arXiv subjects

Zejian Zhuang

Publications and source records attributed to Zejian Zhuang.

4 recordsLinked to original sources

arXiv2026

Machine learning unveils the quark mass dependence of the pseudoscalar meson decay constants in three-flavour N$^2$LO ChPT

The quark mass dependence of the pseudoscalar meson decay consntants, $f_π, f_K$ and $f_η$, are determined from three-flavor N$^2$LO ChPT till pion masses around $780$ MeV, near the SU(3) limit. This is done by conducting an analysis of recent LQCD data using the LASSO method, a machine-learning technique which allows to pin down the relevant low-energy-constants with high precision. Since the pion decay constant is a fundamental quantity which usually appears in relevant phenomenological lagrangians or Effective Field Theories based on QCD at low energies, this analysis can be used as input to evaluate the quark mass dependence of hadronic states. As an example, we predict the masses of the octect baryons in the SU(3) limit within covariant Baryon Chiral Perturbation Theory.

hep-ph↗

arXiv2026

Revealing the $D_0^*(2300)$ two-pole structure from lattice data and the SU(3) limit

We perform an analysis of LQCD light - charmed (pseudoscalar) meson scattering data with UChPT for pion masses ranging from $m_π\simeq 230$~MeV till the SU(3) limit, $m_π\simeq 700$~MeV. We find two poles in the non-strange isospin $I=1/2$ sector that can be related to the experimental $D_0(2300)$ resonance. At the physical pion mass, the poles are located at $\sqrt{s_0}=2094(7)(1)-i111(7)(13)$ MeV, and $2463(60)(30)-i108(14)(12)$~MeV. While the first pole, named here $D_0^*(2100)$, is always a resonance in $Dπ$ within the $1σ$ region, the second pole can be a resonance or virtual state close to the $Dη, D_s\bar{K}$ thresholds. For the first time, the pion mass dependence on different chiral trajectories including SU(3) LQCD data are investigated for these poles. We find that in the $m_s=m_{s,\mathrm{phy}}$ trajectory, the $D_0^*(2100)$ resonance pole behaves similarly as the $σ$ resonance in $ππ$ scattering, splitting into two poles, connected to the $\bar{\mathbf{3}}$ representation. Moreover, we found that the higher pole related to the experimental $D_0^*(2300)$ can be related to the $\mathbf{6}$ representation. We highlight that since this pole couples strongly to channels with hidden strangeness, its mass is fairly constant in the $\mathrm{Tr}[M]=C$ trajectory, what can be tested in future LQCD simulations. The compositeness of the $D_0^*(2100)$ state at the SU(3) limit is evaluated. Finally, other sectors are also discussed.

hep-ph↗

arXiv2025

Pole trajectories of the $Λ(1405)$ helps establish its dynamical nature

The $Λ(1405)$ has been one of the most controversial exotic baryons. If the $Λ(1405)$ possesses a two-pole molecular structure, these poles are expected to evolve differently towards the SU(3) limit. From an analysis of a recent LQCD simulation on the $πΣ-\bar{K}N$ scattering for $I=0$ and the study of the quark mass dependence of the octet baryon masses, we determine for the first time the trajectories of these poles towards the symmetric point over the $\mathrm{Tr}[M]=C$ trajectory accurately. At $m_π\simeq 200$ MeV, our results are consistent with the lattice simulations, and the extrapolations to the physical point, based on the NLO chiral Lagrangians, agree well with existing experimental analyses. We predict qualitatively similar trajectories at LO and up to NLO, consistent with the LO interaction's dominance. At the SU(3) symmetric point of this trajectory, both poles are on the physical sheet, and the lower pole is located at $E^{(1)}=1573(6)(6)$ MeV, becoming a SU(3) singlet, while the higher pole at $E^{(8a)}=1589(7)(5)$ MeV couples to the octet representation. Moreover, we make predictions in $I=1$ for the $Σ^*$ resonance. We find a resonance pole that evolves into a bound state around $m_π=415$ MeV in this sector. The results presented here are crucial to shed light on the molecular nature of exotic strange baryon resonances and can be tested in future LQCD simulations.

hep-ph↗

arXiv2022

The lineshape of the compact fully heavy tetraquark

Hadrons and their distributions are the most direct observables in experiment, which would shed light on the non-perturbative mystery of quantum chromodynamics (QCD). As the result, any new hadron will challenge our current knowlege on the one hand, and provide additional inputs on the other hand. The fully heavy $cc\bar{c}\bar{c}$ system observed by LHCb recently opens a new era for hadron physics. We first extract the internal structure of the fully heavy tetraquarks directly from the experimental data, within the compact tetraquark picture. By fitting to the di-$J/ψ$ lineshape, we find that the $X(6900)$ is only cusp effect from the $J/ψψ(3770)$ channel. In addition, there is also a cusp slightly below $6.8~\mathrm{GeV}$ stemming from the $J/ψψ^\prime$ channel. The two $0^{++}$ tetraquarks behave as two resonances above the di-$η_c$ and di-$J/ψ$ threshold, respectively. The $2^{++}$ state is a bound state below the di-$J/ψ$ threshold. Furthermore, we find that the $X_{0^{++}}(6035)$ shows a significant structure in the di-$η_c$ lineshape even after the coupled channel effect. This is an unique feature which can distinguish compact $cc\bar{c}\bar{c}$ tetraquark from the loosely hadronic molecules.

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