arXiv subjects

Si-Wei Liu

Publications and source records attributed to Si-Wei Liu.

12 recordsLinked to original sources

arXiv2026

Study of the $e^+e^- \to ϕK^+K^-$ reaction within triangle dynamics and its implications for the $ϕ(2170)$

We revisit the $e^+e^- \to ϕπ^+π^-$ reaction within the $K_1$-$\bar{K}$-$K$ triangle dynamics framework, in which the $e^+e^-$ pair annihilates through one-photon exchange approximation to produce a $K_1\bar{K}$ pair, followed by the $K_1 \toϕK$ decay and the final-state $K\bar{K} \to π^+π^-$ rescattering. With the same theoretical formalism and model parameters, the $e^+e^- \to ϕK^+K^-$ reaction is investigated, and it is found that the predicted total cross sections for the $e^+ e^- \to ϕK^+ K^-$ reaction are in good agreement with the existing BESIII measurements. Our study shows that the triangle singularity in the $ϕK^+K^-$ channel is strongly suppressed, because the higher $K^+K^-$ mass threshold shifts the kinematics away from the triangle singularity condition and the phase space near the $K_1\bar{K}$ threshold is very limited. Moreover, the interference between the tree-level and loop amplitudes eliminates the remaining signal. These combined effects naturally explain the absence of a distinct $ϕ(2170)$ signal in the $e^+ e^- \to ϕK^+ K^-$ reaction, provide a strong test of the model, and reinforce the picture that both reactions are governed by the same underlying mechanism, in which the $ϕ(2170)$ state is produced in the $e^+ e^-$ annihilation from the $K_1$-$\bar{K}$-$K$ triangle loop.

hep-ph↗

arXiv2026

Unveiling the elusive $Σ(1380)$ resonance through coupled-channel dynamics in $Λ_c^+\toηπ^+Λ$ reaction

We investigate the $Λ_c^+ \to ηπ^+ Λ$ decay measured by the Belle and BESIII Collaborations, focusing on the possible role of the $Σ(1380)$ state with spin-parity $J^P=1/2^-$. In our theoretical framework, the $Λ(1670)$ and $a_0(980)$ are dynamically generated from meson-baryon and meson-meson final-state interactions, respectively, and the corresponding line shapes of these two states used here are applicable to all relevant hadronic reactions. Furthermore, the contributions from the intermediate $Σ(1385)$ resonance and the possible $Σ(1380)$ state are included explicitly. By comparing the invariant mass and angular distributions obtained with and without the $Σ(1380)$ state, we demonstrate that this state plays an important role in improving the description of the experimental data. We also identify the kinematic regions most sensitive to the possible $Σ(1380)$ contribution. Future high-precision measurements of this process will be instrumental for testing the existence of the $Σ$ state with $J^P=1/2^-$.

hep-ph↗

arXiv2026

Final-state rescattering mechanism of the $Δ(1232)^{++}$ production in $Λ^+_c \to K^- π^+ p$ decay

We investigate the production of the $Δ(1232)^{++}$ resonance in the charmed baryon weak decay $Λ^+_c \to K^- π^+ p$, focusing on the $π^+ p$ final-state rescattering mechanism. The direct $W^+$ exchange diagram is expected to be suppressed, hence we adopt the $W^+$ internal emission process $Λ^+_c \to p \bar K^{*0}(892)$ followed by the subsequent decay $\bar{K}^{*0} \to K^- π^+$ as the dominant source of the final state particles. The $Δ(1232)^{++}$ resonance is then generated via $π^+ p$ rescattering within a triangle loop mechanism. Our calculations incorporate both the tree-level $\bar K^{*0}(892)$ and the dynamically generated $\bar{K}^*_0(700)$ state arising from the $S$-wave $K π$ final state interaction. We find that our theoretical results can reproduce the bump and peak structures in the $K^- π^+$ invariant mass distributions for the $\bar{K}^*_0(700)$ and $\bar{K}^{*0}(892)$, respectively. Meanwhile, the peak for the $Δ(1232)^{++}$ in the $π^+ p$ invariant mass distributions is also well described. The $Δ(1232)^{++}$ signal naturally emerges from rescattering effects, and adopting the pole parameters of $Δ(1232)$ resonance yields an improved description of the experimental data. In addition, we obtain a branching fraction ratio $\mathcal{B}[Λ_c^+ \to Δ(1232)^{++} K^-] / \mathcal{B}[Λ_c^+ \to p \bar{K}^{*0}(892)] \approx 0.5$, which is lower than the experimentally measured value. This discrepancy suggests that interference effects are likely significant in this decay process. Future high-precision measurements will further verify the proposed rescattering mechanism.

hep-ph↗

arXiv2026

Probing the hadronic molecular nature of the $Ω(2012)$, $Ω(2380)$, and $Ω_c(3120)$ via femtoscopy correlation functions

We investigate the femtoscopic correlation functions of systems associated with the $Ω(2012)$, $Ω(2380)$, and $Ω_c(3120)$ resonances, with the aim of elucidating their internal structures. By employing effective potential models that incorporate both $s$-wave and $d$-wave interactions, we calculate the correlation functions for the relevant coupled channels. Our numerical results reveal pronounced enhancement structures in the $Ξ^0K^-$ and $Ξ_c^+K^-$ correlation functions, which provide direct evidences for the dynamically generated $Ω(2012)$ and $Ω_c(3120)$ states. Furthermore, significant low-momentum enhancements are observed in the $Ξ^{*0}K^-$ and $Ξ^{*0}K^{*-}$ channel, which are attributed to the $Ω(2012)$ and $Ω(2380)$ resonances. These theoretical calculations provide crucial insights for future high-precision measurements at the LHC and RHIC, offering a novel and independent approach to determine the dynamically generated hadronic molecular nature of these $Ω$ excited states.

hep-ph↗

arXiv2026

Femtoscopic correlation functions for general partial waves: Application to the $Λ(1520)$ resonance

The femtoscopic correlation function has been established in recent years as a high-precision tool for investigating hadron-hadron interactions and exotic states, providing stringent constraints on the dynamics of low-energy strong interactions. However, current research has been predominantly focused on the $s$-wave interaction between hadrons, while studies of higher partial waves remain scarce. We present a general analytical expression for the femtoscopic correlation function in an arbitrary partial wave using the Lippmann-Schwinger equation. This formalism is applied to constrain the $d$-wave $K^-p$ scattering through a combined study of the $K^-p$ correlation function and the $D_{03}$ scattering amplitude of $\bar K N \to \bar K N$ and $\bar K N \to πΣ$ processes, from which the properties of $Λ(1520)$ are extracted and found to be in good agreement with the experimental results. These findings demonstrate the feasibility of determining dynamics between hadrons through femtoscopic correlation functions and scattering amplitudes with higher partial waves.

hep-ph↗

arXiv2026

Role of $Σ(1660)$ in the $K^- p \toπ^0π^0Σ^0$ reaction

The processes of $K^-p \to π^0 π^0 Σ^0$ and $K^- p \to π^0 Λ(1405)$ are studied within the effective Lagrangian approach. In addition to the ``background" contribution from the $u$-channel nucleon pole term, contribution from the $Σ(1660)$ resonance with spin-parity $J^P=1/2^+$ is also considered. For the $K^-p \to π^0 π^0 Σ^0$ reaction, we perform a calculation for the total and differential cross sections by considering the contribution from the $Σ(1660)$ intermediate resonance decaying into $π^0 Λ(1405)$ with $Λ(1405)$ decaying into $π^0 Σ^0$. With our model parameters, the available experimental data on both the $K^-p \to π^0 π^0 Σ^0$ and $K^- p \to π^0 Λ(1405)$ reactions can be fairly well reproduced. It is shown that we really need the contribution from the $Σ(1660)$ resonance, and that these experimental measurements could be used to determine some properties of the $Σ(1660)$ resonance.

hep-ph↗

arXiv2025

RAMS: Residual-based adversarial-gradient moving sample method for scientific machine learning in solving partial differential equations

Physics-informed neural networks (PINNs) and neural operators, two leading scientific machine learning (SciML) paradigms, have emerged as powerful tools for solving partial differential equations (PDEs). Although increasing the training sample size generally enhances network performance, it also increases computational costs for physics-informed or data-driven training. To address this trade-off, different sampling strategies have been developed to sample more points in regions with high PDE residuals. However, existing sampling methods are computationally demanding for high-dimensional problems, such as high-dimensional PDEs or operator learning tasks. Here, we propose a residual-based adversarial-gradient moving sample (RAMS) method, which moves samples according to the adversarial gradient direction to maximize the PDE residual via gradient-based optimization. RAMS can be easily integrated into existing sampling methods. Extensive experiments, ranging from PINN applied to high-dimensional PDEs to physics-informed and data-driven operator learning problems, have been conducted to demonstrate the effectiveness of RAMS. Notably, RAMS represents the first efficient adaptive sampling approach for operator learning, marking a significant advancement in the SciML field.

cs.CE↗

arXiv2025

Neural-operator element method: Efficient and scalable finite element method enabled by reusable neural operators

The finite element method (FEM) is a well-established numerical method for solving partial differential equations (PDEs). However, its mesh-based nature gives rise to substantial computational costs, especially for complex multiscale simulations. Emerging machine learning-based methods (e.g., neural operators) provide data-driven solutions to PDEs, yet they present challenges, including high training cost and low model reusability. Here, we propose the neural-operator element method (NOEM) by synergistically combining FEM with operator learning to address these challenges. NOEM leverages neural operators (NOs) to simulate subdomains where a large number of finite elements would be required if FEM was used. In each subdomain, an NO is used to build a single element, namely a neural-operator element (NOE). NOEs are then integrated with standard finite elements to represent the entire solution through the variational framework. Thereby, NOEM does not necessitate dense meshing and offers efficient simulations. We demonstrate the accuracy, efficiency, and scalability of NOEM by performing extensive and systematic numerical experiments, including nonlinear PDEs, multiscale problems, PDEs on complex geometries, and discontinuous coefficient fields.

cs.CE↗

arXiv2025

Studying the $KΛ$ strong interaction with femtoscopic correlation functions and the $N^*(1535)$

We investigate the $K Λ$ strong interaction dynamics around the energy region of $N^*(1535)$ resonance through femtoscopic correlation functions within the Koonin-Pratt formalism, where coupled-channel effects of $πN$, $KΛ$, $K Σ$ and $ηN$ channels are taken into account, by means of which the $N^*(1535)$ resonance can be dynamically generated in the chiral unitary approach. Two-body scattering amplitudes are calculated using the chiral unitary approach, and the corresponding wave functions and correlation functions are obtained. Our analysis shows that the $πN$ channel becomes important to the $K^+Λ$ correlation function through coupled channel effects, even if its mass threshold is far from the energy region of the $N^*(1535)$. Furthermore, with the picture that the $N^*(1535)$ is a dynamically generated state, we can get a good reproduction of the experimental data on the $K^+Λ$ correlation function. This work establishes femtoscopic correlation functions as a sensitive probe for coupled-channel dynamics and validates the Koonin-Pratt framework in multi-channel hadronic systems, offering critical insights into some exotic hadron states and strong interaction mechanisms.

hep-ph↗

arXiv2025

Roles of $Δ(1232)$, $N^(1520)$, and $N^(1650)$ resonances in $γp\to π^0 π^0 p$ reaction within an effective Lagrangian approach

Roles of the $Δ(1232)$, ${N}^{*}(1520)$, and ${N}^{*}(1650)$ resonances in the $γp\to{π}^{0}{π}^{0}p $ reaction near threshold is investigated within an effective Lagrangian approach. We have calculated the differential cross sections of the $γp\to{π}^{0}{π}^{0}p$ reaction by including the contributions from the $Δ(1232)$, ${N}^{*}(1520)$, and ${N}^{*}(1650)$ intermediate states decaying into $π^0 p$ via the $s$-channel nucleon pole and $t$-channel $ρ$ exchange, and found that the current experimental measurements can be well reproduced. The production of $Δ(1232)$ is mainly from the mechanism of the $s$-channel nucleon pole, while the ${N}^{*}(1520)$ and ${N}^{*}(1650)$ are produced from the mechanism of the $t$-channel $ρ$ exchange. It is expected that more experimental data on the $γp \to π^0 π^0 p$ reaction can be used to explore the properties of the low-lying excited baryon states and also the scalar $f_0(500)$ and $f_0(980)$ mesons.

hep-ph↗

arXiv2024

Theoretical study of $N(1535)$ and $Σ^*(1/2^-)$ in the Cabibbo-favored process $Λ_c^+ \to p \bar{K}^0η$

Motivated by the recent experimental measurements, we have investigated the Cabibbo-favored process $Λ_c^+ \to p \bar{K}^0η$, where the $N(1535)$ resonance is dynamically generated from the $S$-wave pseudoscalar meson-octet baryon interactions within the chiral unitary approach. The contributions from the intermediate $N(1650)$ and the predicted low-lying baryon $Σ^*(1/2^-)$ are also considered. In addition, a Breit-Wigner amplitude for the $N(1535)$ resonance is checked. By comparing with the measured $ηp$, $\bar{K}^0 η$, and $p \bar{K}^0$ invariant mass squared distributions, our results support the interpretation of $N(1535)$ as a dynamically generated state. Furthermore, we demonstrate that, with the contribution from $Σ^*(1/2^-)$ taken into account, the calculated invariant mass spectrum agrees with the Belle measurements. Future precise measurements of the $Λ_c^+\to p \bar{K}^0η$ process can further elucidate the existence of the low-lying baryon $Σ^*(1/2^-)$.

hep-ph↗

arXiv2023

Theoretical study on $Λ_c^+ \to ΛK^+\bar{K}^0$ decay and $Ξ^*(1690)$ resonance

We present a theoretical study of $Ξ^*(1690)$ resonance in the $Λ_c^+ \to ΛK^+ \bar{K}^0$ decay, where the weak interaction part proceeds through the Cabibbo-favored process $c \to s + u\bar{d}$. Next, the intermediate two mesons and one baryon state can be constructed with a pair of $q\bar{q}$ with the vacuum quantum numbers. Finally, the $Ξ^*(1690)$ is mainly produced from the final state interactions of $\bar{K}Λ$ in coupled channels, and it is shown in the $\bar{K}Λ$ invariant mass distribution. Besides, the scalar meson $a_0(980)$ and nucleon excited state $N^*(1535)$ are also taken into account in the decaying channels $K^+\bar{K}^0$ and $K^+Λ$, respectively. Within model parameters, the $K^+ \bar{K}^0$, $\bar{K}^0 Λ$ and $K^+ Λ$ invariant mass distributions are calculated, and it is found that our theoretical results can reproduce well the experimental measurements, especially for the clear peak around $1690$ MeV in the $\bar{K}Λ$ spectrum. The proposed weak decay process $Λ_c^+ \to ΛK^+ \bar{K}^0$ and the interaction mechanism can provide valuable information on the nature of the $Ξ^*(1690)$ resonance.

hep-ph↗