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Xurong Chen

Publications and source records attributed to Xurong Chen.

At least 19 recordsLinked to original sources
arXiv2026

Orbital Angular Momentum as a Transverse Probe of Elliptic Small-$x$ Gluon Tomography

We propose a new way to probe elliptic small-$x$ gluon geometry in hard diffractive dijet deep inelastic scattering: a localized lepton wave packet carrying orbital angular momentum is used as a tunable transverse analyzer of the target. Unlike the conventional plane-wave setup, where the probe provides a fixed transverse projection, the OAM mode supplies additional radial and azimuthal structure while leaving the target dipole matrix element unchanged. We characterize the resulting elliptic response through $S_M=D_M-C_M$ and find finite-yield response nodes whose origin depends on the OAM channel. In the present benchmark, the $M=1$ crossing is associated mainly with a zero of the direct response, whereas the $M=3$ channel exhibits a nontrivial cancellation $D_3=C_3\neq0$. Signed transverse response densities show that this node results from a spatial cancellation rather than from a disappearance of the underlying scattering strength, and its position can be shifted by changing the beam--target offset. The specific sensitive value of $M$ depends on the analyzer profile and kinematics; the broader result is that localized OAM wave packets provide a controllable probe-side degree of freedom for small-$x$ gluon tomography.

hep-ph↗
arXiv2026

A Lawson-inspired Cycle-Closure Criterion for Deuterium--Tritium Muon-Catalyzed Fusion

Deuterium--tritium muon-catalyzed fusion is limited by a cycle-closure problem: a negative muon must complete enough catalytic cycles before decay or effective alpha sticking removes it from reuse. We formulate a Lawson-inspired criterion for this single-muon cycle. The effective cycle strength is defined as $\mathcal{L}_\mu=\Lambda_c\tau_\mu$, where $\Lambda_c$ is the effective cycle-completion rate and $\tau_\mu$ is the muon lifetime. Together with the residual effective sticking probability $\omega_S^{\rm eff}$, it gives the mean fusion yield per useful muon, $N_{\rm fus,\mu}=\mathcal{L}_\mu/(1+\omega_S^{\rm eff}\mathcal{L}_\mu)$. Introducing the useful D--T cycle energy $E_{\rm use}$, the system factor $\eta_{\rm sys}$, and the effective muon cost $E_\mu^{\rm cost}$, the one-muon gain is $G_\mu=(\eta_{\rm sys}E_{\rm use}/E_\mu^{\rm cost})N_{\rm fus,\mu}$. This leads to the required cycle strength $\mathcal{L}_\mu^{\rm req}=G_\mu N_L/(1-\omega_S^{\rm eff}G_\mu N_L)$, with $N_L=E_\mu^{\rm cost}/(\eta_{\rm sys}E_{\rm use})$, and to the conditional sticking boundary $\omega_S^{\rm eff}<1/(G_\mu N_L)$. The criterion separates rate-limited, sticking-limited, and cost-limited regimes in the $(\omega_S^{\rm eff},\mathcal{L}_\mu)$ plane. When representative historical D--T $\mu{\rm CF}$ anchors are projected onto this plane, they lie in a high-yield region but remain constrained by the effective-sticking boundary under conventional multi-GeV muon-cost accounting. The framework provides a compact diagnostic for assessing whether future improvements act mainly by increasing the effective cycle-completion rate, reducing residual sticking, or lowering the useful cost of delivered muons.

nucl-th↗
arXiv2026

Pion and Kaon PDFs via Infrared-Safe Evolution augmented by $J/\psi$ Data Constraints

Probing the partonic structure of the pion and the kaon provides essential insights into the non-perturbative dynamics of QCD, yet their parton distribution functions (PDFs) remain poorly constrained due to the scarcity of high-precision experimental data, especially for the gluon distributions. We present an improved determination of pion and kaon PDFs within the dynamical parton model combined with the maximum entropy method (MEM) framework. Our analysis features two key advancements: firstly, we employ an infrared-safe QCD evolution scheme, allowing the evolution to be reliably extended down to very low $Q^2$, approaching the hadronic scale; secondly, we incorporate pion- and kaon-induced $J/\psi$ hadroproduction data as crucial constraints in the global fit. We find that our approach yields a good description of the available Drell-Yan data, deep-inelastic scattering structure functions ($F_2$), and $J/\psi$ production across various energies and targets. The results provide significantly improved constraints on the gluon distributions at moderate and large $x$ in both the pion and the kaon, offering a more complete picture of their internal structure.

hep-ph↗
arXiv2026

Twisting Small-$x$ Gluon Tomography with Orbital Angular Momentum

We propose an orbital-angular-momentum-resolved extension of small-$x$ gluon tomography in hard diffractive dijet deep inelastic scattering. In the standard plane-wave setup, the elliptic correlation between the dijet relative momentum and the target recoil probes the elliptic component of the small-$x$ gluon Wigner distribution through a fixed transverse readout. We show that replacing the plane-wave lepton current by a twisted wave-packet current promotes this readout into a tunable OAM--Bessel projection kernel. The exchanged virtual photon is not treated as an asymptotic vortex particle; the OAM dependence enters through the transverse structure of the lepton electromagnetic current. The resulting observable is a family of $M$-resolved elliptic correlations $A_2^{(M)}(q_T,R_\gamma)$, where $q_T$ denotes the transverse Bessel scale of the projection kernel, not the transverse momentum of the exchanged photon. We derive the normalized linear response and show that it contains a subtraction from the deformation of the total diffractive rate. Consequently, the elliptic response can vanish while the diffractive rate remains finite. This finite-rate null is a normalized projection zero of the response to the target elliptic gluon component, not a disappearance of diffraction. It is not available as a tunable mode zero in the standard single plane-wave readout, and provides an external projection basis in which the response to the same small-$x$ elliptic geometry can be probed with either sign or tuned to zero.

hep-ph↗
arXiv2026

External-Field-Assisted Muon Reactivation in Muon-Catalyzed Fusion: A Rate-Network Criterion for Reducing Alpha Sticking

Alpha sticking is a major loss channel in deuterium--tritium muon-catalyzed fusion. We study whether an additional external-field-assisted stripping channel can reduce the residual sticking loss after conventional collisional reactivation. The external contribution is written as $R_X=f_XP_X\eta_X$, where $f_X$ is the space--time overlap between the external field and the residual stuck $(\alpha\mu)^+$ population, $P_X$ is the microscopic stripping probability, and $\eta_X$ is the probability that the stripped $\mu^-$ is returned to the $d\mu/t\mu\to dt\mu$ fusion cycle before escape or decay. This gives $\omega_S^{\rm eff}=\omega_S^0(1-R_{\rm col})(1-R_X)$ and leads directly to a probability-level no-go condition, $\eta_X^{\rm crit}>1$, for any target improvement requiring more recycling than is probabilistically available. We construct an energy-resolved post-stripping rate network including slowing down, atomic capture, free escape, muon decay, atomic-stage loss, ordinary molecular formation, and an effective resonant $dt\mu$ channel. Benchmark scans show that the useful regime is a transport window: the stripped muon must be confined and recycled efficiently. With the reference inputs used here, the best-performing scenario increases the cycle yield from $N_{\rm fus,\mu}=112.6$ in the collision-only case to $N_{\rm fus,\mu}=156.5$. Resonant molecular formation suppresses atomic-stage loss and broadens the high-recycling region, but it cannot compensate for prompt escape or poor field--population overlap. The rate network therefore identifies the transport and overlap conditions required for external-field-assisted reactivation to reduce residual alpha sticking.

nucl-th↗
arXiv2026

Muon-Catalyzed Nuclear Fusion: Physical Mechanism, Bottleneck Breakthroughs, and an Engineering Pathway

Muon-catalyzed nuclear fusion (\mucf) replaces atomic electrons with negative muons, compressing atomic orbitals by about two orders of magnitude and enabling deuterium--tritium (D--T) fusion under near-room-temperature conditions. This paper reviews the physical principles of \mucf{} and formulates its essential dynamics as a four-step cycle: muonic-atom formation, muon transfer, resonant \dtmu{} molecular formation, and D--T fusion with muon release and recycling. A kinetic model is used to quantify the number of catalysis cycles per muon and the corresponding energy gain. We focus on the central limitation of catalytic efficiency, namely the alpha-sticking effect, and discuss possible breakthrough routes including nuclear-spin and muon dual polarization, in-flight muon-catalyzed fusion, and heavy-ion-driven magneto-inertial fusion. Within the idealized assumptions of the present model, a four-dimensional synergistic scheme combining dual polarization, high-density confinement, electric-field-assisted muon recovery, and resonant enhancement may increase the number of catalysis cycles per muon from the present experimental record of about 150 to more than 500, potentially enabling an energy gain \(Q>2\). On this basis, we propose a conceptual fusion--fission fuel-breeding hybrid reactor, denoted as \mucf-FBR, which exploits the 14.1-MeV neutron yield of \mucf{} to breed \({}^{239}\mathrm{Pu}\) from a \({}^{238}\mathrm{U}\) blanket in a decoupled fusion--fission operating mode. This concept may offer advantages in engineering robustness, radiation-damage tolerance, and natural-uranium utilization.

hep-ph↗
arXiv2026

First mass determination of electroweak vortex rings in the Standard Model

We report the first rigorous evaluation of the physical mass of electroweak vortex rings, establishing precise values of 18.01 and 26.80 TeV for solutions characterized by different winding numbers. Analysis of the internal structure reveals that repulsive interactions shape the geometry of these configurations, while complex current distributions lead to a neutral analogue of Ampere's circuital law, suggesting a corresponding self-stabilizing pinch mechanism. These findings set the energy scales for the potential observation of such configurations at future colliders and offer a framework for understanding topological structures in the Standard Model.

hep-ph↗
arXiv2026

Probing Proton Structure via Physics-Guided Neural Networks in Holographic QCD

Describing the proton structure function $F_2$ in the non-perturbative and transition regimes of quantum chromodynamics (QCD) remains a significant theoretical challenge. In this work, we introduce a Physics-Guided Neural Network (PGNN) that integrates Holographic QCD with deep learning. By embedding the five-dimensional $\text{AdS}_5$ Dirac equation and the string diffusion kernel directly into the computational graph, the network is strictly constrained to the physical proton mass ($M_p \equiv 0.938 \text{ GeV}$). Applying this framework to high-precision SLAC deep inelastic scattering data yields a global fit of $\chi^2/\text{d.o.f.} \simeq 0.91$. Rather than relying on predetermined empirical forms, the network dynamically extracts the transition between the $s$-channel bulk fermion mechanism (hadronic resonance excitations) and the $t$-channel holographic Pomeron exchange (diffractive background), identifying a kinematic crossover near $x \approx 0.19$. Furthermore, the optimization naturally recovers a Pomeron intercept of $\alpha_0 \approx 1.0786$ and generates higher-twist scale-breaking effects through the evolution of resonance mass spectra. This demonstrates that embedding analytical differential equations into neural networks provides an interpretable, data-driven approach for phenomenological studies of strongly coupled systems.

hep-ph↗
arXiv2026

Probing a Fifth Force in Muonic Atoms through Lamb Shifts and Hyperfine Structure

Motivated by the ATOMKI anomalies in 8Be and 4He transitions, we study X17-induced Lamb shifts and hyperfine splittings in muonic atoms with stable nuclei up to Z <= 15. The bound-state problem is solved within the Gaussian Expansion Method using a unified Hamiltonian that includes the standard electromagnetic baseline together with vector and pseudoscalar X17 exchange. The spin-independent Lamb shift is described by a coherent vector muon-nucleus interaction, while the spin-dependent hyperfine sector is built isotope by isotope from shell-model spin fractions. We find a clear complementarity between mediator hypotheses: the vector Lamb-shift signal grows toward heavier nuclei, the vector hyperfine scenario favors odd-N nuclei, and the pseudoscalar scenario favors odd-Z nuclei. Using a signal-to-precision ratio, we identify muonic deuterium, muonic helium-3 ion, and muonic helium-4 ion as the most promising near-term Lamb-shift probes among systems with existing precision benchmarks. For future spectroscopy, the largest vector Lamb-shift signal is predicted in muonic silicon-29, while the leading 1S hyperfine targets are silicon-29 for the vector scenario and phosphorus-31 for the pseudoscalar scenario. The main theoretical uncertainty comes from the Schmidt-model treatment of nuclear spin content.

physics.atom-ph↗
arXiv2026

Extraction of the color dipole amplitude with physics-informed neural networks

The process-independence of the color dipole amplitude is a cornerstone of high-energy Quantum Chromodynamics (QCD). However, standard phenomenological approaches typically rely on rigid parametric ansatzes and often require ad-hoc geometric adjustments to reconcile inclusive and diffractive measurements. To resolve this tension, we introduce Physics-Informed Neural Networks (PINNs) employing a ``Teacher--Student'' strategy. The physics-based momentum-space Balitsky-Kovchegov evolution dynamics act as the ``Teacher,'' constraining the solution manifold, while the network ``Student'' is refined against inclusive HERA $F_2$ data. This approach extracts a model-independent dipole amplitude without assuming initial states. Strikingly, we demonstrate that this amplitude -- without parameter retuning or geometric rescaling -- successfully predicts the absolute normalization and kinematic dependence of exclusive $J/\psi$ photoproduction cross-sections. This parameter-free prediction of the saturation dynamics provides promising evidence for the process-independence of the gluon saturation scale and establishes PINNs as a transformative paradigm for uncovering non-perturbative QCD structures.

hep-ph↗
arXiv2025

Visible and Invisible Pseudoscalar Meson Decays from Anomaly Sum Rules

The decays of pseudoscalar mesons to real and virtual photons as well as neutrino-antineutrino pairs are considered in the framework of the dispersive method based on Anomaly Sum Rules. The contribution of singlet channel involving the new non-perturbative gluon form factor of virtual photon $B(q^2)$ is systematically taken into account. The detailed analysis of its dependence on photon virtuality $q^2$ relying on the available data for meson transition fomfactors is performed. It is shown that B has quite a nontrivial structure at $q^2 \sim 1 GeV^2$ which may be a signal of the existence of pseudoscalar glueball with a mass about 1.5-2 GeV. The calculation of the decay to $\nu \bar \nu$ pairs leads to the compatibility with the result of Arnellos, Marciano and Parsa of 1982, when pion decay is considered neglecting the mixing effects. The account for these effects results, however, in the enhancement of pion branching ratio by a factor of 3, while that for eta decay is larger by several orders of magnitude. It is stressed, that dependence on the pair invariant mass is entirely defined by QCD and coincides with that of the meson transition form factor. The role of obtained results for the physics at HHaS detector at HIAF is discussed.

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

Probing Saturon-like Limits in QCD Systems

High-occupancy QCD matter enters a saturated regime when its entropy or occupancy approaches the unitarity bound $\sim 1/\alpha$, the ``saturon" criterion. We test this criterion for protons and nuclei at small $x$ using analytic and numerical solutions of the BK equation. From these solutions we construct the gluon occupancy $N_g(x)$ and a thermodynamic entropy $S(x)$ via an Unruh-like temperature $T = Q_s/(2\pi)$ and an emergent gluon mass $M_g \sim Q_s$. For protons, both $N_g$ and $S$ rise toward small $x$ yet stay below $1/\alpha_s$ in our baseline setup. For nuclei, by contrast, the nuclear entropy $S_A$ attains the $1/\alpha_s$ benchmark in a small-$x$ window where the proton does not. This singles out nuclei as the natural environment to search for saturon-like behavior and motivates precision small-$x$ measurements and high-occupancy $pA$ and $AA$ collisions.

hep-ph↗
arXiv2025

Gluon Condensation as a Unifying Mechanism for Special Spectra of Cosmic Gamma Rays and Low-Momentum Pion Enhancement at the Large Hadron Collider

Decoding the internal structure of the proton is a fundamental challenge in physics. Historically, any new discovery about the proton has fuelled advances in several scientific fields. We have reported that gluons inside the proton accumulate near the critical momentum due to chaotic phenomena, forming gluon condensation. Surprisingly, the pion distribution predicted by this gluon distribution for the production of high-energy proton collisions could answer two puzzles in astronomy and high-energy physics. We find that during ultrahigh-energy cosmic ray collisions, gluon condensation may abruptly produce a large number of low-momentum pions, whose electromagnetic decays have the typical breakout properties appearing in various cosmic gamma-ray spectra. On the other hand, the Large Hadron Collider (LHC), which is well below the cosmic ray energy scale, also shows weak but recognisable signs of gluon condensation, which had been mistaken for BEC pions. The connection between these two phenomena, which occur at different scales in the Universe, supports the existence of a new structure within the proton-gluon condensation.

hep-ph↗
arXiv2025

Criterion for the Existence of the $G(3900)$ Resonance

About 18 years ago, the BABAR and the Belle Collaborations reported evidence for a new $c\bar{c}$ structure near $3900~\mathrm{MeV}$ in $e^{+}e^{-} \to D\bar{D}$, triggering debate over whether it represents a genuine hadronic state or arises from interference effects and the opening of the $D^{*}\bar{D}$ threshold. The issue remained unsettled until 2024, when BESIII, with an enlarged $e^{+}e^{-} \to D\bar{D}$ sample, confirmed the presence of the $G(3900)$ structure, reviving discussion of its nature. Although it has been proposed as a $P$-wave $D\bar{D}^{*}$ molecular state, no consensus has emerged, and interference effects remain a plausible explanation. In this Letter, we show that analyzing the $e^{+}e^{-}\to D\bar{D}$ cross section as a function of the transverse momentum of the final-state $D$ meson reveals a prominent Jacobian peak. This feature cannot be generated by interference effects alone and thus provides direct evidence for the existence of $G(3900)$. Moreover, the peak position is highly sensitive to the actual mass of $G(3900)$, offering a precise determination method. The criterion illustrated by $G(3900)$ can be extended to other hadronic systems, offering a powerful tool to identify genuine resonances.

hep-ph↗
arXiv2025

Emergence of Photon Bose-Einstein Condensation from Down-Scattering in Cold Electron Media

In this study, we examine the emergence of photon Bose-Einstein condensation (BEC) resulting from the interaction of high-energy photons with a cold electron gas, modeled via a modified Kompaneets equation. Beginning with an initial black-body photon spectrum, we perform numerical simulations to track the evolution of the photon distribution under the influence of inverse Compton scattering, wherein photons dissipate energy through collisions with cold electrons. Our results demonstrate a pronounced enhancement of photon number density at the low-energy tail, indicative of a BEC-like phase transition. This phenomenon is further corroborated by an analysis of the entropy evolution during the cooling process, revealing that the condensate configuration corresponds to the entropy maximum, in accordance with thermodynamic principles. These findings establish a comprehensive theoretical framework for photon BEC formation in cold electron environments and underscore the significance of entropy maximization as a driving mechanism for condensation.

hep-ph↗
arXiv2025

Transport Properties of QGP within a Bayesian Holographic QCD Model

Using a holographic QCD model augmented by Bayesian inference, we calculate key transport coefficients of the quark-gluon plasma (QGP)$\text{-}$including the drag force, jet quenching parameter, heavy quark diffusion coefficient, and shear and bulk viscosities$\text{-}$at finite temperature and chemical potential. Posterior parameter distributions at the 68\% and 95\% confidence levels (CL), as well as the maximum a posteriori (MAP) estimates, are employed to quantify uncertainties. Our findings indicate that the diffusion coefficient within the Bayesian credible regions aligns with lattice QCD results for $T \sim 1.2T_c$ to $2T_c$, and is consistent with ALICE experimental measurements near $T_c$. The jet quenching parameter obtained from the Bayesian analysis agrees with RHIC and LHC data, while viscosity coefficients show compatibility with existing literature. These results demonstrate the efficacy of a Bayesian holographic approach in elucidating the nonperturbative transport properties of QCD matter.

hep-ph↗
arXiv2025

Topological Stabilization via Higgs and $Z$-Boson Mediated Repulsions in Electroweak Monopole-Antimonopole Pairs

We identify two distinct repulsive mechanisms in the Cho-Maison monopole-antimonopole pair (MAP) configuration. Our results show that the Higgs-mediated repulsion exhibits a non-monotonic dependence on both topological charge and Higgs self-coupling, confirming its topological origin while revealing a mass-controlled range transition that deviates from the exponential form of a Yukawa potential. Simultaneously, the $Z$-boson field generates localized repulsive cores of radius $R_c\approx0.8\,m_W^{-1}$, consistent with the weak interaction scale. The collaborative effect of these mechanisms -- operating in different physics regimes -- counteracts the magnetic attraction, establishing a stabilization paradigm for the Cho-Maison MAP that extends naturally to other topological solitons in the Standard Model and various systems described by effective field theories.

hep-ph↗