arXiv subjects

Ling-Yun Dai

Publications and source records attributed to Ling-Yun Dai.

At least 19 recordsLinked to original sources

arXiv2026

Precision Sum Rule for Nucleon Isovector Polarizabilities and the Proton-Neutron Mass Difference

The precision of the electromagnetic proton-neutron mass difference $δm_\mathrm{QED}$ extracted from the Cottingham formula hinges on a subtraction function whose low-energy normalization $\bar S(0)$ is fixed by the isovector combination of the proton and neutron polarizabilities, $(α_{E1}-β_{M1})^{p-n}$. We derive a dispersive sum rule for this combination in terms of $s$-channel photoabsorption cross sections and the product of $t$-channel $γγ\toπη/K\bar K_{I_t=1}$ and $πη/K\bar K_{I_t=1}\to N\bar N$ amplitudes, without invoking Reggeon dominance. Combining empirical pion-photoproduction multipoles with coupled-channel Muskhelishvili--Omnès representations of the scalar-isovector $πη/K\bar K$ amplitudes, we obtain $(α_{E1}-β_{M1})^{p-n}=-2.26(73)\times10^{-4}\,\mathrm{fm}^3$, fixing its sign and reducing the uncertainty by a factor of 4 compared with the previously known value. This result yields $\bar S(0)=-1.76(61)\,\mathrm{GeV}^{-2}$, leading to $δm_\mathrm{QED}=0.71^{+0.03}_{-0.06}\,\mathrm{MeV}$, substantially more precise than previous Cottingham determinations. The negative $\bar S(0)$ also provides a stringent low-energy test of Reggeon dominance in the subtraction function.

hep-ph↗

arXiv2026

Study of electron-positron annihilation into four pions within chiral effective field theory in the low energy region

In this paper, we employ chiral effective field theory to study the process of electron-positron annihilation into four pions in the low energy region within $E_{c.m.}\leq 0.6$ GeV. The prediction of the cross section is obtained through $SU(3)$ chiral perturbation theory up to the next-to-leading order, which is smaller than the experimental data in the energy region [0.6-0.65] GeV, though the data has only a few points and poor statistics. Then, the resonance chiral theory is applied to include the resonance contribution, with the lightest scalars and vectors written in the effective Lagrangians. A series of relevant decay widths and the masses of the vectors are studied to fix the unknown couplings. The resonance contribution should be one order larger than that of the chiral perturbation theory but still one to two orders smaller than the data. The significant discrepancy urged the new experimental measurements to give more guidance. We also compute the leading order hadronic vacuum polarization contribution from the four pion channels to the anomalous magnetic moment of the muon, $(g-2)_μ$. In the energy range from threshold up to 0.6 GeV within resonance chiral theory, the contributions are $a_μ=(0.680\pm0.062)\times10^{-16}$ and $a_μ=(0.597\pm0.058)\times10^{-16}$ for the processes of $e^+e^-\toπ^+π^+π^-π^-$, $π^0π^0π^+π^-$, respectively.

hep-ph↗

arXiv2026

Hadronic Contributions to the Muon $g-2$ in Improved Holographic QCD Models

We present a systematic study of the hadronic contributions to the muon anomalous magnetic moment within several infrared-improved AdS/QCD models. The models are constrained by the pion decay constant and the $ρ$-meson mass and are shown to reproduce phenomenologically reasonable low-energy hadron spectra. Within a unified holographic framework, we evaluate both the leading-order hadronic vacuum polarization contribution and the pseudoscalar-pole contribution to hadronic light-by-light scattering. The holographic predictions for the hadronic vacuum polarization contribution are found to be systematically lower than recent dispersive determinations, and we demonstrate that this discrepancy is closely correlated with an underestimation of the $ρ$-meson decay constant in the models. We further compute the pion transition form factor and the corresponding pseudoscalar-pole hadronic light-by-light contribution. Although the models yield similar pion mass spectra and reproduce the expected asymptotic behavior, their predictions for the hadronic light-by-light contribution exhibit sizable variations, driven by differences in the transition form factor in the low momentum transfer $Q^{2}$ region.

hep-ph↗

arXiv2026

Study of transition form factors of the lightest pseudoscalars

In this paper, we study the transition form factors of the lightest pseudoscalar mesons, $π^0$, $η$, and $η'$, within the framework of resonance chiral theory. Our analysis is performed based on the data of time-like and space-like singly-virtual and space-like doubly-virtual form factors, as well as the relevant cross sections and latest invariant mass spectra of $e^+e^-$ pair for the process of $P\toγe^+ e^-$. The transition form factors of these pseudoscalars are obtained. Also, we evaluate their contributions to the light-by-light part of the anomalous magnetic moment of the muon. Our two Fits give similar results, where Fit-A gives $a_μ^{π^0 }=(61.6\pm 1.8)\times10^{-11}$, $a_μ^{η}=(15.2\pm1.7)\times10^{-11}$, $a_μ^{η'}=(16.0\pm 1.2)\times10^{-11}$, and the total contribution of neutral pseudo-scalar meson poles is $a_μ^{π^0+η+η'}=(92.8\pm2.9)\times10^{-11}$.

hep-ph↗

arXiv2026

On the quantum numbers of the $X(1880)$

We study the properties of the $X(1880)$, the structure around the $\bar{p}p$ threshold that appears in the $3(π^+π^-)$ invariant mass spectrum in the decay process of $J/ψ\to γ3(π^+π^-)$. Nucleon-antinucleon rescattering is taken into account in our analysis, and the decay amplitude of $J/ψ\to γ3(π^+π^-)$ can be obtained by the distorted wave Born approximation. With these amplitudes, we analyze the contributions to the $X(1880)$ from different partial waves. Our analysis suggests that the $X(1880)$ should be isoscalar $0^{-+}$, and it is generated by the threshold behavior.

hep-ph↗

arXiv2025

An anlaysis on $J/ψ\toπ^0γ^*$ within resonance chiral theory

In this study, we analyze the first measurement of the electron-positron invariant mass spectrum in $J/ψ\to π^0 e^+e^-$ by BESIII, using the framework of resonance chiral theory. Our results indicate that both strong interaction and electromagnetic transition are essential to accurately describe the data. We obtain the $π^0$ transition form factor for $J/ψ\to π^0γ^*$ and the corresponding decay branching ratios for $J/ψ\to π^0 l^+l^-$. The decay process $J/ψ\to π^0 V$ is also examined. It is found that $J/ψ\to π^0 ρ^0$ is dominated by the strong interaction, while the other two channels, $J/ψ\to π^0 ω$ and $π^0 ϕ$, arise primarily from electromagnetic transitions.

hep-ph↗

arXiv2025

Conceptual Design of the Muonium-to-Antimuonium Conversion Experiment (MACE)

The spontaneous conversion of muonium to antimuonium is one of the interesting charged lepton flavor violation phenomena offering a sensitive probe of potential new physics and serving as a tool to constrain the parameter space beyond the Standard Model. The Muonium-to-Antimuonium Conversion Experiment (MACE) is designed to utilize a high-intensity muon beam, a Michel electron magnetic spectrometer, a positron transport system, and a positron detection system, to either discover or constrain this rare process with a conversion probability of $\mathcal{O}(10^{-13})$. This article presents an overview of the theoretical framework as well as a detailed description of the experimental design for the search for muonium-to-antimuonium conversion.

hep-ex↗

arXiv2025

Study of electron-positron annihilation into $K\bar{K}π$ within resonance chiral theory

In this paper, a coherent study of the $e^+e^-$ annihilation into $K^+K^-π^0$, $K^0_SK^0_Lπ^0$ and $K^0_SK^\pmπ^\mp$ is carried out within the framework of resonance chiral theory. The amplitudes are fixed by fitting to the experimental cross-section and invariant mass spectrum. With these amplitudes, one can calculate the hadronic vacuum polarization form factors of these processes. The leading order contributions of $σ(e^+e^- \to K\bar{K}π)$ to the anomalous magnetic moment of the muon, $(g-2)_μ$, is obtained as $a_μ^{\rm HVP,LO}(e^+e^- \to K\bar{K}π)=(3.178\pm0.071)\times10^{-10}$ up to $E_{\rm cm}=2.3$ GeV.

hep-ph↗

arXiv2024

New insights into the doubly charmed exotic mesons

Using effective Lagrangians constrained by the heavy quark spin symmetry and chiral symmetry, for the light quarks, we analyze the $D^0 D^0π^+$, $\bar{D}^0D^0π^0$ and $D^0\bar{D}^{*0}$ invariant mass spectra. Performing a simultaneous analysis of the doubly charmed and charm-anti-charm states gives further insights into the nature of the $T^+_{cc}$ and $χ^0_{c1}(3872)$, exotic hadrons. It is confirmed that both states should lie below their respective $DD^*$/$D\bar{D}^*$ thresholds. Also, the contributions of the triangle and box diagrams are negligible.

hep-ph↗

arXiv2024

Electromagnetic form factors of hyperons in the timelike region: A short review

We review recent experimental and theoretical results for the electromagnetic form factors of hyperons (Y) in the timelike region, accessible in the reactions $e^+e^-\to \bar YY$. Specifically, we focus on the final states $\bar ΛΛ$, $\barΛΣ^0$/$\bar Σ^0Λ$, $\bar ΣΣ$, $\bar ΞΞ$, and $\barΩΩ$. The $\bar Λ_cΛ_c$ system is also discussed.

hep-ph↗

arXiv2024

Heterogeneous network and graph attention auto-encoder for LncRNA-disease association prediction

The emerging research shows that lncRNAs are associated with a series of complex human diseases. However, most of the existing methods have limitations in identifying nonlinear lncRNA-disease associations (LDAs), and it remains a huge challenge to predict new LDAs. Therefore, the accurate identification of LDAs is very important for the warning and treatment of diseases. In this work, multiple sources of biomedical data are fully utilized to construct characteristics of lncRNAs and diseases, and linear and nonlinear characteristics are effectively integrated. Furthermore, a novel deep learning model based on graph attention automatic encoder is proposed, called HGATELDA. To begin with, the linear characteristics of lncRNAs and diseases are created by the miRNA-lncRNA interaction matrix and miRNA-disease interaction matrix. Following this, the nonlinear features of diseases and lncRNAs are extracted using a graph attention auto-encoder, which largely retains the critical information and effectively aggregates the neighborhood information of nodes. In the end, LDAs can be predicted by fusing the linear and nonlinear characteristics of diseases and lncRNA. The HGATELDA model achieves an impressive AUC value of 0.9692 when evaluated using a 5-fold cross-validation indicating its superior performance in comparison to several recent prediction models. Meanwhile, the effectiveness of HGATELDA in identifying novel LDAs is further demonstrated by case studies. the HGATELDA model appears to be a viable computational model for predicting LDAs.

cs.LG↗

arXiv2024

Study of the electromagnetic form factors of the nucleons in the timelike region

The electromagnetic form factors $G_{\rm E}$ and $G_{\rm M}$ of the proton and neutron in the timelike region are extracted in a study of the processes $e^+ e^-\to \bar{p}p$ and $e^+ e^-\to \bar{n}n$. The reaction amplitude is evaluated within the distorted wave Born approximation, with the interaction of the antinucleon-nucleon ($\bar{N}N$) pair taken into account. The latter is constructed within $SU(3)$ chiral effective field theory up to the next-to-leading order. An excellent description of the $e^+ e^-\to \bar{N}N$ data in the energy region from the $\bar{N}N$ threshold up to center-of-mass energies $E_{\rm cm}=2.2$~GeV is achieved. Results for the electromagnetic form factors $G_{\rm E}, G_{\rm M}$, $G_{\rm E}/G_{\rm M}$, and the subtracted effective form factors, $G_{\rm osc}$, are provided. These can be helpful for further studies of the properties of the nucleons.

nucl-th↗

arXiv2024

Study of the timelike electromagnetic form factors of the $Λ_c$

In this paper, the reaction of electron-positron annihilation into $Λ_c^+\barΛ_c^-$ is investigated. The $Λ_c^+\barΛ_c^-$ scattering amplitudes are obtained by solving the Lippmann-Schwinger equation. The contact, annihilation, and two pseudoscalar-exchange potentials are taken into account in the spirit of the chiral effective field theory. The amplitudes of $e^+e^-\to Λ_c^+\barΛ_c^-$ are constructed by the distorted wave Born approximation method, with the final state interactions of the $Λ_c^+\barΛ_c^-$ re-scattering implemented. By fitting to the experimental data, the unknown couplings are fixed, and high-quality solutions are obtained. With these amplitudes, the individual electromagnetic form factors in the timelike region, $G_E^{Λ_c}$, $G_M^{Λ_c}$, and their ratio, $G_E^{Λ_c}/G_M^{Λ_c}$, are extracted. Both modulus and phases are predicted. These individual electromagnetic form factors reveal new insights into the properties of the $Λ_c$. The separated contributions of the Born term, contact, annihilation, as well as the two pseudoscalar exchange potentials to the electromagnetic form factors are isolated. It is found that the Born term dominates the whole energy region. The contact term plays a crucial role in the enhancement near the threshold, and the annihilation term is essential in generating the fluctuation of the electromagnetic form factors.

hep-ph↗

arXiv2024

Strong decays of $T_{c\bar s0}(2900)^{++/0}$ as a fully open-flavor tetraquark state

We have studied the strong decay properties of the recently observed $T^a_{c\bar s0}(2900)^{++/0}$ by considering it as a $cu\bar{d}\bar{s}/cd\bar{u}\bar{s}$ fully open-flavor tetraquark state with $I(J^P)=1(0^+)$. In the framework of QCD sum rules, we have calculated the three-point correlation functions of the two-body strong decay processes $T^a_{c\bar s0}(2900)^{++}\rightarrow D_s^+π^+$, $D^+K^+, D_s^{\ast +}ρ^+$ and $D_{s1}^+π^+$. The full width of $T^a_{c\bar s0}(2900)^{++/0}$ is obtained as $161.7\pm94.8$ MeV, which is consistent with the experimental observation. We predict the relative branching ratios as $Γ(T\rightarrow D_sπ):Γ(T\rightarrow DK):Γ(T\rightarrow D_s^{\ast} ρ):Γ(T\rightarrow D_{s1}π)\approx1.00:1.10:0.04:0.43$, implying that the main decay modes of $T^a_{c\bar s0}(2900)^{++/0}$ state are $D_sπ$ and $DK$ channels in our calculations. However, the $P$-wave decay mode $D_{s1}π$ is also comparable and important by including the uncertainties. To further identify the nature of $T^a_{c\bar s0}(2900)^{++/0}$, we suggest confirming them in the $DK$ and $D_{s}π$ final states, and measuring the above ratios in future experiments.

hep-ph↗

arXiv2023

New insights into the oscillation of the nucleon electromagnetic form factors

The electromagnetic form factors of the proton and the neutron in the timelike region are investigated. Electron-positron annihilation into antinucleon-nucleon ($\bar NN$) pairs is treated in distorted wave Born approximation, including the final-state interaction in the $\bar NN$ system. The latter is obtained by a Lippmann-Schwinger equation for $\bar{N}N$ potentials derived within SU(3) chiral effective field theory. By fitting to the phase shifts and (differential) cross section data, a high quality description is achieved. With these amplitudes, the oscillations of the electromagnetic form factors of the proton and the neutron are studied. It is found that each of them can be described by two fractional oscillators. One is characterized as \lq overdamped' and dominates near the threshold, while the other is \lq underdamped' and plays an important role in the high-energy region. These two oscillators are essential to understand the distributions of polarized electric charges induced by hard photons for the nucleons.

nucl-th↗

arXiv2023

Two body final states production in electron-positron annihilation and their contributions to $(g-2)_μ$

In this paper, we study the processes of $e^{+}e^{-}$ annihilation into two body final states, either two pseudoscalar mesons or one meson with a photon. The hadronic vacuum polarization form factors are calculated within the framework of resonance chiral theory in the energy region of $E \lesssim 2$ GeV, with final state interactions taken into account. A joint analysis on the processes of $e^{+}e^{-} \rightarrow π^{+}π^{-}$, $K^{+}K^{-}$, $K_{L}^{0}K_{S}^{0}$, $π^{0}γ$, and $ηγ$ has been performed, and the latest experimental data are included. Based on the vacuum polarization form factors of these processes, we estimate their contributions to the lowest order of anomalous magnetic moment of the muon, $(g-2)_μ$. Combined with other contributions from hadronic vacuum polarization and other interactions from the standard model, the discrepancy between theoretical prediction and experimental measurement is $Δa_μ=(24.1\pm5.4)\times 10^{-10}$, i.e., 4.5$σ$.

hep-ph↗

arXiv2023

Study of $X(6900)$ with unitarized coupled channel scattering amplitudes

In this paper, we study the resonant state $X(6900)$. The scattering amplitudes of coupled channels, $J/ψJ/ψ$-$J/ψψ(2S)$-$J/ψψ(3770)$, are constructed with the interaction of four vector mesons described by effective Lagrangians. The amplitudes are calculated up to one loop, decomposed by partial wave projection, and unitarized by Pad$\acute{e}$ approximation. These amplitudes are fitted to the latest experimental data sets of di-$J/ψ$ and $J/ψψ(2S)$ invariant mass spectra of LHCb, CMS, and ATLAS. High-quality solutions are obtained. With these partial wave amplitudes, we extract the pole parameters of the $X(6900)$. Its quantum number is likely to be $0^{++}$. According to the pole counting rule as well as analysis of the phase shifts of the partial waves, it supports our previous conclusion that the $X(6900)$ prefers to be a compact tetra-quark.

hep-ph↗

arXiv2023

Structure around $p\bar{p}$ threshold in $J/ψ$ radiative decays

In this paper, we study the structure around the $p\bar{p}$ threshold that appears in $η'π^+π^-$, $3(π^+π^-)$ and $K_S^0K_S^0η$ invariant mass spectra in the processes of relevant $J/ψ$ radiative decays. The $N\bar{N}$ rescattering is taken into account, and the distorted-wave Born approximation is applied to get the decaying amplitude through a two-step process: $J/ψ\toγN\bar{N}\toγη'π^+π^-$, $γ3(π^+π^-)$ and $γK_S^0K_S^0η$. The $N\bar{N}$ scattering amplitudes are obtained by solving the Lippmann-Schwinger equation with the potentials given by chiral effective field theory. To fix the unknown couplings, we fit the amplitudes to the datasets of the latest measurements on the invariant mass spectra of $J/ψ$ radiative decays, as well as the phase shifts and inelasticities given by partial wave analysis. We vary the cutoffs ($R$=0.9, 1.0, and 1.1 fm) and find that the solutions are stable. The structures around $p\bar{p}$ threshold found in the processes of $J/ψ\toγη'π^+π^-$, $J/ψ\to\gamma3(π^+π^-)$ and $J/ψ\toγK_S^0K_S^0η$ can be attributed to threshold behavior of $N\bar{N}$ intermediate states.

hep-ph↗