New Heavy Exotic Hadrons

Abstract

We review recent studies on exotic states at the Belle experiment. The results include: (1) The measurement of the cross sections of $\gamma \gamma \to \omega \varphi$, $\varphi \varphi$, and $\omega \omega$ for masses that range from threshold to 4.0 GeV. In addition to signals from well established spin-zero and spin-two charmonium states, there are clear resonant structures below charmonium threshold, which have not been previously observed. We report a spin-parity analysis for the new structures; (2) No X(3872) signal is observed in $\eta J/\psi$ or $\gamma {\chi }_{c1}$ mode in B decays. A narrow peak at 3823.5 MeV/$c^2$ (named as ${\psi }_2$) to $\gamma {\chi }_{c1}$ with a significance of 4.2 standard deviations including systematic uncertainty is observed in $B^{\pm }\to K^{\pm }\gamma {\chi }_{c1}$; (3) The bottomonium states $h_b(1P)$, $h_b(2P)$ and ${\rm Y}(1D)$ are observed in the reaction $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}+X$; (4) The observation of two narrow charged structures (named as $Z_b(10610)$ and $Z_b(10650)$) in the mass spectra of the ${\pi }^{\pm }{\rm Y}(nS)(n=1,2,3)$ and ${\pi }^{\pm }{h}_b(mP)$ $(m=1,2)$ pairs that are produced in association with a single charged pion in Y(5S) decays.

arXiv comment7 pages, 7 figures, Prepared for the Sixth International Conference on Quarks and Nuclear Physics QNP2012, April 16-20, 2012, Ecole Polytechnique, Palaiseau, France