arXiv subjects

Xuan-Heng Zhang

Publications and source records attributed to Xuan-Heng Zhang.

7 recordsLinked to original sources

arXiv2026

Exclusive Leptonium Electroproduction

Purely leptonic bound states provide precision probes of QED. Positronium $(e^+e^-)$ and muonium $(μ^+e^-)$ have long been observed, whereas dimuonium $(μ^+μ^-)$ and tauonium $(τ^+τ^-)$ remain undiscovered. We study exclusive vector-leptonium electroproduction in $ep$ collisions within nonrelativistic QED. We include the Bethe--Heitler and double deeply virtual Compton scattering contributions and their interference, and calculate the NLO QCD hard-scattering kernels entering the dominant Compton form factor $\Hcal$ within collinear GPD factorization. The NLO QCD correction to the DDVCS contribution changes from a strong suppression at low photon virtuality to a sizable enhancement as the lower virtuality cut is raised, with the gluon channel providing the dominant contribution. Bethe--Heitler production dominates the exclusive rate, supporting dedicated dimuonium searches at the EIC and JLab, with larger samples expected at higher-energy electron--proton colliders. The much larger positronium samples provide a high-statistics environment for precision QED studies, whereas tauonium production remains strongly suppressed.

hep-ph↗

arXiv2026

Mass Spectra of $Λ_Q\barΣ_Q$ Hexaquark States in QCD Sum Rules

Recently, the BESIII Collaboration indicate that no $Λ_c\barΣ_c$ bound-state with a mass near threshold in the range $4715$--$4735~\mathrm{MeV}$ was observed. In order to determine the plausible mass region of the states in this structure, we calculate the mass spectrum of the $Λ_c\barΣ_c$ configuration with the method of QCD sum rules. Two linearly independent interpolating currents are constructed, and contributions from nonperturbative condensates up to dimension 12 are included in the numerical results. Consequently, we obtain the masses of the candidate states with quantum numbers $J^P = 0^-,\,0^+,\,1^-,\,1^+$. Our results show that the central values of the $Λ_c\barΣ_c$ ground-state masses lie around the $5.8~\mathrm{GeV}$ region, which do not support them as bound states and consistent with the findings reported by the BESIII Collaboration. Furthermore, we compute the mass spectrum of the $Λ_b\barΣ_b$ states with quantum numbers $J^P = 0^-,\,0^+,\,1^-,\,1^+$, which could be served as hidden-bottom candidates in the experimental detecting.

hep-ph↗

arXiv2026

Spectrum of Light Hexaquark States in Triquark-antitriquark Configuration

To understand the nature of $X(2075)$ and $X(2085)$ observed by the BESIII collaboration in the $p\barΛ$ system, we systematically investigate the possibility that these states are compact hexaquark with triquark-antitriquark configurations for the first time. Within the framework of QCD sum rules, the mass spectrum and decay constants of such hexaquark states with quantum numbers $J^P=0^-, 0^+, 1^-, 1^+$ are studied. Consequently, six independent and nondegenerate hexaquark candidates are obtained, among which two $J^P = 1^-$ states exhibit masses consistent with $X(2075)$, while the two $J^P = 1^+$ states differ markedly from the mass of $X(2075)$ or $X(2085)$. The remaining two states with $J^P = 0^+$ and $0^-$ may serve as predictions for potential compact hexaquark configurations. Furthermore, the possible decay modes of these hexaquark states are analyzed, which could be the experimental signatures for their identification.

hep-ph↗

arXiv2026

The Spectra of $p\barΛ$ and $p\barΣ$ Hexaquark States

Motivated by the observation of the $J^P = 1^+$ resonance $X(2085)$ in the $p\barΛ$ system by the BESIII collaboration, we studied the molecular states of hexaquarks $p\barΛ$ and $p\barΣ$ with baryon-antibaryon structures within the framework of the QCD sum rules. Non-perturbative contributions up to dimension 13 were considered in our analysis. The results indicate the existence of six possible molecular states $p\barΛ$ and $p\barΣ$, with quantum numbers $J^{P}=0^{-}, 0^{+}, 1^{-}$. Consequently, the current sum rule results do not support the interpretation of $X(2085)$ as a $p\barΛ$ or $p\barΣ$ molecular state. On the other hand, we find that the masses of the proposed $p\barΛ$ and $p\barΣ$ structures with $J^{P} = 1^{-}$ are in the vicinity of observed $X(2075)$, which implies that the nature of this state needs more invistigations. Moreover, the possible decay modes of the concerned hexaquark states are analyzed.

hep-ph↗

arXiv2025

NLO Corrections to Dimuonium Production in Photon-Photon Collision

Dimuonium ($μ^+ μ^-$) is one of the pure QED bound systems of leptons, together with positronium and ditauonium. The former had been observed in experiment in 1951, while the search for dimuonium and ditauonium ($τ^+ τ^-$) are still in vain. The ditauonium is thought to be hard to measure due to its short life time, whereas the dimuonium is very likely to be observed in current running experiments. We calculate in this work the para and ortho dimuonium production in photon-photon collision at the next-to-leading order (NLO) in QED. To handle the Coulomb divergence within the bound system, the non-relativistic QED description is adopted for consistency. The results indicate that the NLO corrections are negative for both para and ortho states, at the normal order of perturbative QED corrections. The measurement of the dimuonium in Belle II experiment, especially at the forthcoming facility of STCF, is tenable.

hep-ph↗

arXiv2024

Hyperon semileptonic decays in QCD sum rules

We investigate the hyperon semileptonic decays within the framework of QCD sum rules. The flavor $ SU(3) $ symmetry breaking effects are analyzed via the relevant form factors and corresponding branching fractions. Employing the $ z $-series parameterization to capture the $ q^2 $ dependence of form factors, we calculate the hyperon semileptonic decay rates and confront them with the recent experimental measurements. Moreover, we calculate as well the non-standard tensor form factors, which involve certain new physics beyond the standard model.

hep-ph↗

arXiv2021

Higher-twist corrections to $D\toπ,K$ form factors from light-cone sum rules

We calculate the $D\to P$ transition form factors within the framework of the light-cone QCD sum rules (LCSR) with the $D$-meson light-cone distribution amplitudes (LCDAs). The next-to-leading power (NLP) corrections to the vacuum-to-$D$-meson correlation function are considered, and the NLP corrections from the high-twist $D$-meson LCDAs and the SU(3) breaking effect from strange quark mass are investigated. Adopting the exponential model of the $D$-meson LCDAs,the predicted SU(3) flavor symmetry breaking effects are $R_{SU(3)}^{+,0}=1.12$ and $R_{SU(3)}^{T}=1.39$, respectively, which confirms the results from LCSR with pion LCDA. The numerical predictions of the form factors show that the contribution from two-particle higher-twist contributions is of great importance and the uncertainties are dominated by the inverse moment of $ϕ_D^+(ω, μ)$. With the obtained form factors, the predicted Cabibbo-Kobayashi-Maskawa (CKM) matrix elements are $|V_{cd}|=0.151\,{}^{+0.091}_{-0.043} \big |_{\rm th.}\,{}^{+0.017}_{-0.02} \big |_{\rm exp.}$ and $|V_{cs}|=0.89\,{}^{+0.467}_{-0.234} \big |_{\rm th.}\,{}^{+0.008}_{-0.008} \big |_{\rm exp.}$.

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