Narrow Results

A form to describe hadron strong decays is in terms of quark and gluon degrees of freedom in microscopic decay models. Initially we assume that strong decays are driven by the same inter-quark Hamiltonian which determines the spectrum, and that it incorporates gaussian confinement. An $A\to BC$ decay matrix element of the JKJ Hamiltonian involves a pair-production current matrix elements times a scattering matrix element. Diagrammatically this corresponds to an interaction between an initial line and produced pair. In this work we apply the model to the light meson sector and calculate the decay rate, comparing with the experimental values.

We study hadronic weak decays using an approach which consists in a mapping technique, the Fock-Tani formalism, in order to obtain an effective weak Hamiltonian starting from a contact microscopic interaction. An additional effect is manifest in this formalism associated to the extended nature of mesons: bound-state corrections which can be related to CP violation parameters.

The BESIII Experiment at the Beijing Electron Positron Collider (BEPCII) has accumulated the largest $e^{+}{e}^{-}$ collisions data sets in the $\tau$-charm region in the world. Using the data sets of 448.1 million $\psi (3686)$ events and 1.3 billion $J/\psi$ events, the branching fractions and the angular distributions of $J/\psi$ and $\psi (3686)$ decay to $\mathrm{\Lambda }\bar{\mathrm{\Lambda }}$, ${\mathrm{\Sigma }}^0{\bar{\mathrm{\Sigma }}}^0$, $\mathrm{\Sigma }{(1385)}^0\bar{\mathrm{\Sigma }}{(1385)}^0$ and ${\mathrm{\Xi }}^0{\bar{\mathrm{\Xi }}}^0$ are measured. The branching fractions of $\psi (3686)\to \gamma {\chi }_{cJ}$ are reported with improved precision. The higher-order multipole amplitudes in $\psi (3686)\to \gamma {\chi }_{c1,2}$ with ${\chi }_{c1,2}\to \gamma J/\psi$ are measured, as a byproduct the ${\eta }_c(2S)\to \gamma J/\psi$ transition is searched. The Dalitz decays of $\psi (3686)\to e^{+}{e}^{-}{\chi }_{cJ}$ and ${\chi }_{cJ}\to e^{+}{e}^{-}J/\psi$ are observed and the branching fractions are measured. $h_c$ radiative decays $h_c\to \gamma {\eta }^{\prime }(\eta )$ are observed for the first time. Improved measurement of ${\eta }_c\to \varphi \varphi$ and search for ${\eta }_c\to \omega \varphi$ are reported.