arXiv subjects

Zi-Xuan Ma

Publications and source records attributed to Zi-Xuan Ma.

4 recordsLinked to original sources

arXiv2026

$Ξ_c(3055)$ as a scaling point to establish the excited $Ξ_c^{(\prime)}$ family

The low-lying orbital excitations of $Ξ_c^{(\prime)}$ baryons are studied within the chiral quark model combined with the $^3P_0$ decay mechanism. Motivated by the LHCb observation that $Ξ_c(3055)$ is a $λ$-mode $1D$ state with $J^P=3/2^+$, we take it as a reference to constrain model parameters and perform a systematic analysis of states below 3.1 GeV. Our results provide a consistent interpretation of the observed $Ξ_c$ spectrum: $Ξ_c(2790)$ and $Ξ_c(2815)$ are well described as a $λ$-mode $1P$ doublet, the structures around 2.9 GeV can be interpreted as $P$-wave excitations with mixed $λ/ρ$ modes, and $Ξ_c(2970)$ is consistent with a $2S$ assignment. Furthermore, $Ξ_c(3055)$ together with $Ξ_c(3080)$ forms a $λ$-mode $D$-wave doublet, while $Ξ_c(3123)$ favors a $1D$ assignment. These results provide a coherent picture of the low-lying $Ξ_c$ spectrum and call for further experimental tests.

hep-ph↗

arXiv2025

Proper constituent gluon mass as the final piece to construct hybrid mesons

In this letter, we propose that a proper constituent gluon mass $m_g$=450 MeV can be applied to identify the hybrids composed of quarks and gluons. By investigating the spectra and decay widths of the light hybrids $(q\bar{q}g)$ with $J^P=1^{-+}$, we find the $π_1(1600)$ and $η_1(1855)$ may not be explained as $1^{-+}$ hybrids, simultaneously, and the $η_1(1855)$ observed by BESIII may not be a hybrid. In addition, we predict an existence of a hybrid $η_1(1640)$, which can be verified by searching the $a_1(1260)π$ channel. Moreover, we suggest the $K_1(1270)\bar{K}$ and $K_1(1270)π$ as the golden channels to search for an isospin-0 and an isospin-$\frac{1}{2}$ hybrids, respectively.

hep-ph↗

arXiv2025

Investigating the nature of $N(1535)$ and $Λ(1405)$ in a quenched chiral quark model

In this work, we systematically study $N(1440)$, $N(1535)$, and $Λ(1405)$ in both the quenched three-quark and five-quark frameworks using the Gaussian Expansion Method (GEM) within the chiral quark model. Our calculations show that $N(1535)$ can be reproduced as a three-quark state ($N(1P)$), while $N(1440)$ and $Λ(1405)$ cannot be accommodated as the three-quark candidates, ($N(2S)$ and $Λ(1P)$), respectively. In the five-quark framework, we find that the $ΛK$ state for $N(1535)$ can not form a bound state, while in the $N\bar{K}$ channel there will $Λ(1405)$ form a shallow bound state. Based on the complex-scaling method, we performed complete coupled-channels calculations and obtained six resonance states with energies ranging from 1.8 GeV to 2.2 GeV, in addition with one bound state located around $Σπ$ channel. However, neither molecular candidates in $ΛK$ channel for $N(1535)$ nor $N\bar{K}$ for $Λ(1405)$ are included in these states. This is because the strong coupling between $N\bar{K}$ and $Σπ$ will make the $N\bar{K}$ unbound, while the weak coupling between $ΛK$ and $ΣK$ can not help form a stable structure around $ΛK$ threshold. Thus, under the quenched quark model, our results support $N(1535)$ as a three-quark state, while $N(1440)$ is neither a three-quark nor a five-quark state. In addition, we find that although $Λ(1405)$ can be primarily a five-quark state, it requires a mixture of three-quark and five-quark components for stability. In the future, an exploration on the mixing effects between bare baryons with these relevant two-body hadronic channel components will be carried out to further test our conclusions.

hep-ph↗

arXiv2024

The role of triangle singularity in isospin breaking process $J/ψ\to Λ\barΛ π$ and the possible evidence of $Σ^*(\frac{1}{2}^-)$ states

In this study, the impact of triangle singularity is investigated in the isospin-breaking process $J/ψ\to Λ\barΛ π$. The triangle singularity is found to play a significant role in the process, resulting in the creation of a resonance-like structure around 1.4 GeV in the $Λπ(\barΛπ)$ invariant mass spectrum. To amplify the impact of this triangle singularity, the presence of two $Σ^*(\frac{1}{2}^-)$ states around 1.4 GeV and 1.6 GeV is essential, yet these states have not been definitively identified in the current baryon spectrum. We recommend that experiments, particularly the Beijing Spectrometer (BESIII) and the future Super Tau-Charm Factory (STCF), to investigate the process $J/ψ\to Λ\barΛ π$ to offer direct evidences for our predicted triangle singularity and additional evidence regarding the $Σ(\frac{1}{2}^-)$ states.

hep-ph↗