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Peng-Nian Shen

Publications and source records attributed to Peng-Nian Shen.

34 records · Page 2Linked to original sources
arXiv2006

Study on Strong Decays of $D_{sJ}(2632)$

The resonance $D_{sJ}(2632)$ observed by SELEX, has attracted great interests and meanwhile brought up serious dispute. Its spin-parity, so far has not finally determined and if it exists, its quark-structure might be exotic. Following the previous literature where $D_{sJ}(2632)$ is assumed to be a radial-excited state of $1^-$, we consider the possibilities that it might be a $q\bar q$ ground state of $2^+$ or the first radial-excited state of $0^+$ $D_{sJ}(2317)$ and re-calculate its strong decay widths in terms of the Bethe-Salpeter equation. Our results indicate that there still is a sharp discrepancy between the theoretical evaluation and data.

hep-ph↗
arXiv2006

Spectra of Free Diquark in the Bethe-Salpeter Approach

In this work, we employ the Bethe-Salpeter (B-S) equation to investigate the spectra of free diquarks and their B-S wave functions. We find that the B-S approach can be consistently applied to study the diqaurks with two heavy quarks or one heavy and one light quarks, but for two light-quark systems, the results are not reliable. There are a few free parameters in the whole scenario which can only be fixed phenomenologically. Thus, to determine them, one has to study baryons which are composed of quarks and diquarks.

hep-ph↗
arXiv2005

Contributions from Goldstone-boson-exchange to baryon spectra in the MIT Bag Model

We discuss contributions of chiral bosons to baryon spectra in the MIT bag model. It is believed that within hadrons, chiral bosons are degrees of freedom which are independent of gluons to provide strong interactions between quarks. In the original MIT bag model, only interaction mediated by gluon exchanges was considered, by contrast, in this work we take into account the interaction mediated by the exchanges of chiral bosons $σ$ and $π^{(\pm,0)}$. Then following the standard approach, we minimize the effective hamiltonian which includes both the contributions from gluon and chiral-boson exchanges with respect to the bag radius to obtain the effective radius. By re-fitting the spectra of baryons, we find that the contributions from the boson-exchange may be 40% of that from gluon-exchanges and meanwhile the bag constant $B$, the zero-point energy $z_0$ almost do not change. It indicates that in the original version of the MIT bag model, the intermediate-distance interaction due to the chiral-boson exchanges is attributed into the effective coupling $α_c$ which stood for the short-distance interaction caused by the gluon exchanges and the long-distance effects reflected by $B$ and $z_0$ are not influenced.

hep-ph↗
arXiv2004

Sum rules on quantum hadrodynamics

The development on relativistic nuclear many-body theories is reviewed. The second order self-energies of hadrons are calculated from $\hat{S}_2$ matrix, and then an effective method to solve nuclear many-body problems, sum rules on quantum hadrodynamics, is summarized. The differences between this method and quantum hadrodynamics are discussed. The effective nucleon mass in the nuclear matter is redefined in the relativistic Hartree approximation, and a self-consistent relativistic mean-field model based on quantum hadrodynamics 2 is proposed. It is pointed out that the original definition on effective nucleon mass in quantum hadrodynamics 2 is not self-consistent, and all the parameters in the relativistic mean-field approximation should be fixed again according to the new definition.

nucl-th↗
arXiv2004

Can the observed enhancement in the mass spectrum of p \bar p in J/ψ\to γp \bar p be interpreted by a possible p \bar p bound state

Provided the enhancement in the $p \bar{p}$ spectrum in radiative decay $J/ψ\to γp \bar{p}$ observed by the BES collaboration is due to an existence of a $p \bar{p}$ molecular state, we calculate its binding energy and lifetime in the linear $σ$ model. We consider a possibility that the enhancement is due to a $p \bar p$ resonance which is in either S-wave or P-wave structure and compare our results with the data.

hep-ph↗
arXiv2004

Nuclear effects in polarized proton-deuteron Drell-Yan processes

The longitudinally polarized Drell-Yan process is one of most powerful tools to probe the structure of hadrons. By means of the recent formalism of the polarized proton-deuteron(pd) Drell-Yan, we calculate the ratio of the proton-deuteron Drell-Yan cross section to the proton-proton(pp) one $Δσ_{pd}/2Δσ_{pp}$in the polarized case.The theoretical results can be compared with future experimental data to confirm the nuclear effect due to the six-quark cluster in deuteron .

hep-ph↗
arXiv2004

Evaluation of Spectra of Baryons Containing Two Heavy Quarks in Bag Model

In this work, we evaluate the energy spectra of baryons which consist of two heavy and one light quarks in the MIT bag model. The two heavy quarks constitute a heavy scalar or axial vector diquark. Concretely, we calculate the spectra of $|q(QQ')>_{1/2}$ and $|q(QQ')>_{3/2}$ where $Q$ and $Q'$ stand for $b$ and/or $c$ quarks. Especially, for $|q(bc)>_{1/2}$ there can be a mixing between $|q(bc)_0>_{1/2}$ and $|q(bc)_1>_{1/2}$ where the subscripts 0 and 1 refer to the spin state of the diquark (bc), the mixing is not calculable in the framework of quantum mechanics (QM) as the potential model is employed, but can be evaluated by the quantum field theory (QFT). Our numerical results indicate that the mixing is sizeable

hep-ph↗
arXiv2004

Nucleon pole contributions in $J/ψ\to N \bar{N} π$, $p \bar{p} η$, $p \bar{p} η^{\prime}$ and $p \bar{p} ω$ decays

Nucleon pole contributions in $J/ψ\to N \bar N π$, $p \bar p η$, $p \bar p η^{\prime}$ and $p \bar{p} ω$ decays are re-studied. Different contributions due to PS-PS and PS-PV couplings in the $π$-N interaction and the effects of $NNπ$ form factors are investigated in the $J/ψ\to N \bar N π$ decay channel. It is found that when the ratio of $|F_0| /|F_M|$ takes small value, without considering the $NNπ$ form factor, the difference between PS-PS and PS-PV couplings are negligible. However, when the $NNπ$ 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 $J/ψ\to N\bar{N}π$ decay and must be accounted. In the $J/ψ\to N\bar{N}η$ and $N\bar{N}η'$ decays, its contribution is less than 0.1% of the data. In the $J/ψ\to N\bar{N}ω$ 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.

nucl-th↗
arXiv2004

Estimating Mass of Sigma-Meson and Study on Application of the Linear Sigma-Model

Whether the $σ-meson$ ($f_0(600)$) exists as a real particle is a long-standing problem in both particle physics and nuclear physics. In this work, we analyze the deuteron binding energy in the linear $σ$ model and by fitting the data, we are able to determine the range of $m_σ$ and also investigate applicability of the linear $σ$ model for the interaction between hadrons in the energy region of MeV's. Our result shows that the best fit to the data of the deuteron binding energy and other experimental data about deuteron advocates a narrow range for the $σ-$meson mass as $520\leq m_σ\leq 580$ MeV and the concrete values depend on the input parameters such as the couplings. Inversely fitting the experimental data, our results set constraints on the couplings. The other relevant phenomenological parameters in the model are simultaneously obtained.

hep-ph↗
arXiv2002

Effective photon mass in nuclear matter and finite nuclei

Electromagnetic field in nuclear matter and nuclei are studied. In the nuclear matter, because the expectation value of the electric charge density operator is not zero, different in vacuum, the U(1) local gauge symmetry of electric charge is spontaneously broken, and consequently, the photon gains an effective mass through the Higgs mechanism. An alternative way to study the effective mass of photon is to calculate the self-energy of photon perturbatively. It shows that the effective mass of photon is about $5.42MeV$ in the symmetric nuclear matter at the saturation density $ρ_0 = 0.16fm^{-3}$ and about $2.0MeV$ at the surface of ${}^{238}U$. It seems that the two-body decay of a massive photon causes the sharp lines of electron-positron pairs in the low energy heavy ion collision experiments of ${}^{238}U+{}^{232}Th$ .

nucl-th↗
arXiv2002

Relativistic mean-field approximation with density-dependent screening meson masses in nuclear matter

The Debye screening masses of the $σ$, $ω$ and neutral $ρ$ mesons and the photon are calculated in the relativistic mean-field approximation. As the density of the nucleon increases, all the screening masses of mesons increase. It shows a different result with Brown-Rho scaling, which implies a reduction in the mass of all the mesons in the nuclear matter except the pion. Replacing the masses of the mesons with their corresponding screening masses in Walecka-1 model, five saturation properties of the nuclear matter are fixed reasonably, and then a density-dependent relativistic mean-field model is proposed without introducing the non-linear self-coupling terms of mesons.

nucl-th↗
arXiv1999

Application of Hypervirial Theorem As Criteria For Accuracy of Variational Trial Wave Function

It would be interesting to investigate the accuracy of the results obtained in the variational method, because it is important for studying hadron spectra. One can define some criteria to judge the accuracy, or the quality of the trial function. We employ a simple potential form to check how accurate the variational results obtained by a single-parameter trial function can be. All the concerned problems, in particular, the relevant aspects on the application of hypervirial theorem in variational method for various potential forms, are discussed in every detail. The qualitative conclusion of the work can be generalized to much more complicated cases. Our study suggests that the hypervirial relations can serve as a good and practical criterion for judging the accuracy of any trial functions.

hep-ph↗
arXiv1999

Spectra of Baryons Containing Two Heavy Quarks in Potential Model

In this work, we employ the effective vertices for interaction between diquarks (scalar or axial-vector) and gluon where the form factors are derived in terms of the B-S equation, to obtain the potential for baryons including a light quark and a heavy diquark. The concerned phenomenological parameters are obtained by fitting data of $B^{(*)}-$mesons instead of the heavy quarkonia. The operator ordering problem in quantum mechanics is discussed. Our numerical results indicate that the mass splitting between $B_{3/2}(V), B_{1/2}(V)$ and $B_{1/2}(S)$ is very small and it is consistent with the heavy quark effective theory (HQET).

hep-ph↗
arXiv1999

Singularity in Potential, Perturbation and Variational Methods

In this work, we carefully study the energy eigen-values and splitting of heavy quarkonia as there exist $1/r^3$ and $δ^3(\vec r)$ singular terms in the potential which make a direct numerical solution of the Schrödinger equation impossible. We compare the results obtained in terms of perturbation and variational methods with various treatments.

hep-ph↗
arXiv1998

Variational Estimation of the Wave Function at Origin for Heavy Quarkonium

The wave function at the origin (WFO) is an important quantity in studying many physical problems concerning heavy quarkonia. However, when one used the variational method with fewer parameters, in general, the deviation of resultant WFO from the "accurate" solution was not well estimated. In this paper, we discuss this issue by employing several potential forms and trial wave functions in detail and study the relation between WFO and the reduced mass.

hep-ph↗