20-27 July 2011
Alpes Congrès - Alpexpo
Europe/Paris timezone

Charmonium and X, Y, Z at Belle

22 Jul 2011, 14:30
les Ecrins 3 (Alpes Congrès - Alpexpo)

les Ecrins 3

Alpes Congrès - Alpexpo

Parallel session talk Flavour Physics and Fundamental Symmetries Flavour Physics and Fundamental Symmetries


Ms Anna Vinokurova (Budker Institute)


We report results of a study of charmonium and X, Y, Z states using the world-largest data sample accumulated with the Belle detector at the KEKB asymmetric-energy e+e- collider. : We present results from a study of $X(3872) \to J/\psi \pi^+ \pi^-$ decays produced in exclusive $B\to K \pi^+ \pi^- J/\psi$ decays using the full Belle data set. We present new measurements of the $X(3872)$ mass and width and the $BF(B \to K X(3872)) \times BF(X(3872) \to \pi^+ \pi^- J/\psi)$ product branching fractions for both charged and neutral $B$ mesons. A new measurement of the difference in mass between $X(3872) \to \pi^+ \pi^- J/\psi$ signals in $B^+$ and $B^0$ decays and results of a search for a charged partner of the $X(3872)$ in the decay $B \to K X^+, X^+ \to \pi^+ \pi^0 J/\psi$ are reported. In addition, we examine possible $J^{PC}$ quantum number assignments for the $X(3872)$ based on comparisons of angular correlations among final state particles in $X(3872) \to \pi^+ \pi^- J/\psi$ decays with simulated data for $J^{PC}$ values of $1^{++}$ and $2^{-+}$. We examine the influence of $\rho-\omega$ interference in the $M(\pi^+\pi^-)$ spectrum. The analysis is based on a 711 fb$^{-1}$ data sample that contains 772 million $B\bar{B}$ meson pairs collected at the $\Upsilon(4S)$ resonance in the Belle detector at the KEKB collider. We report a study of $B\to (J/\psi \gamma) K$ and $B\to (\psi' \gamma)K$ decay modes using $772\times 10^{6}$ $B\overline{B}$ events collected at the $\Upsilon(4S)$ resonance. We observe $X(3872) \to J/\psi \gamma$ and report the first evidence for $\chi_{c2} \to J/\psi \gamma$ in $B\to (X_{c\overline{c}}\gamma) K$ decays, while in a search for $X(3872) \to \psi' \gamma$ no significant signal is found. We measure the cross section for $e^+e^- \to \pi^0 \pi^0 J/\psi$ from threshold up to 6 GeV using initial state radiation events from $e^+e^-$ annihilation at $\sqrt{s}=10.58$ GeV. We reconstruct the $J/\psi$ in its di-muon decay mode. Using this data we search for evidence of $Y(4260)$ decaying to $\pi^0 \pi^0 J/\psi$. This analysis is based on a data sample with an integrated luminosity of 791 fb$^{-1}$ collected with the Belle detector. We present the results of an amplitude analysis of the $\bar{B}^0 \to J/\psi K^- \pi^+$ decays. A search for charged charmonium-like states in the $J/\psi \pi^+$ system has been performed. We have measured the helicity amplitudes of the resonances in the $K^- \pi^+$ system. The analysis is based on 711 fb$^{-1}$ data sample collected by the Belle detector. We report the results of a study of $B^{\pm}\to K^{\pm}\eta_c$ and $B^{\pm}\to K^{\pm}\eta_c(2S)$ decays followed by $\eta_c$ and $\eta_c(2S)$ decays to $(K_S K\pi)^0$. The results are obtained from a data sample containing 535 million $B\bar{B}$-meson pairs collected in the Belle experiment. We measure the products of the branching fractions ${\mathcal B}(B^{\pm}\to K^{\pm}\eta_c){\mathcal B} (\eta_c\to K_S K^{\pm}\pi^{\mp})$ and ${\mathcal B}(B^{\pm}\to K^{\pm}\eta_c(2S)) {\mathcal B}(\eta_c(2S)\to K_S K^{\pm}\pi^{\mp})$. Interference with the non-resonant component leads to significant model uncertainty in the measurement of these product branching fractions. Our analysis accounts for this interference and allows the model uncertainty to be reduced. We also obtain the masses and widths of the above mentioned charmonia. In the $\eta_c(2S)$ case the results are significantly affected by the interference and also include a model uncertainty. The subject of this analysis is the $Y(3940)$ enhancement at about 3940 MeV. The mass and decay width have been determined by the Belle collaboration upon discovery and were later confirmed by BaBar. Additional quantum numbers, however have not been measured yet. The decay channels, used in this analysis are $B^0 \to J/\psi \omega K^0_S$ and $B^+ \to J/\psi \omega K^+$ (and charge conjugate). $J^{PC}$ shall be determined through an angular distribution analysis of Belle data equivalent to 711 fb$^{-1}$, as well as improvements made in mass and decay width measurements. With a better understanding of the resonances quantum numbers, hopefully statements regarding its theoretical interpretation can be made.

Primary author

Ms Anna Vinokurova (Budker Institute)

Presentation Materials