arXiv subjects

Ju-Jun Xie

Publications and source records attributed to Ju-Jun Xie.

At least 19 recordsLinked to original sources

arXiv2026

Implication of the observed $ψ(3770)\to p\bar{p}π^0$ for studying the $p\bar{p}\to ψ(3770)π^0$ process

We study the charmonium $p \bar{p} \to ψ(3770) π^0$ reaction using the effective lagrangian approach where the contributions from well established $N^*$ states are considered, and all parameters are fixed in the process of $e^+e^- \to p \bar{p}π^0$ at center of mass energy $\sqrt{s} = 3.773$ GeV. The experimental data on the line shape of the mass distribution of the $e^+e^- \to p\bar{p}π^0$ can be well reproduced. Based on the studying of $e^+e^- \to p \bar{p}π^0$, the total and differential cross sections of the $p \bar{p} \to ψ(3770) π^0$ reaction are predicted. At the same time we evaluated also the cross sections of the $p \bar{p} \to ψ(3686) π^0$ reaction. It is shown that the contribution of the nucleon pole to this reaction is largest from the reaction threshold within a wide range. However, the interference between nucleon pole and the other nucleon resonance can still change the angle distributions significantly. Those theoretical results may be test by the future experiments at $\overline{\mbox{P}}$ANDA.

hep-ph↗

arXiv2026

Electromagnetic form factors of singly charmed baryons $Σ_c$ and $Λ_c$ in a covariant quark-diquark model

We present a systematic study of the spacelike electromagnetic form factors of the ground-state singly charmed baryons, $Σ_c$ ($Σ_c^{++},Σ_c^+,Σ_c^0$) and $Λ_c^+$, within a covariant quark-diquark model. Based on this framework, we obtain their magnetic moments as well as electric charge and magnetic moment radii. Such observables are important to understand the internal structure and the inner dynamics of these heavy baryon states. Our theoretical calculations are in qualitative agreement with available lattice QCD results of $Σ_c^{++}$ and $Σ_c^0$ baryons. We also discuss the mechanism behind the dependence of the numerical results on the charm quark and light diquark. A key finding is that the electric form factors of the singly charmed baryons fall off much more slowly with momentum transfer $Q^2$ than that of the proton, indicating a more compact electric charge distribution, which is attributed to the heavy charm quark acting as a localized core. More importantly, we observe a striking difference in the magnetic structure: while the magnetic form factors of $Σ_c$ are dominated by the light axial-vector diquark, those of $Λ_c^+$ are unexpectedly governed by the charm quark due to the vanishing contribution of the scalar diquark. This highlights the decisive role of the light-diquark spin configuration in determining the magnetic properties. Finally, using an empirical asymptotic relation connecting the spacelike and timelike regions, we predict the total cross section for $e^+e^-\toΣ_c\barΣ_c$. Our findings can be tested at existing facilities including the BESIII, Belle II and LHCb, as well as the proposed Super Tau-Charm Facility.

hep-ph↗

arXiv2026

Singly Cabibbo-suppressed hadronic weak decays of the $Ω^-$ hyperon

We study the two-body hadronic weak decays of the $Ω^-$ hyperon with strangeness $S=-3$, including three singly Cabibbo-suppressed decay modes: $Ξ^0 π^-$, $Ξ^-π^0$ and $ΛK^-$. The decay amplitudes at the quark level, arising from $s\to ud \bar{u}$ transitions (direct pion emission and color-suppressed processes) and $su\to ud$ transitions (pole terms), are calculated in the framework of the non-relativistic constituent quark model.The theoretical results show that the $Ξ^0 π^-$ channel is dominated by the color-allowed direct pion emission process, while the $ΛK^-$ channel is well described by one type of pole contribution mediated through intermediate $Ξ$ resonances ($1^2S_{1/2^+}$ and $1^2P_{1/2^-}$ states). However, the contribution from tree-level mechanisms alone to the branching ratio of $Ω^- \to Ξ^- π^0$ is small due to its color-suppressed nature. The discrepancy is resolved by including final state interactions through rescattering processes via intermediate states $Ξ^0π^-$ and $ΛK^-$. This work demonstrates that a unified description of $Ω^-$ hadronic weak decays necessitates the interplay of quark-level weak vertices, baryon pole structures, and long-distance final state rescattering dynamics. With these mechanisms, the obtained branching ratios are in agreement with the high-precision experimental data from the BESIII. Furthermore, these above decays are found to be dominated by the parity-conserving $P$-wave transitions, thus the asymmetry parameters are almost zero.

hep-ph↗

arXiv2026

Role of $K^*_0(700)$ exchange in the $p \bar{p} \to Λ\barΛ$ reaction

Based on the effective Lagrangian approach, we investigate the $p \bar{p} \to Λ\barΛ$ reaction. Within this framework, we provide a dynamical explanation by analyzing its total and differential cross sections, as well as the polarization of the produced $Λ$ hyperon. Incorporating the $t$-channel exchange of the scalar $K^*_0(700)$ and pseudoscalar $K$ mesons, complemented by an $s$-channel contribution from the vector excited state, we can reproduce the current experimental data fairly well in a wide energy region. Compared to the conventional $K$ and $K^*(892)$ mesons exchange, the $K^*_0(700)$ meson exchange plays a more essential role in simultaneously capturing the observed features of the total and differential cross sections. The introduction of the vector $s$-channel resonance improves the description of the spin observables. This work gives a perspective to inspect the role of $K^*_0(700)$ and serves as a test to search for the resonances in the reaction $p \bar{p} \to Λ\barΛ$ at threshold.

hep-ph↗

arXiv2026

Generalizing the Soffer Bound: Positivity Constraints on Parton Distributions of Spin-3/2 Particles

We derive the complete set of positivity bounds for the leading-twist parton distribution functions (PDFs) of a spin-3/2 hadron for the first time. This work generalizes the Soffer bound, a fundamental constraint for spin-1/2 nucleons, to quark and gluon distribution functions in higher-spin systems. Expressing the antiparton-hadron scattering amplitudes in terms of the PDFs and the spin density matrix, we establish the connections between the PDFs and the scattering amplitudes in the tensor product space of the parton and hadron spins. Moreover, we obtain the definitions of the PDFs in terms of the helicity amplitudes. Positive definiteness of the scattering amplitude matrix yields a set of inequalities that define the physically allowed parameter space for the helicity amplitudes and a set of constraints for the PDFs. The Cauchy-Schwartz inequality determines the constrains between the PDFs and generalized parton distributions.

hep-ph↗

arXiv2026

The dynamically generated $h_1$ state by the $K^\bar{K}^$ interaction and its $K_1(1270)\bar{K}$ and $b_1(1235)π$ decays

We investigate the dynamically generated $h_1$ state with spin-parity $J^P = 1^+$ and a mass around 1790~MeV, arising from the $K^* \bar{K}^*$ interaction within the chiral unitary approach. The partial decay widths into the $K_1(1270)\bar{K}$ and $b_1(1235)π$ channels are calculated via a triangular loop mechanism. In this mechanism, the $h_1$ state couples to $K^* \bar{K}^*$, and final-state interactions between $K^*$ and $\bar{K}^*$ proceed through pseudoscalar-meson exchange, leading to the final states $\bar{K}$ (or $π$) and $K_1(1270)$ [or $b_1(1235)$]. We also present the invariant mass distributions of a vector meson and a pseudoscalar meson originating from the decays of $K_1(1270)$ or $b_1(1235)$, along with the corresponding decay widths. Our results show that these decay widths are all of the order of a few MeV. We hope that future experiments can test the predictions presented here, thereby helping to identify this $h_1$ state.

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

Quantum dominance of coherent bremsstrahlung in $^{124}$Sn + $^{124}$Sn scattering at 25 MeV/u

We present quantum-mechanical calculations of bremsstrahlung in the $^{124}$Sn + $^{124}$Sn at 25 MeV/u reproducing the measured photon spectrum over the full energy range. For the first time, we quantitatively determine the incoherent-to-coherent ratio in the photon spectrum. This ratio is extremely small, ranging from $10^{-11}$ to $10^{-4}$, which demonstrates that coherent emission dominates throughout the measured energy range. This behavior is in sharp contrast to proton-nucleus scattering, where incoherent emission dominates because of the leading role of nucleon magnetic moments. This contrast is illustrated by the TAPS Collaboration data for $p + ^{197}{\rm Au}$ collisions at a proton beam energy of 190 MeV, where the corresponding ratio reaches $10^{3}$-$10^{5}$. We find that incoherent-to-coherent ratios explain the difference between the two spectra in unified picture: (1) In proton--nucleus scattering, the spectrum contains a pronounced hump, (2) In $^{124}$Sn + $^{124}$Sn scattering, the spectrum decreases monotonically and has a nearly logarithmic shape. Our results identify a previously unexplored quantum regime of bremsstrahlung emission in nuclear reactions and open a new route for studying coherent effects in heavy-ion collisions.

nucl-th↗

arXiv2026

Exploring the lifetime frontier with a beam-dump experiment at CiADS

We propose a beam-dump experiment (BDE) at the upcoming facility of China initiative Accelerator Driven System (CiADS), called CiADS-BDE, in order to search for long-lived particles (LLPs) predicted in various beyond-the-Standard-Model (BSM) theories. The experiment is to be located in the forward direction of the incoming low-energy proton beam at CiADS, leveraging the strong forward boost of the produced particles at the beam dump in general. The space between the dump and the detector is largely available, allowing for installation of shielding and veto materials and hence low levels of background events. We elaborate on the detector setup, and choose dark photon as a benchmark model for sensitivity study. We restrict ourselves to the signature of an electron-positron pair and perform detailed background estimates. We find that with 5 years' operation, unique, currently unexcluded parts of the parameter space for $\mathcal{O}(100)$~MeV dark-photon masses and $\mathcal{O}(10^{-9}\text{--}10^{-8})$ kinetic mixing can be probed at the CiADS-BDE. Furthermore, considering that there is no need to set up a proton beam specifically for this experiment and that the detector system requires minimal instrumentation, the experiment is supposed to be relatively cost-effective. Therefore, we intend this work to promote studies on the sensitivity reach of the proposed experiment to additional LLP scenarios, and in the end, the realization of the experiment. Incidentally, we study the sensitivity of the same BDE setups at the High Intensity Heavy-ion Accelerator Facility (HIAF), presently in operation near the CiADS program site, and conclude that HIAF-BDE could probe new parameter regions, too.

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

Study of $χ_{cJ}\to ηηη^\prime$ via intermediate charmed meson loop mechanisms and its implications for non-observation of $η_1(1855)$ in $χ_{cJ}$ decays

Recently, the BESIII Collaboration reported the first observation of the decays $χ_{cJ} \to ηηη^\prime$ in order to search for the $1^{-+}$ exotic state $η_1(1855)$. A partial wave analysis of the $ηη^\prime$ invariant mass spectrum shows no significant signal for the $η_1(1855)$. In this work, we, using an effective Lagrangian approach, investigate the processes $χ_{cJ} \to ηηη^\prime$ via the box and triangle loops involving charmed mesons and the scalar meson $f_0(1500)$. Our calculations reproduce well the experimental branching fractions of $χ_{cJ} \to ηηη^\prime$. Furthermore, we present the predictions of the relevant invariant mass spectra of $ηη^\prime$ and $ηη$ produced in the $χ_{c1}$ decay, which seem overall consistent with the BESIII measurements. In the present model, the decay $χ_{c1} \to ηηη^\prime$ is dominated by the triangle and box loop contributions. The consistency between our theoretical results and the BESIII measurements sheds light on the underlying decay mechanism of the $χ_{cJ}$ decaying into light mesons and might be helpful to understand the absence of the $η_1(1855)$ signal in the decay channels $χ_{cJ} \to ηηη^\prime$.

hep-ph↗

arXiv2026

The dynamically generated $N(1535)$ state in the $Λ_c^+ \to p\bar{K}^0 π^0$ decay

We present a theoretical analysis of the process $Λ_c^+ \to p\bar{K}^0 π^0$ within the chiral unitary approach, with particular emphasis on the dynamically generated $N(1535)$ resonance. In addition to $N(1535)$, our model incorporates contributions from other intermediate resonances including $N(1650)$, $K^*(892)$, $K_0^*(1430)$, $N(1440)$, and $Σ(1750)$. The calculated invariant mass distributions and Dalitz plot are in good agreement with the recent Belle measurements. Our analysis highlights the crucial role of $N(1535)$ state in this decay channel and supports its interpretation as a dynamically generated state arising from coupled-channel meson-baryon interactions.

hep-ph↗

arXiv2026

Spin polarization and quantum entanglement of baryon-antibaryon pairs produced in electron-positron annihilation

In this work, we systematically investigate the evolution of spin polarization and quantum entanglement in cascade decays of baryon-antibaryon pairs, which are produced in electron-positron annihilation. We derive a fully analytical spin density matrix explicitly expressed in terms of spin polarization observables, extend this formalism to multi-step cascade decay scenarios, and establish compact recursive relations to facilitate density matrix calculations for such processes. It is found that when maximal parity violation occurs during a decay, the resulting final-state particles are fully polarized and exist in a non-entangled state. Furthermore, we demonstrate that quantum entanglement amplification is a generic characteristic of charge-conjugate decays under $CP$ conservation when the initially produced baryon-antibaryon pair is polarized.

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

Radiative decays of the $Ω(2012)$ as a hadronic molecule

We present a theoretical investigation of the radiative decay process $Ω(2012) \to γΩ$, where the $Ω(2012)$ resonance with spin-parity $J^P=\frac{3}{2}^-$, is treated as a dynamically generated state from $\bar{K}Ξ(1530)$ and $ηΩ$ in $s$-wave and $\bar{K}Ξ$ in $d$-wave. The radiative decay width of the $Ω(2012)$ is calculated using a triangular loop mechanism, where the $Ω(2012)$ couples to the $\bar{K} Ξ(1530)$ channel. Subsequently, the final state interactions between $Ξ(1530)$ and $\bar{K}$ transition to a photon and $Ω$ through the exchange of a $Ξ$ baryon. Our calculations yield a radiative decay width of $13.2 ^{+4.5}_{-3.9}$ KeV, with uncertainties arising from the model parameters. This result provides valuable insights into the nature of the $Ω(2012)$ resonance and its decay dynamics. It is expected that the calculations presented here could be verified by future experiments, which would open a new door for studying the still elusive nature of the $Ω(2012)$.

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

Huizhou Hadron Spectrometer -- a Proposed High-rate Experimental Setup at the High Intensity Heavy-ion Accelerator Facility

The High-Intensity Heavy-Ion Accelerator Facility (HIAF), currently under construction in Huizhou, Guangdong Province, China, is projected to be completed by 2025. This facility will be capable of producing proton and heavy-ion beams with energies reaching several GeV, thereby offering a versatile platform for advanced fundamental physics research. Key scientific objectives include exploring physics beyond the Standard Model through the search for novel particles and interactions, testing fundamental symmetries, investigating exotic hadronic states such as di-baryons, pentaquark states and multi-strange hypernuclei, conducting precise measurements of hadron and hypernucleus properties, and probing the phase boundary and critical point of nuclear matter. To facilitate these investigations, we propose the development of a dedicated experimental apparatus at HIAF - the Huizhou Hadron Spectrometer (HHaS). This paper presents the conceptual design of HHaS, comprising a solenoid magnet, a five-dimensional silicon pixel tracker, a Low-Gain Avalanche Detector (LGAD) for time-of-flight measurements, and a Cherenkov-scintillation dual-readout electromagnetic calorimeter. The design anticipates an unprecedented event rate of 1-100 MHz, extensive particle acceptance, a track momentum resolution at 1% level, an electromagnetic energy resolution of ~3% @ 1 GeV and multi-particle identification capabilities. Such capabilities position HHaS as a powerful instrument for advancing experimental studies in particle and nuclear physics. The successful realization of HHaS is expected to significantly bolster the development of medium- and high-energy physics research within China.

hep-ex↗

arXiv2025

Violation of the elliptic flow scaling of $f_0(980)$ in p-Pb collisions at the LHC

We investigate the production and elliptic flow of the $f_0(980)$ in high-multiplicity p-Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV using a hadronic coalescence model with the $K$ and $\bar K$ phase-space distributions provided by the Hydro-Coal-Frag hybrid model. Our results, which agree with the ALICE and CMS measurements, support the $K\bar K$ molecular interpretation of the $f_0(980)$ structure and show, however, a breakdown of the simple number-of-constituent (NC) scaling of its elliptic flow. The latter is in contrast to the deuteron elliptic flow, which exhibits a significantly better NC scaling when the same coalescence width parameter is used.

nucl-th↗