Search

The $p p \to n K^+ ��^+(1385)$ reaction is a very good isospin $3/2$ filter for studying $��^{++*}$ resonance decaying to $K^+��^+(1385)$. Within the effective Lagrangian method, we investigate the $��(1385)$ (spin-parity $J^P = 3/2^+$) hadronic production in the $��^+ p \to K^+ ��^+(1385)$ and $p p \to n K^+ ��^+(1385)$ reactions. For $��^+ p \to K^+ ��^+(1385)$ reaction, in addition to the "background" contributions from $t$-channel $K^{*0}$ exchange, $u$-channel $��(1115)$ and $��^0(1193)$ exchange, we also consider the contribution from the $s$-channel $��^*(1940)$ resonance, which has significant coupling to $K��(1385)$ channel. We show that the inclusion of the $��^*(1940)$ resonance leads to a fairly good description of the low energy experimental total cross section data of $��^+ p \to K^+ ��^+(1385)$ reaction. Basing on the study of $��^+ p \to K^+��^+(1385)$ reaction and with the assumption that the excitation of $��^*(1940)$ resonance dominant the $pp \to n K^+ ��^+(1385)$ reaction, we calculate the total and differential cross sections of $p p \to n K^+ ��^+(1385)$ reaction. It is shown that the new experimental data support the important role played by the $��^*(1940)$ resonance with a mass in the region of $1940$ MeV and a width of around $200$ MeV. We also demonstrate that the invariant mass distribution and the Dalitz Plot provide direct information of the $��^+(1385)$ production, which can be tested by future experiments., Published in Phys. Rev. C. arXiv admin note: substantial text overlap with arXiv:1302.0468

Within the framework of the effective Lagrangian approach, we perform a thorough analysis of the $J/��\to P��(��^*)$, $J/��\to VP$, $V\to P��(��^*)$, $P\to V��(��^*)$ and $P\to����(��^*)$ processes, where $V$ stand for light vector resonances, $P$ stand for light pseudoscalar mesons, and $��^*$ subsequently decays into lepton pairs. The processes with light pseudoscalar mesons $��$ and $��'$ are paid special attention to and the two-mixing-angle scheme is employed to describe their mixing. The four mixing parameters both in singlet-octet and quark-flavor bases are updated in this work. We confirm that the $J/��\to ��(��^{\prime})��^{(*)}$ processes are predominantly dominated by the $J/��\to ��_c ��^{*} \to ��(��^{\prime})��^{(*)}$ mechanism. Predictions for the $J/��\to P ��^+��^-$ are presented. A detailed discussion on the interplay between electromagnetic and strong transitions in the $J/��\to VP$ decays is given., 29 pages, 8 figures and 6 tables. References added. Accepted by Phys.Rev.D

The $��p \to ��p ��^0$ reaction near threshold is studied within an effective Lagrangian method. The production process is described by single-pion and single-kaon exchange. In addition to the role played by the $��^*(1385)$ resonance of spin-parity $J^P = 3/2^+$, the effects of a newly proposed $��^*$ ($J^P = 1/2^-$) state with mass and width around $1380$ MeV and $120$ MeV are investigated. We show that our model leads to a good description of the experimental data on the total cross section of the $��p \to ��p ��^0$ reaction by including the contributions from the possible $��^*(\frac{1}{2}^-)$ state. However, the theoretical calculations by considering only the $��^*(1385)$ resonance fail to reproduce the experimental data, especially for the enhancement close to the reaction threshold. On the other hand, it is found that the single-pion exchange is dominant. Furthermore, we also demonstrate that the angular distributions provide direct information of this reaction, hence could be useful for the investigation of the existence of the $��^*(\frac{1}{2}^-)$ state and may be tested by future experiments., 8 pages, 5 figures

By using an effective Lagrangian method, we study the effects of a newly proposed $\Sigma^*(1/2^-)$ state with mass around 1380 MeV in the initial-state polarized $\gamma N\rightarrow K^{+} \Sigma^*(1385) \rightarrow K^{+} \pi \Lambda$ process near threshold. The theoretical predictions for the helicity cross sections $\sigma_{3/2}$, $\sigma_{1/2}$ as well as their ratios, and the angular distributions of $\pi$ in the $\pi\Lambda$ center-of-mass system are given. It is found that assuming $\Sigma^*(1/2^-)$ exists or not, these physical quantities are distinctly different. So our results could be useful for the investigation of the existence of $\Sigma^*(1/2^-)$ when the experimental data are available in the future., Comment: version published in PRC, 16 pages, 5 figures, more comments added

In the present work, we apply the one-boson-exchange potential (OBEP) model to investigate the possibility of Y(2175) and $\eta(2225)$ as bound states of $\Lambda\bar{\Lambda}(^3S_1)$ and $\Lambda\bar{\Lambda}(^1S_0)$ respectively. We consider the effective potential from the pseudoscalar $\eta$-exchange and $\eta^{'}$-exchange, the scalar $\sigma$-exchange, and the vector $\omega$-exchange and $\phi$-exchange. The $\eta$ and $\eta^{'}$ meson exchange potential is repulsive force for the state $^1S_0$ and attractive for $^3S_1$. The results depend very sensitively on the cutoff parameter of the $\omega$-exchange ($\Lambda_{\omega}$) and least sensitively on that of the $\phi$-exchange ($\Lambda_{\phi}$). Our result suggests the possible interpretation of Y(2175) and $\eta(2225)$ as the bound states of $\Lambda\bar{\Lambda}(^3S_1)$ and $\Lambda\bar{\Lambda}(^1S_0)$ respectively.

By using an effective Lagrangian method, we study the effects of a newly proposed $��^*(1/2^-)$ state with mass around 1380 MeV in the initial-state polarized $��N\rightarrow K^{+} ��^*(1385) \rightarrow K^{+} ����$ process near threshold. The theoretical predictions for the helicity cross sections $��_{3/2}$, $��_{1/2}$ as well as their ratios, and the angular distributions of $��$ in the $����$ center-of-mass system are given. It is found that assuming $��^*(1/2^-)$ exists or not, these physical quantities are distinctly different. So our results could be useful for the investigation of the existence of $��^*(1/2^-)$ when the experimental data are available in the future., version published in PRC, 16 pages, 5 figures, more comments added

In this work we make a systematic analysis of the correlated processes $J/\psi\to \gamma \eta(1440)/f_1(1420)$ with $\eta(1440)/f_1(1420)\to K\bar{K}\pi$, $\eta\pi\pi$ and $3\pi$, 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 $\pi\pi$ invariant mass spectrum of $\eta(1440)\to 3\pi$ with anomalously large isospin violations. Nevertheless, we explicitly demonstrate that the TSM can produce obvious peak position shifts for the same $\eta(1440)$ or $f_1(1420)$ state in different decay channels. This is a strong evidence that the $\eta(1405)$ and $\eta(1475)$ are actually the same state, i.e. $\eta(1440)$. We also make an analysis of the radiative decays of $\eta(1440)\to \gamma V$ ($V=\phi$, $\rho^0$ or $\omega$) 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 $\eta(1405)$ and $\eta(1475)$., Comment: Revtex, 17 pages and 7 eps figures; revised version to appear in PRD

We calculate the correction to the two-gluon decay width due to the finite extension of the vertex function. We obtain the corrected factor to the zero-range vertex gamma = 1.32, gamma = 1.45, gamma = 1.26 for eta(c),chi(c0), and chi(c2), respectively. With the decay width Gamma(eta(c) --> 2g) we extract the value alpha(s)(m(c)) = 0.28 +/- 0.05 which agrees with that calculated from the same correction to the process Gamma(J/Psi --> 3g). This correction to the process Gamma(eta(c) --> 2g) is not as large as that to the process Gamma(J/Psi --> 3g).

The resonances ($\eta_c,\chi_{c0,c2}$) 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 $\chi_{c2}$, which are dependent on the unknown phases $\phi_{E,M}$ 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 $\sqrt{s} \sim M_{\chi_{c2}}$ for most $\phi_{E,M}$., Comment: 8 pages, 6 figures; a global factor in the calculation is corrected

Based on the effective Lagrangian approach, the $ J/\psi \to p \bar{p} \phi$ decay is studied in an isobar resonance model with the assumption that the $\phi$-meson is produced from intermediate nucleon resonances. The contributions from the $N^*_{1/2^-}(1535)$, $N^*_{3/2^+}(1900)$, $N^*_{1/2^-}(2090)$ and $N^*_{1/2^+}(2100)$ states are considered. In terms of the coupling constants $g^{2}_{\phi N N^{*}}$ and $g^{2}_{\phi N N^{*}}$ extracted from the data of the partial decay widths of the $N^*$s to the $N\pi$ channel, the reaction cross section of the $\pi^{-}p\rightarrow n\phi$ process and the partial decay widths of the $J/\psi\rightarrow p\bar{p}\eta$ and $J/\psi\rightarrow p\bar{n}\pi^{-}$ processes, respectively, the invariant mass spectrum and the Dalitz plot for $ J/\psi \to p \bar{p} \phi$ are predicted. It is shown that there are two types of results. In the type I case, a large peak structure around 2.09GeV implies that a considerable mount of $N\phi$ or $qqqs\bar s$ component may exist in the narrow-width $N^*_{1/2^-}(2090)$ state, but for the wide-width $N^*_{1/2^+}(2100)$ state, it has little $qqqs\bar s$ component. In the type II case, a small peak around 2.11GeV may only indicate the existence of a certain mount of $p\phi$ or $qqqs\bar s$ component in the narrow-width $N^*_{1/2^+}(2100)$ state, but no information for the wide-width $N^*_{1/2^-}(2090)$ state. Further BESIII data with high statistics would help us to distinguish the strange structures of these $N^*$s.

The BES-III Collaboration recently report the observation of anomalously large isospin violations in $J/\psi\to \gamma\eta(1405/1475) \to \gamma \pi^0 f_0(980)\to \gamma +3\pi$, where the $f_0(980)$ in the $\pi\pi$ 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 $\eta(1405/1475)\to a_0(980)\pi$ and $K\bar{K}^*+c.c.$, which can possibly explain the long-standing puzzle about the need for two close states $\eta(1405)$ and $\eta(1475)$ in $\eta\pi\pi$ and $K\bar{K}\pi$, respectively. The TS could be a key to our understanding of the nature of $\eta(1405/1475)$ and advance our knowledge about the mixing between $a_0(980)$ and $f_0(980)$., Comment: 4 pages and 7 eps figures; Journal-matched version

Based on the effective Lagrangian approach, the $ J/��\to p \bar{p} ��$ decay is studied in an isobar resonance model with the assumption that the $��$-meson is produced from intermediate nucleon resonances. The contributions from the $N^*_{1/2^-}(1535)$, $N^*_{3/2^+}(1900)$, $N^*_{1/2^-}(2090)$ and $N^*_{1/2^+}(2100)$ states are considered. In terms of the coupling constants $g^{2}_{��N N^{*}}$ and $g^{2}_{��N N^{*}}$ extracted from the data of the partial decay widths of the $N^*$s to the $N��$ channel, the reaction cross section of the $��^{-}p\rightarrow n��$ process and the partial decay widths of the $J/��\rightarrow p\bar{p}��$ and $J/��\rightarrow p\bar{n}��^{-}$ processes, respectively, the invariant mass spectrum and the Dalitz plot for $ J/��\to p \bar{p} ��$ are predicted. It is shown that there are two types of results. In the type I case, a large peak structure around 2.09GeV implies that a considerable mount of $N��$ or $qqqs\bar s$ component may exist in the narrow-width $N^*_{1/2^-}(2090)$ state, but for the wide-width $N^*_{1/2^+}(2100)$ state, it has little $qqqs\bar s$ component. In the type II case, a small peak around 2.11GeV may only indicate the existence of a certain mount of $p��$ or $qqqs\bar s$ component in the narrow-width $N^*_{1/2^+}(2100)$ state, but no information for the wide-width $N^*_{1/2^-}(2090)$ state. Further BESIII data with high statistics would help us to distinguish the strange structures of these $N^*$s.

We discuss the moment analysis method for the 0(++) and 2(++) coupling mode of f(J)(1710) for incomplete phase space in the radiative decay J/psi --> gammaK(+)K(-), and give a new formulation of analysing the f(J)(1710) structure for the Beijing Spectrometer detector at the Beijing Electron-Positron Collider. The incomplete detection phase space results in a significant effect on the moment analysis.

We extend our recent phenomenological study of $pN \to NN\pi\pi$ reactions to the $\bar{p}N \to \bar{N}N\pi\pi$ reactions for anti-proton beam momenta up to 3.0 GeV within an effective Lagrangian approach. The contribution of $N^*(1440)$ with its $N\sigma$ decay mode is found to be dominant at the energies close to threshold for $\bar NN\pi^+\pi^-$ and $\bar NN\pi^0\pi^0$ channels. At higher energies or for $p\bar n\pi^-\pi^-$ and $\bar NN\pi^\pm\pi^0$ channels where $N^*(1440)\to N\sigma$ mode cannot contribute, large contributions from double-$\Delta$, $\Delta(1600) \to N^*(1440)\pi$, $\Delta(1600) \to \Delta\pi$ and $\Delta(1620) \to \Delta\pi$ are found. In the near-threshold region, sizeable contributions from $\Delta \to \Delta\pi$, $\Delta \to N\pi$, $N \to \Delta\pi$ and nucleon pole are also indicated. Although these results are similar to those for $pN\to NN\pi\pi$ 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 $\Delta^*$ resonances., Comment: 14 pages+7 figures

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 $p\bar p \to \phi\phi$ 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 $\phi$ production from $N \bar{N}$ annihilation., Comment: 6 pages, 3 figures

The abundant $��'$ 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 $J/��$ decaying to the baryonic final states, $p K^- \bar��$, the evident $��^*$ and $N^*$ bands have been observed. Similarly, by using the product of $��_{cJ}$ from $��'$ radiative decay, we may confirm it or find some extra new resonances. $��_{c0}$'s data samples will be more than $��_{c1,2}$ taking into account the larger branching ratio of $��'\to����_{c0}$. Here, we provide explicit partial wave analysis formulae for the very interesting channel $��'\to����_{c0}\to ��p K^- \bar��$., 7 pages, 1 figure, version in Chin.Phys.C

The N*(1535) resonance contributions to the pn->d��reaction are evaluated in an effective Lagrangian model. The ��-, ��-, and ��-meson exchange are considered. It is shown that the contributions from ��- and ��-meson exchange are dominant, while the contribution from ��-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 N��, which may be the real origin of the OZI rule violation in the \piN and pN reactions., 13 pages,4 figures

The authors examine the contributions of the conventional sequential mechanism and the pion absorption-emission mechanism for the double charge exchange (DCX) on calcium isotopes. It is shown that by combining these two mechanisms the experimental data for the double isobaric analogue transitions can be reproduced quite well. The predictions for the low energy GS to GS DCX on calcium isotopes are presented.

In this work, we study the isospin-violating decay of phi-->omegapi0 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 model, and it turns out that the EM transition can only account for about 1/4~1/3 of the branching ratio for phi-->omegapi0. The intermediate meson exchanges, K[overline K](K*) (intermediate K[overline K] interaction via K* exchanges), K[overline K]*(K) (intermediate K[overline K]* rescattering via kaon exchanges), and K[overline K]*(K*) (intermediate K[overline K]* rescattering via K* exchanges), which evade the naive Okubo-Zweig-Iizuka 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/psi(psi[prime])-->omegapi0, where we find contributions from the K[overline K](K*), K[overline K]*(K), and K[overline K]*(K*) loops are negligibly small, and the isospin violation is likely to be dominated by the EM transition.

Within the framework of operator expansion approach for the pion absorption-emission mechanism of double charge exchange a summation over the leading terms of the infinite commutator series is performed. The contribution of highly excited states is estimated.

The two pure nucleonic mechanisms (the conventional sequential mechanism and the two-nucleon pion absorption-emission mechanism[1]) are studied within a unified framework of Distorted Wave Impulse Approximation (DWIA). The distorted pion waves are obtained by solving the Klein-Gordon equation with the first-order optical potential. The difference between this approach and the eikonal approximation is showed. For the two-nucleon pion absorption-emission mechanism the effective Landau-Migadal interaction of Pines, et al.[2] is used for the two bound nucleons, the result is compared with that by using the Paris force. By combining these two mechanism the 0° excitation functions for the DCX reactions to the isobaric analog states on the 14C, 18O, 26Mg and 42Ca are calculated and compared with the experimental data.

In this work, we study the isospin-violating decay of $��\to ����^0$ 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 $��\to ����^0$. 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 $J/��(��^\prime)\to ����^0$, 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., Revised version resubmitted to PRD; Additional loop contributions included; Conclusion unchanged

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., Comment: 11 pages, 3 figures

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 $pp \to pK^+��$, $pp \to pp ��$ and $pp \to nK^+��^+$ is necessary. Recent study of these reactions clearly shows that previously ignored contributions from the spin-parity $1/2^-$ resonances, $N^*(1535)$ and $��^*(1620)$, 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., 12 pages, 12 figures, Contributed to the proceedings of the International workshop on nuclear dynamics in heavy-ion reactions and neutron stars, July, 10-14, Beijing, China

We investigate the possibility of producing the enhancement observed in $J/��\to ��X$ with $X\to ����$ at BES by intermediate meson rescatterings through $f_0(1710)\to PP\to ����$, $f_0(1710)\to VV\to ����$, and $f_0(1710)\to SS\to ����$. We find that intermediate meson rescatterings can produce some enhancement near the $����$ threshold. Implications about the property of this enhancement are discussed., 12 pages, 6 figures; Version to appear in Phys. Rev. D

$K��$ $S$ wave scattering is studied using a chiral unitary approach (ChUT) taking into account coupled channels. With the amplitudes derived from the lowest order chiral Lagrangian as the kernel of a set of coupled channel Bathe-Salpeter equations, the $I=1/2$ $S$ wave $K��$ scattering phase shifts below 1.2 GeV can be fitted by one parameter, a subtraction constant, and a scalar resonance corresponding to the controversial $��$ ($K^*_0(800)$) can be generated dynamically. A good description of the $I=3/2$ $S$ wave $K��$ scattering phase shifts below 1.2 GeV can also be obtained. An artificial singularity in the conventional cut-off method of the 2-meson loop integral of the ChUT is found. The formalism is applied to deal with the $S$ wave $K��$ final state interaction (FSI) in the decay $J/��\to {\bar K}^{*0}(892)K^+��^-$, and a qualitatively good fit to the data is achieved. The role of $��$ in the decay is discussed., 23 pages, 6 figures; comparison with the results from the Roy equation analysis added. Version accepted for publication in Nucl. Phys. A

With accumulation of high statistics data at BES and CLEO-c, many new interesting channels can get enough statistics for partial wave analysis (PWA). Among them, $��\to ��p\bar p, ����\bar ��, ����\bar��, ����\bar ��$ channels provide a good place for studying baryon-antibaryon interactions; the double radiative decays $��\to����V$ with $V\equiv ��,��,��$ have a potential to provide information on the flavor content of any meson resonances (R) with positive charge parity ($C=+$) and mass above 1 GeV through $��\to��R \to����V$; $��(2S)\to����_{c0,1,2}$ with $��_{c0,1,2}\to K\bar K ��^+��^- $ and $2��^+2��^-$ decays are good processes to study $��_{cJ}$ charmonium decays. Using the covariant tensor formalism, here we provide theoretical PWA formulae for these channels., 20 pages

The double radiative decays $��\to����V$ with $V\equiv ��,��,��$ have a potential to provide information on the flavor content of any meson resonances (R) with positive charge parity ($C=+$) and mass above 1 GeV through $��\to��R \to����V$. To get the information, one needs both high statistic data and partial wave analysis (PWA). While high statistic data will be available soon at CLEO-c and BES-III, here we provide theoretical PWA formulae for these $��$ double radiative decay channels in the covariant tensor formalism., 9 pages, added references

Nucleon pole contributions in $J/��\to N \bar N ��$, $p \bar p ��$, $p \bar p ��^{\prime}$ and $p \bar{p} ��$ decays are re-studied. Different contributions due to PS-PS and PS-PV couplings in the $��$-N interaction and the effects of $NN��$ form factors are investigated in the $J/��\to N \bar N ��$ decay channel. It is found that when the ratio of $|F_0| /|F_M|$ takes small value, without considering the $NN��$ form factor, the difference between PS-PS and PS-PV couplings are negligible. However, when the $NN��$ form factor is included, this difference is greatly enlarged. The resultant decay widths are sensitive to the form factors. As a conclusion, the nucleon-pole contribution as a background is important in the $J/��\to N\bar{N}��$ decay and must be accounted. In the $J/��\to N\bar{N}��$ and $N\bar{N}��'$ decays, its contribution is less than 0.1% of the data. In the $J/��\to N\bar{N}��$ decay, it provides rather important contribution without considering form factors. But the contribution is suppressed greatly when adding the off-shell form factors. Comparing these results with data would help us to select a proper form factor for such kind of decay., 29 pages, 13 figures