arXiv subjects

P. N. Shen

Publications and source records attributed to P. N. Shen.

15 recordsLinked to original sources

arXiv2018

Phenomenological study on the decay widths of $Υ(nS)\rightarrow \bar{d}^{\ast}(2380)+X$

The decay widths of $Υ(nS)$ $\rightarrow$ $\bar{d}^{\ast}(2380)+X$ with $n=1,2,3$ are studied in a phenomenological way. With the help of crossing symmetry, the decay widths are obtained by investigating the imaginary part of the forward scattering amplitudes between $d^\ast$ and $Υ(nS)$. The wave functions of $d^\ast$ and deuteron obtained in previous studies are used for calculating the amplitude. The interaction between $d^{\ast}$ ($d$) and $Υ$ is governed by the quark-meson interaction where the coupling constant is determined by fitting the observed widths of $Υ(nS)$ $\rightarrow$ $\bar{d}+X$. The numerical results show that the decay widths of $Υ(nS)$ $\rightarrow$ $\bar{d}^{\ast}+X$ are about $2 - 10$ times smaller than that of $\bar{d}+X$. The calculated momentum of $\bar{d^*}$ is in the range $0.3-0.8$ GeV. Therefore, it is very likely that one can find $\bar{d}^\ast(2380)$ in these semi-inclusive decay processes.

hep-ph↗

arXiv2015

Understanding the structure of $d^*(2380)$ in chiral quark model

The structure and decay properties of $d^*$ have been detailedly investigated in both the chiral SU(3) quark model and the extended chiral SU(3) quark model that describe the energies of baryon ground states and the nucleon-nucleon (NN) scattering data satisfactorily. By performing a dynamical coupled-channels study of the system of $ΔΔ$ and hidden-color channel (CC) with quantum numbers $I(J^P)=0(3^+)$ in the framework of the resonating group method (RGM), we find that the $d^*$ has a mass of about $2.38-2.42$ GeV and a root-mean-square radius (RMS) of about $0.76-0.88$ fm. The channel wave function is extracted by a projection of the RGM wave function onto the physical basis, and the fraction of CC component in the $d^*$ is found to be about $66\%-68\%$, which indicates that the $d^*$ is a hexaquark-dominated exotic state. Based on this scenario the partial decay widths of $d^*\to d π^0 π^0$ and $d^*\to d π^+π^-$ are further explicitly evaluated and the total width is then obtained by use of the branching ratios extracted from the measured cross sections of other possible decay channels. Both the mass and the decay width of $d^*$ calculated in this work are compatible with the data ($M\approx 2380$ MeV, $Γ\approx 70$ MeV) reported by WASA-at-COSY Collaboration.

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arXiv2015

Is $d^*$ a candidate of hexaquark-dominated exotic state?

We confirm our previous prediction of a $d^*$ state with $I(J^P)=0(3^+)$ [Phys. Rev. C 60, 045203 (1999)] and report for the first time based on a microscopic calculation that $d^*$ is a hexaquark dominated exotic state as it has about 2/3 hidden color (CC) configurations. By performing a more elaborate dynamical coupled-channels investigation of the $ΔΔ$-CC system within the framework of resonating group method (RGM) in a chiral quark model, we found that the $d^*$ state has a mass of about 2.38-2.42 GeV, a root-mean-square radius (RMS) of 0.76-0.88 fm, and a CC fraction of 66%-68%. The last ensures that the $d^*$ has a rather narrow width which, together with the quantum numbers and our calculated mass, is consistent with the newly observed resonance-like structure ($M\approx 2380$ MeV, $Γ\approx 70$ MeV) in double-pionic fusion reactions reported by WASA-at-COSY Collaboration.

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arXiv2006

Color-flavor locked strangelets in a quark mass density-dependent model

The color-flavor locked (CFL) phase of strangelets is investigated in a quark mass density-dependent model. Parameters are determined by stability arguments. It is concluded that three solutions to the system equations can be found, corresponding, respectively, to positively charged, negatively charged, and nearly neutral CFL strangelets. The charge to baryon number of the positively charged strangelets is smaller than the previous result, while the charge of the negatively charged strangelets is nearly proportional in magnitude to the cubic-root of the baryon number. However, the positively charged strangelets are more stable compared to the other two solutions.

hep-ph↗

arXiv2005

Thermodynamics with density and temperature dependent particle masses and properties of bulk strange quark matter and strangelets

Thermodynamic formulas for investigating systems with density and/or temperature dependent particle masses are generally derived from the fundamental derivation equality of thermodynamics. Various problems in the previous treatments are discussed and modified. Properties of strange quark matter in bulk and strangelets at both zero and finite temperature are then calculated based on the new thermodynamic formulas with a new quark mass scaling, which indicates that low mass strangelets near beta equilibrium are multi-quark states with an anti-strange quark, such as the pentaquark (u^2d^2\bar{s}) for baryon nmber 1 and the octaquark (u^4d^3\bar{s}) for dibaryon etc.

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

Possible S-wave Dibaryons in SU(3) Chiral Quark Model

In the framework of the SU(3) chiral quark model, the $S-$wave baryon-baryon bound states are investigated. It is found that according to the symmetry character of the system and the contributions from chiral fields, there are three types of bound states. The states of the first type, such as $[ΩΩ]_{(0,0)}$ and $[Ξ^{*}Ω]_{(0,1/2)}$ are deeply bound dibaryon with narrow widths. The second type states, $[Σ^{*} Δ]_{(0,5/2)}$,$[Σ^{*} Δ]_{(3,1/2)}$, $[ΔΔ]_{(0,3)}$ and $[ΔΔ]_{(3,0)}$ are also bound states, but with broad widths. $[ΞΩ- Ξ^{*}Ω]_{(1,1/2)}$, $[ΞΞ]_{(0,1)}$, and $[N Ω]_{(2,1/2)}$ are third type states. They, like {\em d}, are weakly bound only if the chiral fields can provide attraction between baryons.

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arXiv2000

Dibaryon Systems In SU(3) Chira Quark Model

The possible candidates of $S-$wave dibaryons with various strange numbers are studied under the chiral SU(3) quark model. It is shown that there are three types of baryon-baryon bound states. The states of the first type are called deuteron-like states. If chiral fields can provide enough attraction between interacting baryons, these systems, such as $[ΞΩ- Ξ^{*}Ω]_{(1,1/2)}$, $[ΞΞ]_{(0,1)}$, $[N Ω]_{(2,1/2)}$ would be weakly bound. The states of the second type such as $[Σ^{*} Δ]_{(0,5/2)}$, $[Σ^{*} Δ]_{(3,1/2)}$, $[ΔΔ]_{(0,3)}$ and $[ΔΔ]_{(3,0)}$ are named as $ΔΔ$-like states. Due to the highly symmetric character in orbital space, these systems could be relatively deeply bound, but the strong decay modes of composed baryons cause the widths of the states much broader. The states of the third type are entitled as $ΩΩ$-like states. Due to the same symmetry character shown in the systems of the second type and the only weak decay mode of composed baryons, for instance in $[ΩΩ]_{(0,0)}$, or at most one strong decay mode of composed baryons, for example in $[Ξ^{*}Ω]_{(0,1/2)}$, these states are deeply bound states with narrow widths. The states of latter two types are most interesting new dibaryon states and should be carefully investigated both theoretically and experimentally.

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arXiv1999

Possible $ΔΔ$ dibaryons in the quark cluster model

In the framework of RGM, the binding energy of one channel $ΔΔ_{(3,0)}$($d^*$) and $ΔΔ_{(0,3)}$ are studied in the chiral SU(3) quark cluster model. It is shown that the binding energies of the systems are a few tens of MeV. The behavior of the chiral field is also investigated by comparing the results with those in the SU(2) and the extended SU(2) chiral quark models. It is found that the symmetry property of the $ΔΔ$ system makes the contribution of the relative kinetic energy operator between two clusters attractive. This is very beneficial for forming the bound dibaryon. Meanwhile the chiral-quark field coupling also plays a very important role on binding. The S-wave phase shifts and the corresponding scattering lengths of the systems are also given.

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arXiv1999

$NΩ$ and $ΔΩ$ dibaryons in SU(3) chiral quark model

The binding energy of the six quark system with strangeness s=-3 is investigated under the chiral SU(3) constituent quark model in the framework of $RGM$. The calculations of the single $NΩ$ channel with spin S=2 and the single $ΔΩ$ channel with spin S=3 are performed. The results show that both systems could be dibaryons and the interaction induced by the chiral field plays a very important role on forming bound states in the systems considered. The phase shifts and scattering lengths in corresponding channels are also given.

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arXiv1999

Possible Dibaryons with Strangeness s=-5

In the framework of $RGM$, the binding energy of the six quark system with strangeness s=-5 is systematically investigated under the SU(3) chiral constituent quark model. The single $Ξ^*Ω$ channel calculation with spins S=0 and 3 and the coupled $ΞΩ$ and $Ξ^*Ω$ channel calculation with spins S=1 and 2 are considered, respectively. The results show following observations: In the spin=0 case, $Ξ^* Ω$ is a bound dibaryon with the binding energy being $80.0 \sim 92.4 MeV$. In the S=1 case, $ΞΩ$ is also a bound dibaryon. Its binding energy is ranged from $26.2 MeV$ to $32.9 MeV$. In the S=2 and S=3 cases, no evidence of bound dibaryons are found. The phase shifts and scattering lengths in the S=0 and S=1 cases are also given.

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arXiv1999

H-Dihyperon in Quark Cluster Model

The H dihyperon (DH) is studied in the framework of the SU(3) chiral quark model. It is shown that except the $σ$ chiral field, the overall effect of the other SU(3) chiral fields is destructive in forming a stable DH. The resultant mass of DH in a three coupled channel calculation is ranged from 2225 $MeV$ to 2234 $MeV$.

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arXiv1999

Deltaron Dibaryon Structure in Chiral SU(3) Quark Model

We discuss the structure of Deltaron dibaryon in the chiral SU(3) quark model. The energy of Deltaron is obtained by considering the coupling of the $ΔΔ$ and $CC$ (hidden color) channels. The effects of various parameters on the Deltaron mass are also studied. It is shown that the mass of Deltaron is lower than the mass of $ΔΔ$ but higher than the mass of $ΔN π$.

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arXiv1998

Nonperturbative Corrections to One Gluon Exchange Quark Potentials

The leading nonperturbative QCD corrections to the one gluon exchange quark-quark, quark-antiquark and $q \bar{q}$ pair-excitation potentials are derived by using a covariant form of nonlocal two-quark and two-gluon vacuum expectation values. Our numerical calculation indicates that the correction of quark and gluon condensates to the quark-antiquark potential improves the heavy quarkonium spectra to some degree.

hep-ph↗

arXiv1997

Possible effects of quark and gluon condensates in quarkonium spectra

The Cornell potential with the best fitted parameters $α_{s}$ and $κ$ are modified by adding terms derived from non-perturbative QCD, which are characterized by a series of non-vanishing vacuum condensates of quarks and gluons. In terms of this potential, we study the system of heavy quarkonia. The results show that the correction caused by the additional terms reduces the deviation between the data and the values calculated with the pure Cornell potential and improves the splittings of energy levels. The achievements indicate that the non-perturbative effects induced by vacuum condensates play an important role for the correction to $1/q^2$, which in general was phenomenologically put in by hand. This result would be helpful for understanding non-perturbative QCD along a parallel direction to the QCD sum rules.

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