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B. S. Zou

Publications and source records attributed to B. S. Zou.

At least 91 records · Page 5Linked to original sources
arXiv2003

A study of pentaquark $Θ$ state in the chiral SU(3) quark model

The structure of the pentaquark state uudd-sbar is studied in the chiral SU(3) quark model as well as in the extended chiral SU(3) quark model, in which the vector meson exchanges are included. Four configurations of JP=1/2- and four of JP=1/2+ are considered. The results show that the isospin T=0 state is always the lowest one for both JP=1/2- and JP=1/2+ cases in various models. But the theoretical value of the lowest one is still about 200-300 MeV higher than the experimental mass of $Θ$. It seems that a dynamical calculation should be done for the further study.

hep-ph↗
arXiv2003

One-pion-exchange final-state-interaction and the pbar p near threshold enhancement in J/psi -> gamma pbar p decays

For the Nbar N system, the one-pion-exchange (OPE) interaction gives the largest attractive force for Nbar N with isospin I=0 and spin S=0, while a near threshold enhancement was observed for pbar p with I=0 and S=0 in J/psi -> gamma pbar p decays. With a K-matrix approach, we find that the OPE final-state-interaction (FSI) makes an important contribution to the near-threshold enhancement in the pbar p mass spectrum in J/psi -> gamma pbar p decays.

hep-ph↗
arXiv2003

Diquark model for $J/ ψ$ baryonic decays

The baryonic decays of $J/ ψ$ provide a new way to study the internal structure of baryons. We apply a simple diquark model to the calculation of the decay cross-sections for the reactions $J/ ψ\longrightarrow \bar{p}p$, $\bar pN^*(1440)$, $\bar{N}^{\ast}N^{\ast}$, $\barΛΛ$ and $\barΣ^0Σ^0$. The results are different from those given by the ordinary constituent quark model. Hence these reactions may provide a new check of two different pictures for the baryons.

hep-ph↗
arXiv2003

New study of the isotensor pi-pi interaction

With t-channel rho, f2(1270) exchange and the pi pi -> rho rho -> pi pi box diagram contribution, we reproduce the pi pi isotensor S-wave and D-wave scattering phase shifts and inelasticities up to 2.2 GeV quite well in a K-matrix formalism. The t-channel rho exchange provides repulsive negative phase shifts while the t-channel f2(1270) gives an attractive force to increase the phase shifts for pi pi scattering above 1 GeV, and the coupled-channel box diagram causes the inelasticities. The implication to the isoscalar pi pi S-wave interaction is discussed.

hep-ph↗
arXiv2002

Covariant tensor formalism for partial wave analyses of psi decay to mesons

J/psi and psi' decay to mesons are a good place to look for glueballs, hybrids and for extracting strange and nonstrange components in mesons. Abundant J/psi and psi' events have been collected at the Beijing Electron Positron Collider (BEPC). More data will be collected at upgraded BEPC and CLEO-C. Here we provide explicit PWA formulae for many interesting channels in the covariant tensor formalism.

hep-ph↗
arXiv2002

Covariant L-S Scheme for the effective N*NM couplings

For excited nucleon states $N^*$ of arbitrary spin coupling to nucleon (N) and meson (M), we propose a Lorentz covariant orbital-spin (L-S) scheme for the effective $N^*NM$ couplings. To be used for the partial wave analysis of various $N^*$ production and decay processes, it combines merits of two conventional schemes, {\sl i.e.}, covariant effective Lagrangian approach and multipole analysis with amplitudes expanded according to angular momentum L. As examples, explicit formulae are given for $N^*\to Nπ$, $N^*\to Nω$ and $ψ\to N^*\bar N$ processes which are under current experimental studies.

hep-ph↗
arXiv2002

N* and Meson Resonances in J/psi decays

Over sixty million J/psi events have been collected by the BES Collaboration at the Beijing Electron-Positron Collider (BEPC). J/psi decays provide an excellent place for studying excited nucleons and hyperons -- N*, $Λ^*$, $Σ^*$ and $Ξ^*$ resonances, as well as meson resonances, including possible glueballs and hybrids. Physics objectives, recent results and future prospects of light hadron spectroscopy at BEPC are presented.

hep-ex↗
arXiv2001

Baryon Spectroscopy at Beijing Electron Positron Collider

BES Collaboration has collected 58 million $J/ψ$ events at the Beijing Electron-Positron Collider (BEPC). $J/ψ$ decays provide an excellent place for studying excited nucleons and hyperons -- $N^*$, $Λ^*$, $Σ^*$ and $Ξ^*$ resonances. Physics motivation, data status, partial wave analyses and future prospects are presented for the baryon resonance program at BES.

hep-ph↗
arXiv2001

Study of N*(1440) from J/Psi Decays

For $J/Ψ\to\bar pp π^0$ and $\bar ppπ^+π^-$, the $π^0p$ and $pπ^+π^-$ systems are limited to be pure isospin 1/2 due to isospin conservation. This is a big advantage in studying $N^*$ resonances from $J/Ψ$ decays, compared with $πN$ and $γN$ experiments. The process $J/Ψ\to\bar pN^*$ or $p\bar N^*$ provides a new way to probe the internal structure of the $N^*$ resonances. Here we report a quark model calculation for $J/Ψ\to\bar pp$, $pN^*(1440)$ and $\bar N^*N^*$. The implication for the internal structure of $N^*(1440)$ is discussed.

hep-ph↗
arXiv2000

Light Hadron Spectroscopy at BEPC

The $J/Ψ$ and $Ψ'$ experiments at the Beijing Electron Positron Collider (BEPC) play a unique role in many aspects of light hadron spectroscopy, such as hunting for glueballs and hybrids, extracting $u\bar u+d\bar d$ and $s\bar s$ components of mesons, and studying excited nucleons and hyperons, i.e., $N^*$, $Λ^*$, $Σ^*$ and $Ξ^*$ resonances. Physics objectives, recent results and future prospects of light hadron spectroscopy at BEPC are presented.

hep-ph↗
arXiv2000

The glueball spectrum

Mass ratios of glueballs predicted by the latest Lattice QCD calculations in the quenched approximation agree well with four prime experimental candidates.

hep-ph↗
arXiv2000

N*, Lambda*, Sigma* and Xi* Resonances from J/Psi and Psi' Decays

Vector charmonium states $J/Ψ$ and $Ψ'$ are copiously produced by $e^+e^-$ annihilations at the Beijing Electron Positron Collider (BEPC). Their decays provide an excellent place for studying excited nucleons and hyperons -- $N^*$, $Λ^*$, $Σ^*$ and $Ξ^*$ resonances. The systematic study of these excited nucleons and hyperons can provide us with critical insights into the internal quark structure of baryons.

hep-ph↗
arXiv2000

N* Resonances in e+e- Collisions at Bepc

$J/Ψ$ particles are abundantly produced at the Beijing Electron Positron Collider (BEPC). The $J/Ψ$ decays provide an excellent place for studying $N^*$ resonances. For $J/Ψ\to\bar NNπ$ and $\bar NNππ$, the $πN$ and $ππN$ systems are limited to be pure isospin 1/2 due to isospin conservation. This is a big advantage in studying $N^*$ resonances from $J/Ψ$ decays, compared with $πN$ and $γN$ experiments which suffer difficulty on the isospin decomposition of 1/2 and 3/2. All other $N^*$ decay channels which are presently under investigation at CEBAF(JLab, USA), ELSA(Bonn,Germany) and GRAAL(Grenoble, France) with real photon or space-like virtual photon can also be studied at BEPC complementally with the time-like virtual photon. The process $J/Ψ\to\bar NN^*$ or $N\bar N^*$ provides a new way to probe the internal structure of the $N^*$ resonances. The recent results and outlook of our new $N^*$ program at BEPC are presented.

hep-ph↗
arXiv1999

Charge and critical density of strange quark matter

The electric charge of strange quark matter is of vital importance to experiments. A recent investigation shows that strangelets are most likely highly negatively charged, rather than slightly positively charged as previously believed. Our present study indicates that negative charges can indeed lower the critical density, and thus be favorable to the experimental searches in heavy ion collisions. However, too much negative charges can make it impossible to maintain flavor equilibrium.

hep-ph↗
arXiv1997

Inelastic Rescattering and CP Asymmetries in D -> pi+ pi-, pi0 pi0

We study the direct CP violation induced by inelastic final state interaction (FSI) rescattering in $D\toππ$ modes, and find that the resultant CP asymmetry is about $10^{-4}$ which is larger than $ε'$ in the K-system. Our estimation is based on well-established theories and experiment measured data, so there are almost no free parameters except the weak phase $δ_{13}$ in the CKM matrix.

hep-ph↗
arXiv1996

pi-pi S-Wave Interaction and 0++ Particles

From a re-analysis of pi+ pi- -> pi+ pi- and pi+ pi- -> K K data, we found for pi-pi S-wave interaction below 2 GeV, sigma(400), f0(980), f0(1500) and f0(1780) clearly show up. f0(1370) can be included with a very small branching ratio to pi-pi. f0(1300) and f0(1590) are not real resonances and are due to interference effects of above resonances. The sigma(400) with a width about 700 MeV is mainly produced by t-channel exchange force.

hep-ph↗
arXiv1996

Okubo-Zweig-Iizuka Rule Violation and Possible Explanations

Violations of the Okubo-Zweig-Iizuka (OZI) rule in $s\bar s <-> n\bar n = 1/2 (u\bar u + d\bar d)$ mixing and $ϕ$ production from nucleon-antinucleon annihilation are reviewed. Possible explanations are examined. We conclude that the two-step hadronic loops can explain these OZI violations naturally with proper consideration of cancellations between loops. No conclusive evidence exists for glueball states, $s\bar sn\bar n$ four quark states, instanton effects, and strange quarks in nucleon.

hep-ph↗