arXiv subjects

Bing-Song Zou

Publications and source records attributed to Bing-Song Zou.

At least 109 records · Page 6Linked to original sources

arXiv2013

Understanding the property of $η(1405/1475)$ in the $J/ψ$ radiative decay

In this work we make a systematic analysis of the correlated processes $J/ψ\to γη(1440)/f_1(1420)$ with $η(1440)/f_1(1420)\to K\bar{K}π$, $ηππ$ and $3π$, where the role played by the so-called "triangle singularity mechanism" (TSM) is clarified. Our results agree well with the experimental data and suggest a small fraction of $f_1(1420)$ contributions in these processes. This study confirms our conclusion in [Phys. Rev. Lett. 108, 081803 (2012)] that the dynamic feature of the TSM can be recognized by the strong narrow peak observed in the $ππ$ invariant mass spectrum of $η(1440)\to 3π$ with anomalously large isospin violations. Nevertheless, we explicitly demonstrate that the TSM can produce obvious peak position shifts for the same $η(1440)$ or $f_1(1420)$ state in different decay channels. This is a strong evidence that the $η(1405)$ and $η(1475)$ are actually the same state, i.e. $η(1440)$. We also make an analysis of the radiative decays of $η(1440)\to γV$ ($V=ϕ$, $ρ^0$ or $ω$) which shows that such a one-state prescription seems not to have a conflict with the so-far existing experimental data. Our analysis may shed a light on the long-standing puzzling question on the nature of $η(1405)$ and $η(1475)$.

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arXiv2012

Resonances contribution to two-photon exchange effects and possible large forward-backward asymmetry in $e^+ e^- \rightarrow p \bar{p}$

The resonances ($η_c,χ_{c0,c2}$) contribution to two-photon exchange (TPE) effects in $e^+ e^- \leftrightarrow p \bar{p}$ is calculated in a simple hadronic model. The calculation shows the TPE contributions by resonance $χ_{c2}$, which are dependent on the unknown phases $ϕ_{E,M}$ of proton's time-like form factors $G_{E,M}$, are much larger than the TPE contributions by non-resonance and are comparable with measurement precision of coming PANDA detector at $\sqrt{s} \sim M_{χ_{c2}}$ for most $ϕ_{E,M}$.

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arXiv2012

The puzzle of anomalously large isospin violations in $η(1405/1475)\to 3π$

The BES-III Collaboration recently report the observation of anomalously large isospin violations in $J/ψ\to γη(1405/1475) \to γπ^0 f_0(980)\to γ+3π$, where the $f_0(980)$ in the $ππ$ invariant mass spectrum appears to be much narrower ($\sim$ 10 MeV) than the peak width ($\sim$50 MeV) measured in other processes. We show that a mechanism, named as triangle singularity (TS), can produce a narrow enhancement between the charged and neutral $K\bar{K}$ thresholds, i.e., $2m_{K^\pm}\sim 2m_{K^0}$. It can also lead to different invariant mass spectra for $η(1405/1475)\to a_0(980)π$ and $K\bar{K}^*+c.c.$, which can possibly explain the long-standing puzzle about the need for two close states $η(1405)$ and $η(1475)$ in $ηππ$ and $K\bar{K}π$, respectively. The TS could be a key to our understanding of the nature of $η(1405/1475)$ and advance our knowledge about the mixing between $a_0(980)$ and $f_0(980)$.

hep-ph↗

arXiv2011

Penta-quark states with hidden charm and beauty

More and more hadron states are found to be difficult to be accommodated by the quenched quark models which describe baryons as 3-quark states and mesons as antiquark-quark states. Dragging out an antiquark-quark pair from the gluon field in hadrons should be an important excitation mechanism for hadron spectroscopy. Our recent progress on the penta-quark states with hidden charm and beauty is reviewed.

hep-ph↗

arXiv2011

Phenomenological study on the $\bar p N\to \bar NNππ$ reactions

We extend our recent phenomenological study of $pN \to NNππ$ reactions to the $\bar{p}N \to \bar{N}Nππ$ reactions for anti-proton beam momenta up to 3.0 GeV within an effective Lagrangian approach. The contribution of $N^*(1440)$ with its $Nσ$ decay mode is found to be dominant at the energies close to threshold for $\bar NNπ^+π^-$ and $\bar NNπ^0π^0$ channels. At higher energies or for $p\bar nπ^-π^-$ and $\bar NNπ^\pmπ^0$ channels where $N^*(1440)\to Nσ$ mode cannot contribute, large contributions from double-$Δ$, $Δ(1600) \to N^*(1440)π$, $Δ(1600) \to Δπ$ and $Δ(1620) \to Δπ$ are found. In the near-threshold region, sizeable contributions from $Δ\to Δπ$, $Δ\to Nπ$, $N \to Δπ$ and nucleon pole are also indicated. Although these results are similar to those for $pN\to NNππ$ reactions, the antinucleon-nucleon collisions are shown to be complementary to the nucleon-nucleon collisions and may even have advantages in some aspects. The PANDA/FAIR experiment is suggested to be an excellent place for studying the properties of relevant $N^*$ and $Δ^*$ resonances.

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arXiv2010

Contribution of the t-channel $N^*(1535)$ exchange for the $p\bar p \to ϕϕ$ reaction

Since the $N^*(1535)$ resonance was found to have large coupling to the strangeness due to its possible large $s\bar s$ component, we investigate the possible contribution of the t-channel $N^*(1535)$ exchange for the $p\bar p \to ϕϕ$ reaction. Our calculation indicates that the new mechanism gives very significant contribution for the energies above 2.25 GeV and may be an important source for evading the Okubo-Zweig-Iizuka rule in the $ϕ$ production from $N \bar{N}$ annihilation.

hep-ph↗

arXiv2010

Double pion production in $NN$ and $\bar{N}N$ collisions

With an effective Lagrangian approach, we give a full analysis on the $NN \to NNππ$ and $\bar{N}N\to \bar{N}Nππ$ reactions by exploring the roles of various resonances with mass up to 1.72 GeV. We find large contributions from $Δ$, $N^*(1440)$, $Δ(1600)$ and $Δ(1620)$ resonances. Our calculations also indicate sizeable contributions from nucleon poles for the energies close to the threshold. A good description to the existing data of different isospin channels of $NN\to NNππ$ and $\bar{N}N\to \bar{N}Nππ$ for beam energies up to 2.2 GeV is reached. Our results provide important implications to the ABC effect and guildlines to the future experimental projects at COSY, HADES and HIRFL-CSR. We point out that the PANDA at FAIR could be an essential place for studying the properties of baryon resonances and the data with baryon and anti-baryon in final states are worth analyzing.

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arXiv2010

Partial wave analysis of $ψ'\toγχ_{c0}\to γp K^- \barΛ$ used for searching for baryon resonance

The abundant $ψ'$ events have been collected at the Beijing Electron Positron Collider-II (BEPCII) that could undoubtedly provide us with a great opportunity to study the more attractive charmonium decays. As has been noticed before, in the process of $J/ψ$ decaying to the baryonic final states, $p K^- \barΛ$, the evident $Λ^*$ and $N^*$ bands have been observed. Similarly, by using the product of $χ_{cJ}$ from $ψ'$ radiative decay, we may confirm it or find some extra new resonances. $χ_{c0}$'s data samples will be more than $χ_{c1,2}$ taking into account the larger branching ratio of $ψ'\toγχ_{c0}$. Here, we provide explicit partial wave analysis formulae for the very interesting channel $ψ'\toγχ_{c0}\to γp K^- \barΛ$.

hep-ph↗

arXiv2010

Phenomenological analysis of the double pion production in nucleon-nucleon collisions up to 2.2 GeV

With an effective Lagrangian approach, we analyze several NN \to NNππchannels by including various resonances with mass up to 1.72 GeV. For the channels with the pion pair of isospin zero, we confirm the dominance of N*(1440)\to Nσin the near threshold region. At higher energies and for channels with the final pion pair of isospin one, we find large contributions from N*(1440)\to Δπ, double-Delta, Δ(1600) \to N*(1440)π, Δ(1600) \to Δπand Δ(1620) \to Δπ. There are also sizeable contributions from Δ\to Δπ, Δ\to Nπ, N \to Δπand nucleon pole at energies close to the threshold. We well reproduce the total cross sections up to beam energies of 2.2 GeV except for the pp\to ppπ^0π^0 channel at energies around 1.1 GeV and our results agree with the existing data of differential cross sections of pp \to ppπ^+π^-, pp \to nnπ^+π^+ and pp \to ppπ^0π^0 which are measured at CELSIUS and COSY.

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arXiv2009

Strong decays of $N^{*}(1535)$ in an extended chiral quark model

The strong decays of the $N^{*}(1535)$ resonance are investigated in an extended chiral quark model by including the low-lying $qqqq\bar{q}$ components in addition to the $qqq$ component. The results show that these five-quark components in $N^{*}(1535)$ contribute significantly to the $N^{*}(1535)\to Nπ$ and $N^{*}(1535)\to Nη$ decays. The contributions to the $Nη$ decay come from both the lowest energy and the next-to-lowest energy five-quarks components, while the contributions to the $Nπ$ decay come from only the latter one. Taking these contributions into account, the description for the strong decays of $N^{*}(1535)$ is improved, especially, for the puzzling large ratio of the decays to $Nη$ and $Nπ$.

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arXiv2009

Strangeness production from pp collisions

The study of the strangeness production from pp collisions plays important roles in two aspects: exploring the properties of baryon resonances involved and understanding the strangeness production from heavy ion collisions to explore the properties of high energy and high density nuclear matter. Here we review our recent studies on several most important channels for the strangeness production from pp collisions. The previously ignored contributions from Delta*(1620) and N*(1535) resonances are found to play dominant role for the pp --> n K+ Sigma+, pp --> pK+ Lambda and pp --> pp phi reactions near-thresholds. These contributions should be included for further studies on the strangeness production from both pp collisions and heavy ion collisions.

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arXiv2009

Evidence of N*(1535) resonance contribution in the pn->dϕreaction

The N*(1535) resonance contributions to the pn->dϕreaction are evaluated in an effective Lagrangian model. The π-, η-, and ρ-meson exchange are considered. It is shown that the contributions from π- and ρ-meson exchange are dominant, while the contribution from η-meson exchange is negligibly small. Our theoretical results reproduce the experimental data of both total cross section and angular distribution well. This is another evidence that the N*(1535) resonance has large s\bar{s} component leading to a large coupling to Nϕ, which may be the real origin of the OZI rule violation in the \piN and pN reactions.

nucl-th↗

arXiv2009

Role of the N*(1440) resonance in the pp->pnpi+ reaction

New measurement by CELSIUS-WASA Collaboration on the pp->pn pi+ reaction reveals clear evidence for the presence of the Roper resonance N*(1440) which has been ignored in previous theoretical calculations. In this article, based on an effective Lagrangian approach and available knowledge on the Roper resonance, we investigate the role of the Roper resonance for the pp->pn pi+ reaction. It is found that the contribution from the Roper resonance N*(1440) becomes significant for kinetic energy above 1.1 GeV, consistent with the new experimental observation. The t-channel sigma-meson exchange is dominant for the production of the Roper resonance.

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arXiv2008

Coupling Constant for $\mathbf{N^*(1535)Nρ}$

The value of the $N^*(1535)Nρ$ coupling constant $g_{N^*Nρ}$ derived from the $N^*(1535) \to Nρ\to N ππ$ decay is compared with that deduced from the radiative decay $N^*(1535) \to N γ$ using the vector-meson-dominance model. On the basis of an effective Lagrangian approach, we show that the value of $g_{N^*Nρ}$ extracted from the available experimental data on the two decays are consistent, though the error bars are rather large.

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arXiv2007

On $pp \to p K Λ, N K Σ, pp ϕ$ -- the basic ingredients for strangeness production in heavy ion collisions

The strangeness production in heavy ion collisions was proposed to be probes of the nuclear equation of state, Kaon potential in nuclear medium, strange quark matter and quark-gluon plasma, etc. However, to act as reliable probes, proper understanding of the basic ingredients for the strangeness production, such as $pp \to pK^+Λ$, $pp \to pp ϕ$ and $pp \to nK^+Σ^+$ is necessary. Recent study of these reactions clearly shows that previously ignored contributions from the spin-parity $1/2^-$ resonances, $N^*(1535)$ and $Δ^*(1620)$, are in fact very important for these reactions, especially for near-threshold energies. It is necessary to include these contributions for getting reliable calculation for the strangeness production in heavy ion collisions.

nucl-th↗

arXiv2007

Role of t-channel meson exchange in S-wave pi N and K N scattering

The low-energy S-wave pi N and K N scatterings are studied by the K-matrix approach within the meson exchange framework. The t-channel meson exchanges, especially rho and sigma exchanges, are found to play a very important role in these two processes. The t-channel rho exchange determines the isospin structure of the scattering amplitudes, it gives attractive force in the low isospin state but repulsive force in the high isospin state. The t-channel sigma exchange gives a very large contribution in these two processes, while it is negligible in meson-meson S-wave scatterings.

hep-ph↗

arXiv2007

Isospin violation in $ϕ, J/ψ, ψ^\prime \to ωπ^0$ via hadronic loops

In this work, we study the isospin-violating decay of $ϕ\to ωπ^0$ and quantify the electromagnetic (EM) transitions and intermediate meson exchanges as two major sources of the decay mechanisms. In the EM decays, the present datum status allows a good constraint on the EM decay form factor in the vector meson dominance (VMD) model, and it turns out that the EM transition can only account for about $1/4\sim 1/3$ of the branching ratio for $ϕ\to ωπ^0$. The intermediate meson exchanges, $K\bar{K}(K^*)$ (intermediate $K\bar{K}$ interaction via $K^*$ exchanges), $K\bar{K^*}(K)$ (intermediate $K\bar{K^*}$ rescattering via kaon exchanges), and $K\bar{K^*}(K^*)$ (intermediate $K\bar{K^*}$ rescattering via $K^*$ exchanges), which evade the naive Okubo-Zweig-Iizuka (OZI) rule, serve as another important contribution to the isospin violations. They are evaluated with effective Lagrangians where explicit constraints from experiment can be applied. Combining these three contributions, we obtain results in good agreement with the experimental data. This approach is also extended to $J/ψ(ψ^\prime)\to ωπ^0$, where we find contributions from the $K\bar{K}(K^*)$, $K\bar{K^*}(K)$ and $K\bar{K^*}(K^*)$ loops are negligibly small, and the isospin violation is likely to be dominated by the EM transition.

hep-ph↗

arXiv2007

Baryon spectra and non-strange baryon strong decays in the chiral SU(3) quark model

In the framework chiral SU(3) quark model, the baryon spectra within the band of $N\leq 2$ are studied, and the effect of the confining potential in different configurations, namely the $Δ$-mode and Y-mode are compared. In the same way, the baryon spectra in the extended chiral SU(3) quark model, in which additional vector meson exchanges are introduced, are also calculated. It is shown that a reasonable baryon spectrum in the chiral SU(3) quark model can be achieved no matter whether the $Δ$-mode or the Y-mode confining potential is employed. In the extended chiral SU(3) quark model, several energy levels are further improved. The resultant binding energies of excited baryon states in different confining modes deviate just by a few to several tens MeV, and it is hard to justify which confining mode is the dominant one. The non-strange baryon strong decay widths are further discussed in the point-like meson emission model by using the wave-function obtained in the spectrum calculation. The resultant widths can generally explain the experimental data but still cannot distinguish which confining mode is more important in this simple decay mode.

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