arXiv subjects

Qi-Fang Lü

Publications and source records attributed to Qi-Fang Lü.

66 records · Page 4Linked to original sources

arXiv2016

Properties of single cluster structure of $d^*(2380)$ in chiral SU(3) quark model

The structure of $d^*(2380)$ is re-studied with the single cluster structure in the chiral SU(3) quark model which has successfully been employed to explain the scattering and binding behaviors of baryonic systems. The mass and width are explicitly calculated with two types of trial wave functions. The result shows that the $(0s)^6 [6]_{orb}$ configuration is easy to convert to the configuration with the same $[6]_{orb}$ symmetry but $2\hbar ω$ excitation back and forth, however, it is seldom to turn into a two-cluster configuration with a (1s) relative motion in between. The resultant mass and width are about $2394$MeV and $25$MeV, respectively, and the stable size is about $0.75fm$, which are consistent with both the results in the two-cluster configuration calculation and the data measured by the COSY collaboration. It seems that the observed $d^*$ is a six-quark dominated exotic state with a spherical shape and breath mode in the coordinate space. Moreover, if $d^*$ does have $2\hbar ω$ excitation, the $d^* \to npπππ$ decay mode might be a good place to distinguish the real structure of the observed phenomenon by COSY. The masses of various isospin-spin states of six-light-quark systems are also computed. It is shown that by considering the coupling with the configurations with $2\hbar ω$ excitations, only the mirror state with $IS$=$30$ will be lower down to the place where whose mass is slightly higher than the value of the $ΔΔ$ threshold.

hep-ph↗

arXiv2016

Strong decay mode $J/ψp$ of hidden charm pentaquark states $P_c^+(4380)$ and $P_c^+(4450)$ in $Σ_c \bar{D}^*$ molecular scenario

We study the strong decay channels $P_c^+(4380) \to J/ψp$ and $P_c^+(4450) \to J/ψp$ under $Σ_c \bar{D}^*$ molecular state ansatz. With various spin-parity assignments, the partial decay widths of $J/ψp$ final state are calculated. Our results show that all the $P$ wave $Σ_c {\bar D}^*$ assignments are excluded, while $S$ wave $Σ_c {\bar D}^*$ pictures for $P_c(4380)$ and $P_c(4450)$ are both allowed by present experimental data. The $J^P=3/2^-$ $Σ_c^* \bar{D}$ and $Σ_c^* \bar{D}^*$ molecules are also discussed in the heavy quark limit, and find that the $Σ_c^* \bar{D}$ system for $P_c(4380)$ is possible. More experimental information on spin-parities and partial decay widths and theoretical investigations on other decay modes are needed to clarify the nature of the two $P_c$ states.

hep-ph↗

arXiv2016

Role of $Y(4630)$ in the $p\bar{p}\rightarrowΛ_c\barΛ_c$ reaction near threshold

We investigate the charmed baryon production reaction $p\bar{p}\rightarrowΛ_c\barΛ_c$ in an effective Lagrangian approach. Besides the $t$-channel $D^0$ and $D^{*0}$ mesons exchanges, the $s$-channel $Y(4630)$ meson exchange is taken into account. For the total cross sections, the $D^0$ and $D^{*0}$ mesons provide minor background contributions, while the $Y(4630)$ state gives a clear peak structure with the magnitude of 10 $μ$b at center of mass energy 4.63 GeV. Basing on the results, we suggest that the reaction of $p\bar{p}\rightarrowΛ_c\barΛ_c$ can be used to search for the $1^{--}$ charmonium-like $Y(4630)$ state, and our predictions can be tested in future by the $\rm{\bar PANDA}$ facility.

hep-ph↗

arXiv2016

Approximate degeneracy of heavy-light mesons with the same $L$

Careful observation of the experimental spectra of heavy-light mesons tells us that heavy-light mesons with the same angular momentum $L$ are almost degenerate. The estimate is given how much this degeneracy is broken in our relativistic potential model, and it is analytically shown that expectation values of a commutator between the lowest order Hamiltonian and ${\vec L}^{~2}$ are of the order of $1/m_Q$ with a heavy quark mass $m_Q$. It turns out that nonrelativistic approximation of heavy quark system has a rotational symmetry and hence degeneracy among states with the same $L$. This feature can be tested by measuring higher orbitally and radially excited heavy-light meson spectra for $D/D_s/B/B_s$ in LHCb and forthcoming BelleII.

hep-ph↗

arXiv2015

Neutral hidden charm pentaquark states $P_c^0(4380)$ and $P_c^0(4450)$ in $π^-p \to J/ψn$ reaction

We investigate the neutral hidden charm pentaquark states $P_c^0(4380)$ and $P_c^0(4450)$ in $π^-p \to J/ψn$ reaction within an effective Lagrangian approach. The background contributions for the process mainly come from $t$-channel $π$ and $ρ$ meson exchanges. The contributions of $P_c^0(4380)$ and $P_c^0(4450)$ states give clear peak structures in the magnitude of 1 $μ$b at center of mass energy 4.38 GeV and 4.45 GeV in the total cross sections. Hence, this reaction may provide a new good platform to search for neutral $P_c$ states. It is expected that our estimated total cross sections together with the angular distributions can be tested by future experiments at J-PARC.

hep-ph↗

arXiv2015

Role of $Λ(1670)$ in the $γp \to K^+ ηΛ$ reaction near threshold

The role of the $Λ(1670)$ resonance in the $γp \to K^+ ηΛ$ reaction near threshold is studied within an effective Lagrangian approach. We perform a calculation for the total and differential cross section of the $γp \to K^+ ηΛ$ reaction by including the contributions from the $Λ(1670)$ intermediate state decaying into $ηΛ$ dominated by $K^-$ and $K^{*-}$ mesons exchanges, the nucleon pole and $N^*(1535)$ resonance decaying into $K^+ Λ$ dominated by exchanges of $ω$ and $K^-$ mesons. Besides, the non-resonance process and contact terms to keep the total scattering amplitude gauge invariant are also considered. With our model parameters, the total cross section of this reaction is of the order of $1$ nanobarn at photon beam energy $E_γ \sim 2.5$ GeV. It is expected that our model predictions could be tested by future experiments.

nucl-th↗

arXiv2015

Nucleon resonances in the $π^- p \to K^0 Λ$ reaction near threshold

We investigate the two-body reaction $π^- p \to K^{0} Λ$ within the effective Lagrangian approach and the isobar model. In addition to the "background" contributions from $t$-channel $K^*$ exchange, $u$-channel $Σ(1192)$ and $Σ^*(1385)$ exchanges, and $s$-channel nucleon pole terms, the contributions from the nucleon resonances $N^*(1535)$, $N^*(1650)$, and $N^*(1720)$ are investigated. It is shown that the inclusion of these nucleon resonances contributions leads to a good description of the experimental total and differential cross sections data at low energy region. The $s$-channel $N^*(1535)$, $N^*(1650)$, and $N^*(1720)$ resonances and the $t$-channel $K^*$ exchange give the dominant contributions below $W = 1.76$ GeV, while the $u$-channel $Σ(1192)$ and $Σ^*(1385)$ exchanges give the minor contributions.

nucl-th↗

arXiv2015

Nucleon resonances in the $γp \to ϕK^+ Λ$ reaction near threshold

We investigate the $γp \to ϕK^+ Λ$ reaction near threshold within an effective Lagrangian approach and the isobar model. Various nucleon resonances caused by the $π$ and $η$ meson exchanges and background contributions are considered. It is shown that the contribution from the $N^*(1535)$ resonance caused by the $η$ meson exchange plays the predominant role. Hence, this reaction provides a good new platform to study the $N^*(1535)$ resonance. The predicted total cross section and specific features of angular distributions can be tested by future experiments.

nucl-th↗

arXiv2015

Near-threshold $η$ production in $pp$ collisions

We study near-threshold $η$ meson production in $pp$ collisions within an effective Lagrangian approach combined with the isobar model, by allowing for the various intermediate nucleon resonances due to the $π$, $η$, and $ρ$-meson exchanges. It is shown that the $ρ$-meson exchange is the dominant excitation mechanism for these resonances, and the contribution from the $N^*(1720)$ is dominant. The total cross section data can be reasonably reproduced, and the anisotropic angular distributions of the emitted $η$ meson are consistent with experimental measurements. Besides, the invariant mass spectra of $pp$ and $pη$ explain the data well at excess energy of 15 MeV, and are basically consistent with the data at excess energy of 40 MeV. However, our model calculations cannot reasonably account for the two-peak structure in the $pη$ distribution at excess energies of 57 and 72 MeV, which suggests that a more complicated mechanism is needed at higher energy region.

nucl-th↗

arXiv2014

Nucleon pole contribution in the $pp\to ppK^+K^-$ reaction below the $ϕ$ meson threshold

Nucleon pole contribution in the $pp\to ppK^+K^-$ reaction below the threshold of the production of the $ϕ$ meson is studied within the effective Lagrangian approach. It is assumed that the $K^- p$ final state originates from the decay of the hyperons $Λ(1115)$ and $Λ(1405)$. In addition to the $pp$ final state interaction (FSI) parametrized using the Jost function, we have also considered the $K^+K^-$ FSI with the techniques of the chiral unitary approach, where the scalar mesons $f_0(980)$ and $a_0(980)$ were dynamically generated. Hence, the contributions from scalar mesons $f_0(980)$ and $a_0(980)$ occur through the $K^+ K^-$ FSI. It is shown that the available experimental data are well reproduced, especially the total cross sections and the invariant mass distributions of $pp$ and $K^+K^-$. Furthermore, different forms of the couplings (pseudoscalar and pseudovector) for the $πNN$ interaction and different strengths for the proton-proton FSI are also investigated. It is found that the contributions from hyperon $Λ(1115)$ and $Λ(1405)$ are different between these two kinds of couplings. On the other hand, the effects of the proton-proton FSI can be adjusted by the cut off parameters used in the form factors.

hep-ph↗

arXiv2014

Understanding the charmed states recently observed by the LHCb and BaBar Collaborations in the quark model

Comparing the expected spectroscopy in the relativistic quark model and the predicted strong decays in the $^3P_0$ model employing the realistic wave functions from the relativistic quark model with the measured properties of the LHCb and BaBar charmed states, we find that the masses and strong decays of these charmed states can be reasonably explained in the conventional $q\bar{q}$ picture, and therefore suggest that the $D(2550)$/$D_J(2580)$, $D^*(2600)$/$D^*_J(2650)$, $D(2750)$/$D_J(2740)$, $D^*(2760)$/$D^*_J(2760)$, $D_J(3000)$, and $D^*_J(3000)$ can be identified as the $D(2^1S_0)$, $D(2^3S_1)$, $D^\prime_2(1D)$, $D(1^3D_3)$, $D(3^1S_0)$, and $D(1^3F_4)$, respectively.

hep-ph↗

arXiv2013

The near threshold $π^- p \to ηn$ reaction in an effective Lagrangian approach

The near threshold $π^- p \to ηn$ reaction is studied within an effective Lagrangian approach and the isobar model. By considering the contributions from $s$- and $u$-channel nucleon pole and $N^{*}(1535)$ resonance, the total and differential cross sections of the $π^- p \to ηn$ reaction near threshold are calculated. Our theoretical results can fairly reproduce the current experimental data. It is also shown that while the center-of-mass energy lies in the range from the reaction threshold up to $1.65$ GeV, $s$-channel $N^{*}(1535)$ resonance plays the dominant role. The effect from nucleon pole is found to be small but the interference terms between the $N^*(1535)$ resonance and the nucleon pole are significant. The contributions from $t$-channel processes are negligible in the present calculation.

hep-ph↗