isospin asymmetry \(A_{\rm I}(B\rightarrow\rho\gamma)=(10.9^{+11.2 +7.8}_{-11.7 -7.3})\%\) and the direct CP asymmetry \(A_{CP}(B^{+}\rightarrow\rho^{+}\gamma)=(-8.2\pm 15.2^{+1.6}_{-1.2})\%\).
We present a search for the baryon number \(B\) and lepton number \(L\) violating decays \(\tau^- \rightarrow \Lambda \pi^-\) and \(\tau^- \rightarrow \bar{\Lambda} \pi^-\) produced from the ...\(e^+e^-\to \tau^+\tau^-\) process, using a 364 fb\(^{-1}\) data sample collected by the Belle~II experiment at the SuperKEKB collider. No evidence of signal is found in either decay mode, which have \(|\Delta(B-L)|\) equal to \(2\) and \(0\), respectively. Upper limits at 90\% credibility level on the branching fractions of \(\tau^- \rightarrow \Lambda\pi^-\) and \(\tau^- \rightarrow \bar{\Lambda}\pi^-\) are determined to be \(4.7 \times 10^{-8}\) and \(4.3 \times 10^{-8}\), respectively.
We measure the branching fraction of the decay \(B^- \to D^0 \rho(770)^-\) using data collected with the Belle II detector. The data contain 387 million \(B\overline{B}\) pairs produced in \(e^+e^-\) ...collisions at the \(\Upsilon(4S)\) resonance. We reconstruct \(8360\pm 180\) decays from an analysis of the distributions of the \(B^-\) energy and the \(\rho(770)^-\) helicity angle. We determine the branching fraction to be \((0.939 \pm 0.021\mathrm{(stat)} \pm 0.050\mathrm{(syst)})\%\), in agreement with previous results. Our measurement improves the relative precision of the world average by more than a factor of two.
We report on a search for a resonance \(X\) decaying to a pair of muons in \(e^{+}e^{-}\rightarrow \mu^+ \mu^- X\) events in the 0.212-9.000 GeV/\(c^{2}\) mass range, using 178 fb\(^{-1}\) of data ...collected by the BelleII experiment at the SuperKEKB collider at a center of mass energy of 10.58 GeV. The analysis probes two different models of \(X\) beyond the standard model: a \(Z^{\prime}\) vector boson in the \(L_{\mu}-L_{\tau}\) model and a muonphilic scalar. We observe no evidence for a signal and set exclusion limits at the 90\(\%\) confidence level on the products of cross section and branching fraction for these processes, ranging from 0.046 fb to 0.97 fb for the \(L_{\mu}-L_{\tau}\) model and from 0.055 fb to 1.3 fb for the muonphilic scalar model. For masses below 6 GeV/\(c^{2}\), the corresponding constraints on the couplings of these processes to the standard model range from 0.0008 to 0.039 for the \(L_{\mu}-L_{\tau}\) model and from 0.0018 to 0.040 for the muonphilic scalar model. These are the first constraints on the muonphilic scalar from a dedicated search.
We present an analysis of the process \(e^{+}e^{-}\to\pi^{+}\pi^{-}\Upsilon(nS)\) (where \(n\) = 1, 2, or 3) reconstructed in \(19.6\rm\) \(\rm fb^{-1}\) of Belle II data during a special run of the ...SuperKEKB collider at four energy points near the peak of the \(\Upsilon(10753)\) resonance. By analyzing the mass distribution of the \(\pi^+\pi^-\Upsilon(nS)\) system and the Born cross sections of the \(e^{+}e^{-}\to\pi^{+}\pi^{-}\Upsilon(nS)\) process, we report the first observation of \(\Upsilon(10753)\) decays to the \(\pi^{+}\pi^{-}\Upsilon(1S)\) and \(\pi^{+}\pi^{-}\Upsilon(2S)\) final states, and find no evidence for decays to \(\pi^{+}\pi^{-}\Upsilon(3S)\). Possible intermediate states in the \(\pi^+\pi^-\Upsilon(1S,2S)\) transitions are also investigated, and no evidence for decays proceeding via the \(\pi^\mp Z_b^\pm\) or \(f_0(980)\Upsilon(nS)\) intermediate states is found. We measure Born cross sections for the \(e^{+}e^{-}\to\pi^{+}\pi^{-}\Upsilon(nS)\) process that, combined with results from Belle, improve the precision of measurements of the \(\Upsilon(10753)\) mass and width by nearly a factor of two to \((10756.3\pm2.7\pm0.6)\) MeV/\(c^2\) and \((29.7\pm8.5\pm1.1)\) MeV, respectively. The relative ratios of the Born cross sections at the \(\Upsilon(10753)\) resonance peak are also reported for the first time.
We present a study of \(\Xi_{c}^{0}\to\Xi^{0}\pi^{0}\), \(\Xi_{c}^{0}\to\Xi^{0}\eta\), and \(\Xi_{c}^{0}\to\Xi^{0}\eta^{\prime}\) decays using the Belle and Belle~II data samples, which have ...integrated luminosities of 980~\(\mathrm{fb}^{-1}\) and 426~\(\mathrm{fb}^{-1}\), respectively. We measure the following relative branching fractions $${\cal B}(\Xi_{c}^{0}\to\Xi^{0}\pi^{0})/{\cal B}(\Xi_{c}^{0}\to\Xi^{-}\pi^{+}) = 0.48 \pm 0.02 ({\rm stat}) \pm 0.03 ({\rm syst}) ,$$ $${\cal B}(\Xi_{c}^{0}\to\Xi^{0}\eta)/{\cal B}(\Xi_{c}^{0}\to\Xi^{-}\pi^{+}) = 0.11 \pm 0.01 ({\rm stat}) \pm 0.01 ({\rm syst}) ,$$ $${\cal B}(\Xi_{c}^{0}\to\Xi^{0}\eta^{\prime})/{\cal B}(\Xi_{c}^{0}\to\Xi^{-}\pi^{+}) = 0.08 \pm 0.02 ({\rm stat}) \pm 0.01 ({\rm syst}) $$ for the first time, where the uncertainties are statistical (\(\rm stat\)) and systematic (\(\rm syst\)). By multiplying by the branching fraction of the normalization mode, \({\mathcal B}(\Xi_{c}^{0}\to\Xi^{-}\pi^{+})\), we obtain the following absolute branching fraction results \((6.9 \pm 0.3 ({\rm stat}) \pm 0.5 ({\rm syst}) \pm 1.3 ({\rm norm})) \times 10^{-3}\), \((1.6 \pm 0.2 ({\rm stat}) \pm 0.2 ({\rm syst}) \pm 0.3 ({\rm norm})) \times 10^{-3}\), and \((1.2 \pm 0.3 ({\rm stat}) \pm 0.1 ({\rm syst}) \pm 0.2 ({\rm norm})) \times 10^{-3}\), for \(\Xi_{c}^{0}\) decays to \(\Xi^{0}\pi^{0}\), \(\Xi^{0}\eta\), and \(\Xi^{0}\eta^{\prime}\) final states, respectively. The third errors are from the uncertainty on \({\mathcal B}(\Xi_{c}^{0}\to\Xi^{-}\pi^{+})\). The asymmetry parameter for \(\Xi_{c}^{0}\to\Xi^{0}\pi^{0}\) is measured to be \(\alpha(\Xi_{c}^{0}\to\Xi^{0}\pi^{0}) = -0.90\pm0.15({\rm stat})\pm0.23({\rm syst})\).
We present a measurement of the ratio \(R_\mu = \mathcal{B}(\tau^-\to \mu^-\bar\nu_\mu\nu_\tau) / \mathcal{B}(\tau^-\to e^-\bar\nu_e\nu_\tau)\) of branching fractions \(\mathcal{B}\) of the \(\tau\) ...lepton decaying to muons or electrons using data collected with the Belle II detector at the SuperKEKB \(e^+e^-\) collider. The sample has an integrated luminosity of 362 fb\(^{-1}\) at a centre-of-mass energy of 10.58 GeV. Using an optimised event selection, a binned maximum likelihood fit is performed using the momentum spectra of the electron and muon candidates. The result, \(R_\mu = 0.9675 \pm 0.0007 \pm 0.0036\), where the first uncertainty is statistical and the second is systematic, is the most precise to date. It provides a stringent test of the light-lepton universality, translating to a ratio of the couplings of the muon and electron to the \(W\) boson in \(\tau\) decays of \(0.9974 \pm 0.0019\), in agreement with the standard model expectation of unity.
We present the result of a search for the charged-lepton-flavor violating decay \(\tau^- \to \mu^-\mu^+\mu^-\) using a \(424fb^{-1}\) sample of data recorded by the Belle II experiment at the ...SuperKEKB \(e^{-}e^{+}\) collider. The selection of \(e^{-}e^{+}\to\tau^+\tau^-\) events is based on an inclusive reconstruction of the non-signal tau decay, and on a boosted decision tree to suppress background. We observe one signal candidate, which is compatible with the expectation from background processes. We set a \(90\%\) confidence level upper limit of \(1.9 \times 10^{-8}\) on the branching fraction of the \taumu decay, which is the most stringent bound to date.
