Study of Scalar Mesons at BES-II

Recent results from BES-II experiment on hadron spectroscopy using \jpsi and $\psi^\prime$ data samples collected in $e^+e^-$ annihilation are presented, including study of the scalar particles in \jpsi radiative and hadronic decays, the observation of X(1810) in $J/\psi \to \gamma \phi \omega$, as well as pair productions of scalars in $\chi_{c0}$ hadronic decays.Comment: Talk on "Hadron spectroscopy at BES" at "From Phi to Psi" Workshop February 27 - March 2, 2006, Novosibirsk, Russi

Recent BES Results on Hadron Spectroscopy

We present recent results from the BES experiment on the observation of the Y(2175) in J/\psi\to \phi f_0(980) \eta, study of \eta(2225) in J/\psi\to \gamma \phi \phi, and the production of X(1440) recoiling against an \omega or a \phi in J/\psi hadronic decays. The observation of \psi(2S) radiative decays is also presented.Comment: 5 page

Survival before annihilation in Psi-prime decays

We extend the simple scenario for $\Psi'$ decays suggested a few years ago. The $c\bar c$ pair in the $\Psi'$ does not annihilate directly into three gluons but rather survives before annihilating. An interesting prediction is that a large fraction of all $\Psi'$ decays could originate from the $\Psi' \to \eta_{c} (3\pi)$ channel which we urge experimentalists to identify. Our model solves the problem of the apparent hadronic excess in $\Psi'$ decays as well as the $\rho\pi$ puzzle since, in our view, the two-body decays of the $\Psi'$ are naturally of electromagnetic origin. Further tests of this picture are proposed, e.g. $J/\Psi \to b_{1}\eta$.Comment: 6 pages, no figur

The puzzle of excessive non-DDˉD\bar D component of the inclusive ψ(3770)\psi(3770) decay and the long-distant contribution

In this letter we suggest that the obvious discrepancy between theoretical prediction on the $\mathrm{non}-D\bar D$ decays of $\psi(3770)$ and data is to be alleviated by taking final state interaction (FSI) into account. By assuming that $\psi(3770)$ overwhelmingly dissociates into $D\bar D$, then the final state interaction induces a secondary process, we calculate the branching ratios of $\psi(3770)\to D\bar D\to J/\psi\eta, \rho\pi, \omega\eta, K^*K$. Our results show that the branching ratio of $\psi(3770)\to \mathrm{non}-D\bar{D}$ can reach up to $\mathcal{B}_{\mathrm{non}-D\bar{D}}^{FSI}=(0.2\sim1.1)$ while typical parameters $I=0.4$ GeV$^{-2}$ and $\alpha=0.8\sim 1.3$ are adopted. This indicates that the FSI is obviously non-negligible.Comment: 6 pages, 4 figures, 1 tables. More references and discussions added, typos corrected. Accepted by Phys. Lett.

Multiquark Hadrons

A number of candidate multiquark hadrons, i.e., particle resonances with substructures that are more complex than the quark-antiquark mesons and three-quark baryons that are prescribed in the textbooks, have recently been observed. In this talk I present: some recent preliminary BESIII results on the near-threshold behavior of sigma(e+e- --> Lambda Lambda-bar) that may or may not be related to multiquark mesons in the light- and strange-quark sectors; results from Belle and LHCb on the electrically charged, charmoniumlike Z(4430)^+ --> pi^+ psi ' resonance that necessarily has a four-quark substructure; and the recent LHCb discovery of the P_c(4380) and P_c(4450) hidden-charm resonances seen as a complex structure in the J/psi p invariant mass distribution for Lambda_b --> K^-J/psi p decays and necessarily have a five-quark substructure and are, therefore, prominent candidates for pentaquark baryons.Comment: 12 pages, 9 figures, summary of a talk presented at the 12th Conference on Hypernuclear and Strange Particle Physics (HYP2015), September 7-12, 2015 Sendai, JAPAN. To appear in the JPS Conference proceeding

Light Meson Decays at BESIII

At present the world’s largest sample of 1.3 billion J/ψ events was accumulated at the BESIII detector, which offers a unique place to study light meson decays. The recent results on the light meson decays are reviewed in this talk. An emphasis is put on the significant progresses on the study of η/η′ decays, including Dalitz plot analysis of η/η′ → πππ, observation of new decay modes (η′ → π+π−π+(0)π−(0), η′ → ρ±π∓, η′ → γe+e− and η′ → e+e−ω), study of η′ → γπ+π− and search for the rare decay of η′ → Kπ. In addition, a prospect on the Dalitz plot analysis of ω → π+π−π0 is presented

Probing scalar meson structures in χc1\chi_{c1} decays into pseudoscalar and scalar

We evaluate the decay branching ratios of $\chi_{c1}\to PS$, in a quark model parametrization scheme, where $P$ and $S$ stand for pseudoscalar and scalar meson, respectively. An interesting feature of this decay process is that the $c\bar{c}$ annihilate via the pQCD hair-pin diagram is supposed to be dominant. Hence, this decay process should be sensitive to the quark components of the final-state light mesons, and would provide a great opportunity for testing the mixing relations among the scalar mesons, i.e. $f_0(1370)$, $f_0(1500)$ and $f_0(1710)$, by tagging the final state pseudoscalar mesons.Comment: 9 pages and 6 eps figures; Enhanced discussion on the dominance of hair-pin diagram is added. Revised version to appear in IJMP