arXiv subjects

Pengnian Shen

Publications and source records attributed to Pengnian Shen.

11 recordsLinked to original sources

arXiv2022

Possible dibaryon production at $\bar{\rm{P}}$anda with a Lagrangian approach

In order to confirm the existence of the dibaryon state $d^*(2380)$ observed at WASA@COSY, we estimate the production of the possible dibaryon and anti-dibaryon pair $d^*\bar{d}^*$ at the energy region of the upcoming experiments at $\bar{\rm{P}}$anda. Based on some qualitative properties of $d^*$ extracted from the analysez in the non-relativistic quark model, the production cross section for this spin-3 particle pair are calculated with the help of an phenomenological effective relativistic and covariant Lagrangian approach.

hep-ph↗

arXiv2020

Selected strong decays of pentaquark State $P_c(4312)$ in a chiral constituent quark model

The newly confirmed pentaquark state $P_c(4312)$ has been treated as a weakly bound $(Σ_c\bar{D})$ state by a well-established chiral constituent quark model and by a dynamical calculation on quark degrees of freedom where the quark exchange effect is accounted for. The obtained mass $4308$ MeV agrees with data. In this work, the selected strong decays of the $P_c(4312)$ state are studied with the obtained wave function. It is shown that the width of the $Λ_c\bar{D}^*$ decay is overwhelmed and the branching ratios of the $p\,η_c$ and $p\,J/ψ$ decays are both less than 1 percentage.

hep-ph↗

arXiv2019

Photo-absorption on deuteron contributed by d^*(2380) resonance

In order to understand the possible physical nature of the newly observed resonance $d^*(2380)$, we calculate the real photo-absorption cross section on deuteron contributed by the resonance $d^*(2380)$ by considering the electromagnetic transition amplitude of $γ+d\rightarrow d^*(2380)$. In our interpretation, the $d^*(2380)$ is regarded as a compact six-quark system with mainly two components of $ΔΔ$ and hidden-color clusters $C_8C_8$. We find that only the next-to-leading terms contribute the $γ+d\rightarrow d^*(2380)$ and the obtained photo-absorption cross section is quite small which is in the order of 10 $nb$. Compared with data measured at ELPH and Mainz recently, it is almost about 20 times smaller.

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arXiv2018

On the form factors of $d^*(2380)$

In order to explore the possible physical quantities for judging different structures of the newly observed resonance $d^*(2380)$, we study its electromagnetic form factors. In addition to the electric charge monopole $C0$, we calculate its electric quadrupole $E2$, magnetic dipole $M1$, and six-pole $M3$ form factors on the base of the realistic coupled $ΔΔ+CC$ channel $d^*$ wave function with both the $S$- and $D$-partial waves. The results show that the magnetic dipole moment and electric quadrupole deformation of $d^*$ are 7.602 and $2.53\times 10^{-2}~\rm{fm}^2$, respectively. The calculated magnetic dipole moment in the naive constituent quark model is also compared with the result of $D_{12}π$ picture. By comparing with partial results where the $d^*$ state is considered with a single $ΔΔ$ and with a $D_{12}π$ structures, we find that in addition to the charge distribution of $d^*(2380)$, the magnetic dipole moment and magnetic radius can be used to discriminate different structures of $d^*$. Moreover, a quite small electric quadrupole deformation indicates that $d^*$ is more inclined to an slightly oblate shape due to our compact hexaquark dominated structure of $d^*(2380)$.

hep-ph↗

arXiv2017

On the charge distribution of $d^*(2380)$

We calculate the charge distributions of $d^*(2380)$. Two different interpretations of the $d^*$ are considered for a comparison. One is a compact explanation with coupled $ΔΔ+CC$ two-channel approximation in the chiral constituent quark model. Another is a resonance state of $D_{12}π$. The remarkable differences of the charge distributions in the two pictures are shown and it is expected that the future experiments may provide a clear test for the different theoretical interpretations.

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arXiv2017

Decay width of $d^*(2380) \to NN π$ process in a chiral constituent quark model

The width of three-body single-pion decay process $d^*\to NNπ^{0,\pm}$ is calculated by using the $d^*$ wave function obtained from our chiral SU(3) constituent quark model calculation. The effect of the dynamical structure on the width of $d^*$ is taken into account in both the single $ΔΔ$ channel and coupled $ΔΔ+CC$ two-channel approximations. Our numerical result shows that in the coupled-channel approximation, namely, the hidden-color configuration being considered, the obtained partial decay width of $d^*\to NNπ$ is about several hundred $\rm {KeV}$, while in the single $ΔΔ$ channel it is just about $2\sim 3~\rm{MeV}$. We, therefore, conclude that the partial width in the single-pion decay process of $d^*$ is much smaller than the widths in its double-pion decay processes. Our prediction may provide a criterion for judging different interpretations of the $d^*$ structure, as different pictures for the $d^*$ may result quite different partial decay width.

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arXiv2016

Decay width of $d^*(2380)\to NN ππ$ processes

The decay widths of four-body double-pion decays $\ds\to pn π^0π^0$, $\ds\to pn π^+π^-$, and iso-scalar parts of $\ds\to pp π^0π^-$ and $\ds\to nn π^+π^0$ are explicitly calculated with the help of the $d^*$ wave function obtained in a chiral SU(3) quark model calculation. The effect of the dynamical structure on $\ds$'s width is analyzed both in the single $ΔΔ$ channel and coupled $ΔΔ$ and $CC$ channel approximations. It is found that in the coupled-channel approximation, the obtained partial decay widths of $\ds\to pn π^0π^0$, $\ds\to pn π^+π^-$, and those of $d^*$ to the iso-scalar parts of $pp π^0π^-$ and $nn π^+π^0$ are about $7.4$MeV, $16.4$MeV, $3.5$MeV and $3.5$MeV, respectively As a consequence, the total width is about $64.5$MeV. These widths are consistent with those estimated by using the corresponding cross section data in our previous investigation and also the observed data. But in the single $ΔΔ$ channel approximation, the widths are still almost 2-times larger than the measured values. Apparently, the explicitly calculated width together with the evaluated mass of $d^*$ in the coupled $ΔΔ$ and $CC$ channel approximation can well explain the observed data, which again supports our assertion that the $\ds$ resonance is a six-quark dominated exotic state.

hep-ph↗

arXiv2015

A study of $d^*(2380)\to d ππ$ decay width

The decay widths of the $\ds\to d π^0π^0$ and $\ds\to d π^+π^-$ processes are explicitly calculated in terms of our chiral quark model. By using the experimental ratios of cross sections between various decay channels, the partial widths of the $\ds\to pn π^0π^0$, $\ds\to pn π^+π^-$, $\ds\to pp π^0π^-$, and $\ds\to nn π^+π^0$ channels are also extracted. Further including the estimated partial width for the $\ds\to pn $ process, the total width of the $\ds$ resonance is obtained. In the first step of the practical calculation, the effect of the dynamical structure on the width of $\ds$ is studied in the single $ΔΔ$ channel approximation. It is found that the width is reduced by few tens of MeV, in comparison with the one obtained by considering the effect of the kinematics only. This presents the importance of such effect from the dynamical structure. However, the obtained width with the single $ΔΔ$ channel wave function is still too large to explain the data. It implies that the $\ds$ resonance will not consist of the $ΔΔ$ structure only, and instead there should be enough room for other structure such as the hidden-color (CC) component. Thus, in the second step, the width of $\ds$ is further evaluated by using a wave function obtained in the coupled $ΔΔ$ and CC channel calculation in the framework of the Resonating Group Method (RGM). It is shown that the resultant total width for $\ds$ is about 69 MeV, which is compatible with the experimental observation of about 75 MeV and justifies our assertion that the $\ds$ resonance is a hexaquark-dominated exotic state.

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arXiv2008

Hypernucleus Production by $A(p,pK^+)_ΛB$ Reactions

The $Λ$-hypernucleus production by $A(p, pK^+)_ΛB$ reactions is investigated within the framework of the distorted wave impulse approximation(DWIA). The amplitude for the elementary process is evaluated in a fully covariant two-nucleon model based on the effective Lagrangian. The reaction cross sections for $Λ$-hypernucleus productions on $^6Li$, $^{12}C$ and $^{16}O$ targets are calculated. It is found that the distortion effects tend to reduce the cross sections by a factor of 3$\sim$10. Various differential cross sections (DCS) and double differential cross sections (DDCS) are presented. It is shown that for the $s_Λ-$wave hypernucleus production, the DCS is decreased with increasing nuclear mass, and the DCS for the $p_Λ-$wave hypernucleus production is normally higher than that for the $s_Λ-$wave hypernucleus production. As a reference, the DDCS with respect to the momenta of the outgoing proton and kaon is also demonstrated. Finally, the missing mass spectra of the inclusive reaction $p+A\to p+ K^+ + X$ for $^6Li$, $^{12}C$ and $^{16}O$ targets are presented, from which the masses of hypernuclei can accurately be extracted. Thus, we conclude that the missing mass spectrum method is an alternative to study hypernuclear physics. And the study of hypernuclear physics can be carried out in COSY and CSR by the $A(p,pK^+)_ΛB$ reaction due to the $μ$b-order reaction cross sections.

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arXiv2004

Single and Double Peripheral Production of Sigmas in Proton Proton Collisions

The Pomeron, which dominates high energy elastic and diffractive hadronic processes, must be largely gluonic in nature. We use a recent picture of a scalar glueball/sigma system with coupling of the sigma to glue determined from experiment to predict strong peripheral sigma production in the pp$π^0π^0$ and double sigma production in the pp$π^0π^0π^0π^0$ channels.

hep-ph↗

arXiv2000

Peripheral Production of Sigmas in Proton Proton Collisions

hep-ph↗