Measurement of e+e−→γχcJe^+e^- \to \gamma\chi_{cJ} via initial state radiation at Belle

The process $e^+e^- \to \gamma\chi_{cJ}$ ($J$=1, 2) is studied via initial state radiation using 980 fb$^{-1}$ of data at and around the $\Upsilon(nS)$ ($n$=1, 2, 3, 4, 5) resonances collected with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. No significant signal is observed except from $\psi(2S)$ decays. Upper limits on the cross sections between $\sqrt{s}=3.80$ and $5.56~{\rm GeV}$ are determined at the 90% credibility level, which range from few pb to a few tens of pb. We also set upper limits on the decay rate of the vector charmonium [$\psi(4040$), $\psi(4160)$, and $\psi(4415)$] and charmoniumlike [$Y(4260)$, $Y(4360)$, and $Y(4660)$] states to $\gamma\chi_{cJ}$.Comment: Accepted by PR

Study of π0\pi^0 pair production in single-tag two-photon collisions

We report a measurement of the differential cross section of $\pi^0$ pair production in single-tag two-photon collisions, $\gamma^* \gamma \to \pi^0 \pi^0$, in $e^+ e^-$ scattering. The cross section is measured for $Q^2$ up to 30 GeV$^2$, where $Q^2$ is the negative of the invariant mass squared of the tagged photon, in the kinematic range 0.5 GeV < W < 2.1 GeV and $|\cos \theta^*|$ < 1.0 for the total energy and pion scattering angle, respectively, in the $\gamma^* \gamma$ center-of-mass system. The results are based on a data sample of 759 fb$^{-1}$ collected with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. The transition form factor of the $f_0(980)$ and that of the $f_2(1270)$ with the helicity-0, -1, and -2 components separately are measured for the first time and are compared with theoretical calculations.Comment: 36 pages, 37 figures, 11 tables, Belle Preprint 2015-15, KEK Preprint 2015-2

Evidence of Υ(1S)→J/ψ+χc1\Upsilon(1S) \to J/\psi+\chi_{c1} and search for double-charmonium production in Υ(1S)\Upsilon(1S) and Υ(2S)\Upsilon(2S) decays

Using data samples of $102\times10^6$ $\Upsilon(1S)$ and $158\times10^6$ $\Upsilon(2S)$ events collected with the Belle detector, a first experimental search has been made for double-charmonium production in the exclusive decays $\Upsilon(1S,2S)\rightarrow J/\psi(\psi')+X$, where $X=\eta_c$, $\chi_{cJ} (J=~0,~1,~2)$, $\eta_c(2S)$, $X(3940)$, and $X(4160)$. No significant signal is observed in the spectra of the mass recoiling against the reconstructed $J/\psi$ or $\psi'$ except for the evidence of $\chi_{c1}$ production with a significance of $4.6\sigma$ for $\Upsilon(1S)\rightarrow J/\psi+\chi_{c1}$. The measured branching fraction \BR(\Upsilon(1S)\rightarrow J/\psi+\chi_{c1}) is $(3.90\pm1.21(\rm stat.)\pm0.23 (\rm syst.))\times10^{-6}$. The $90\%$ confidence level upper limits on the branching fractions of the other modes having a significance of less than $3\sigma$ are determined. These results are consistent with theoretical calculations using the nonrelativistic QCD factorization approach.Comment: 12 pages, 4 figures, 1 table. The fit range was extended to include X(4160) signal according to referee's suggestions. Other results unchanged. Paper was accepted for publication as a regular article in Physical Review

Measurements of the Υ(10860)\Upsilon(10860) and Υ(11020)\Upsilon(11020) resonances via σ(e+e−→Υ(nS)π+π−)\sigma(e^+e^-\rightarrow\Upsilon(n{\rm S})\pi^+\pi^-)

We report new measurements of the total cross sections for $e^+e^-\to \Upsilon(n{\rm S})\pi^+\pi^-$ ($n$ = 1, 2, 3) and $e^+e^-\to b\bar b$ from a high-luminosity fine scan of the region $\sqrt{s} = 10.63$-$11.05$ GeV with the Belle detector. We observe that the $\Upsilon(n{\rm S})\pi^+\pi^-$ spectra have little or no non-resonant component and extract from them the masses and widths of $\Upsilon(10860)$ and $\Upsilon(11020)$ and their relative phase. We find $M_{10860}=(10891.1\pm3.2^{+0.6}_{-1.7})$ MeV/$c^2$ and \Gamma_{10860}=(53.7^{+7.1}_{-5.6}\,^{+1.3}_{-5.4}) MeV and report first measurements M_{11020}=(10987.5^{+6.4}_{-2.5}\,^{+9.0}_{-2.1}) MeV/$c^2$, \Gamma_{11020}=(61^{+9}_{-19}\,^{+2}_{-20}) MeV, and \phi_{\rm 11020}-\phi_{\rm 10860} = (-1.0\pm0.4\,^{+1.4}_{-0.1}) rad.Comment: University of Cincinnati preprint UCHEP-15-01, submitted to Physical Review D - Rapid Communication

Observation of B0→pΛˉD(∗)−B^{0} \rightarrow p\bar{\Lambda} D^{(*)-}

We report the first observation of the decays $B^0 \rightarrow p\bar{\Lambda} D^{(*)-}$. The data sample of $711$ fb$^{-1}$ used in this analysis corresponds to $772$ million $B\bar{B}$ pairs, collected at the $\Upsilon(4S)$ resonance by the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. We observe $19.8\sigma$ and $10.8\sigma$ excesses of events for the two decay modes and measure the branching fractions of $B^0 \rightarrow p\bar{\Lambda} D^{-}$ and $B^0 \rightarrow p\bar{\Lambda} D^{*-}$ to be $(25.1\pm2.6\pm3.5)\times10^{-6}$ and $(33.6\pm6.3\pm4.4)\times10^{-6}$, respectively, where the first uncertainties are statistical and the second are systematic. These results are not compatible with the predictions based on the generalized factorization approach. In addition, a threshold enhancement in the di-baryon ($p\bar{\Lambda}$) system is observed, consistent with that observed in similar $B$ decays.Comment: 16 pages, 3 figures and 3 tables, submitted to PR

Observation of a new charged charmoniumlike state in B -> J/psi K pi decays

We present the results of an amplitude analysis of anti-B0 -> J/psi K- pi+ decays. A new charged charmoniumlike state Zc(4200)+ decaying to J/psi pi+ is observed with a significance of 6.2 sigma. The mass and width of the Zc(4200)+ are 4196 +31-29 +17-13 MeV/c^2 and 370 +70-70 +70-132 MeV, respectively; the preferred assignment of the quantum numbers is J^P = 1^+. In addition, we find evidence for Zc(4430)+ -> J/psi pi+. The analysis is based on a 711 fb^-1 data sample collected by the Belle detector at the asymmetric-energy e+ e- collider KEKB.Comment: 14 pages, 13 figure

Measurement of the branching ratio of Bˉ→D(∗)τ−νˉτ\bar{B} \to D^{(\ast)} \tau^- \bar{\nu}_\tau relative to Bˉ→D(∗)ℓ−νˉℓ\bar{B} \to D^{(\ast)} \ell^- \bar{\nu}_\ell decays with hadronic tagging at Belle

We report a measurement of the branching fraction ratios R(D(*)) of Bbar -> D(*) tau- nubar_tau relative to Bbar -> D()* l- nubar_l (where l = e or mu) using the full Belle data sample of 772 x 10^6 BBbar pairs collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. The measured values are R(D)= 0.375 +- 0.064(stat.) +- 0.026(syst.) and R(D*) = 0.293 +- 0.038(stat.) +- 0.015(syst.). The analysis uses hadronic reconstruction of the tag-side B meson and purely leptonic tau decays. The results are consistent with earlier measurements and do not show a significant deviation from the standard model prediction.Comment: Accepted for publication in Phys.Rev.

Measurement of the τ\tau lepton polarization and R(D∗)R(D^*) in the decay Bˉ→D∗τ−νˉτ\bar{B} \to D^* \tau^- \bar{\nu}_\tau

We report the first measurement of the $\tau$ lepton polarization $P_\tau(D^*)$ in the decay $\bar{B} \rightarrow D^* \tau^- \bar{\nu}_\tau$ as well as a new measurement of the ratio of the branching fractions $R(D^{*}) = \mathcal{B}(\bar {B} \rightarrow D^* \tau^- \bar{\nu}_\tau) / \mathcal{B}(\bar{B} \rightarrow D^* \ell^- \bar{\nu}_\ell)$, where $\ell^-$ denotes an electron or a muon, and the $\tau$ is reconstructed in the modes $\tau^- \rightarrow \pi^- \nu_\tau$ and $\tau^- \rightarrow \rho^- \nu_\tau$. We use the full data sample of $772 \times 10^6$ $B{\bar B}$ pairs recorded with the Belle detector at the KEKB electron-positron collider. Our results, $P_\tau(D^*) = -0.38 \pm 0.51 {\rm (stat.)} ^{+0.21}_{-0.16} {\rm (syst.)}$ and $R(D^*) = 0.270 \pm 0.035{\rm (stat.)} ^{+0.028}_{-0.025}{\rm (syst.)}$, are consistent with the theoretical predictions of the Standard Model.Comment: 7 pages, 2 figures, submitted to Physical Review Letters; one figure was removed from the first versio