arXiv subjects

Fuqiang Wang

Publications and source records attributed to Fuqiang Wang.

At least 19 recordsLinked to original sources

arXiv2026

PaperFlow: Profiling, Recommending, and Adapting Across Daily Paper Streams

Scientific paper recommendation is typically evaluated as static ranking over a fixed candidate set, yet real scientific reading unfolds as a daily, longitudinal process in which interests shift and feedback accumulates. We introduce PaperFlow, a framework that organizes it into three coupled stages: Profiling, which constructs and maintains a structured, inspectable scholarly profile from heterogeneous cold-start evidence; Recommending, which ranks each date-specific paper stream through multi-signal aggregation under a fixed display budget; and Adapting, which updates user state from semantically distinct feedback signals and models interest drift across days. We further define a longitudinal user-day benchmark that fixes users, dates, candidate pools, visible inputs, and hidden simulated relevance labels under a shared temporal information boundary. The benchmark contains 24 simulated research users, 50 daily paper streams, 1,200 user-day episodes, 20,727 unique papers, and 497,448 episode-paper records. We additionally specify a blind human-evaluation protocol to validate alignment between automatic metrics and expert judgments. Experiments against five scientific recommendation baselines show that PaperFlow achieves the strongest oracle-based ranking, the highest behavioral alignment with simulated reading selections, and the best blind human-evaluation score.

cs.IR↗

arXiv2026

A higher-harmonic observable for the chiral magnetic effect in heavy-ion collisions

The chiral magnetic effect (CME) is a phenomenon in which electric charge is separated by a strong magnetic field from local domains of chirality imbalance in quantum chromodynamics. The CME-sensitive azimuthal correlator difference $\Delta\gamma$ between opposite- and same-sign charged hadron pairs is designed to detect charge separation along the magnetic field, on average perpendicular to the reaction plane. However, the search for the CME is hindered by large background contributions to $\Delta\gamma$ from particle correlations coupled with elliptic flow. In this work, we explore higher-harmonic components in differential $\Delta\gamma(\phi_{\rm pair})$ as a function of the pair azimuthal angle. Such components could arise from event-by-event fluctuations of the magnetic fields throughout the collision zone, in both direction and magnitude. We show by using heavy-ion physics models that the hexadecapole component of $\Delta\gamma(\phi_{\rm pair})$ is sensitive to the CME and insensitive to physics backgrounds. This could offer a unique observable for the CME that is robust against background contributions.

nucl-th↗

arXiv2025

Experimental review on the chiral magnetic effect in relativistic heavy ion collisions

The chiral magnetic effect (CME) refers to a predicted phenomena in quantum chromodynamics that manifests as a charge separation along an external magnetic field, driven by an imbalance of quark chirality. Searches for the CME has been carried out by azimuthal particle correlations in relativistic heavy ion collisions where such a chirality imbalance is anticipated and a strong magnetic field is created in the initial stage. No conclusive experimental evidence on the CME has been established so far because of large background contributions to azimuthal correlation observables. We review the status of the experimental search for the CME, covering the observables used, the techniques to mitigate backgrounds, and the strengths and limitations of various experimental approaches, and outline a future prospect of the CME search in high-energy nuclear collisions.

nucl-ex↗

arXiv2025

Investigating the Event-Shape Methods in Search for the Chiral Magnetic Effect in Relativistic heavy-ion Collisions

The azimuthal correlator $\Delta\gamma$ searching for the chiral magnetic effect (CME) is contaminated by a major background proportional to the elliptic flow $v_2$. Event-shape engineering (ESE) and event-shape selection (ESS) binning events in {\em dynamical} and {\em statistical} fluctuations of $v_2$, respectively, are two methods searching for the CME. We conduct a systematic study using physics and toy model simulations. It is found that ESE fulfills the general premise of measuring the CME but is statistically hungry, whereas ESS is not practical to measure the CME because of the intertwining variables used in the method.

nucl-ex↗

arXiv2025

Exploring Data-Driven Corrections for $\phi$-Meson Global Spin Alignment Measurements

Non-central heavy ion collisions generate large orbital angular momentum (OAM), providing opportunities to study spin phenomena such as the global spin alignment of vector mesons. Such studies are expected to reveal properties of the quark-gluon plasma produced in these collisions. Global spin alignment of vector mesons, such as the $\phi$-meson, can be measured by the $00^{\rm th}$ coefficient of the spin density matrix, $\rho_{00}$, via the polar angle of the decay kaon momentum in the parent rest frame with respect to the OAM direction of the collision. A deviation of $\rho_{00}$ from the isotropic value of $1/3$ indicates a finite spin alignment. The reported signal of $\rho_{00}-1/3$ is on the order of $\sim 1\%$ and therefore corrections for finite detector performance and acceptance, which are expected to be on the order of a few tenths of a percent, are important. Additional complications in the detector corrections may arise from the $\phi$-meson azimuthal anisotropy which could become intertwined with the detector efficiency. Typically, detector corrections for global spin alignment of vector mesons are performed with Monte-Carlo (MC) methods using detector simulation packages such as GEANT, however it is unclear if such methods can be trusted at the needed level of precision. In this paper, we investigate an alternative, data-driven approach in correcting for detector effects. This approach utilizes detector effects on combinatorial kaon pairs from $\phi$-meson decays that fall within the $\phi$-meson mass window, which can be obtained through statistical identification of decay kaons in real data analysis. We examine the degree of success of such a data-driven approach using toy-model MC simulations as well as its shortcomings.

nucl-ex↗

arXiv2025

Energy-Embedded Neural Solvers for One-Dimensional Quantum Systems

Physics-informed neural networks (PINN) have been widely used in computational physics to solve partial differential equations (PDEs). In this study, we propose an energy-embedding-based physics-informed neural network method for solving the one-dimensional time-independent Schr\"{o}dinger equation to obtain ground- and excited-state wave functions, as well as energy eigenvalues by incorporating an embedding layer to generate process-driven data. The method demonstrates high accuracy for several well-known potentials, such as the infinite potential well, harmonic oscillator potential, Woods-Saxon potential, and double-well potential. Further validation shows that the method also performs well in solving the radial Coulomb potential equation, showcasing its adaptability and extensibility. The proposed approach can be extended to solve other partial differential equations beyond the Schr\"{o}dinger equation and holds promise for applications in high-dimensional quantum systems.

physics.comp-ph↗

arXiv2025

A "breathing'' octupole $^{208}$Pb nucleus: resolving the elliptical-to-triangular azimuthal anisotropy puzzle in ultracentral relativistic heavy ion collisions

Relativistic heavy ion collisions provide a unique opportunity to probe the nuclear structure by taking an instantaneous snapshot of the colliding nuclei and converting it into momentum anisotropies of final emitted hadrons. A long-standing puzzle of too large a ratio of the elliptical-to-triangular ($v_{2}$-to-$v_{3}$) anisotropies in ultracentral $^{208}$Pb+$^{208}$Pb collisions at the Large Hadron Collider(LHC) cannot be solved simply by hydrodynamic simulations with initial conditions containing the spherical or certain deformed shape of $^{208}$Pb. In this Letter, using the iEBE-VISHNU relativistic viscous hydrodynamic hybrid model simulations with the Trento initial condition, we show that a dynamic octupole deformation--a shape-breathing of $^{208}$Pb --could potentially solve the $v_{2}$-to-$v_{3}$ puzzle and simultaneously describe the $v_3\{4\}$ data measured in experiment. Our results highlight the unique capability of capturing transient collective properties of nuclei on yoctosecond ($10^{-24}$~s) timescales, unfeasible with low-energy nuclear reactions.

nucl-th↗

arXiv2025

Experimental Search for the Chiral Magnetic Effect in Relativistic Heavy-Ion Collisions: A Perspective

The chiral magnetic effect (CME) refers to generation of the electric current along a magnetic field in a chirally imbalanced system of quarks. The latter is predicted by quantum chromodynamics to arise from quark interaction with non-trivial topological fluctuations of the vacuum gluonic field. The CME has been actively searched for in relativistic heavy-ion collisions, where such gluonic field fluctuations and a strong magnetic field are believed to be present. The CME-sensitive observables are unfortunately subject to a possibly large non-CME background, and firm conclusions on a CME observation have not yet been reached. In this perspective, we review the experimental status and progress in the CME search, from the initial measurements more than a decade ago, to the dedicated program of isobar collisions in 2018 and the release of the isobar blind analysis result in 2022, to intriguing hints of a possible CME signal in Au+Au collisions, and discuss future prospects of a potential CME discovery in the anticipated high-statistic Au+Au collision data at the Relativistic Heavy-Ion Collider by 2025. We hope such a perspective will help sharpening our focus on the fundamental physics of the CME and steer its experimental search.

nucl-ex↗

arXiv2025

Impact of Tracking Resolutions on $\phi$-Meson Spin Alignment Measurement

Measurements of global spin alignment of vector mesons in relativistic heavy-ion collisions can provide unique insights into spin-orbit interactions and vector meson dynamics in the Quark-Gluon Plasma (QGP) produced in those collisions. The global spin alignment is measured by the $00^{\rm th}$ coefficient of the spin density matrix, $\rho_{00}$, via the polar angle ($\theta^{*}$) of the decay-daughter momentum in the parent rest frame with respect to the direction of the orbital angular momentum of the collision. Such measurements are affected by the angular and momentum resolutions of the reconstructed tracks in the experiment. Such effects are nontrivial because of kinematic complications caused by the boost to the parent rest frame, and could be important given that the global spin alignment signal is weak. In this paper, we investigate the effects of experimental tracking resolutions on measurements of the $\phi$(1020) meson $\rho_{00}$. We study these effects for two methods of $\rho_{00}$ measurements, the conventional method analyzing the $\phi$-meson yield versus $\cos^2 \theta^*$ and the invariant mass ($m_{\rm inv}$) method utilizing $\langle\cos^2\theta^*\rangle$ versus $m_{\rm inv}$. Using typical resolution values from experiments, we find that the effect of track resolution on $\rho_{00}$ is small, well within typical measurement uncertainties.

physics.data-an↗

arXiv2024

Azimuthal Correlation Anisotropies in p + p Collisions Simulated by Pythia

Stimulated by the keen interest of possible collective behavior in high-energy proton-proton and proton-nucleus collisions, we study two-particle angular correlations in pseudorapidity and azimuthal differences in simulated p + p interactions by the Pythia 8 event generator. Multi-parton interactions and color connection are included in these simulations which have been perceived to produce collectivity in final-state particles. Meanwhile, contributions from genuine few-body nonflow correlations, not of collective flow behavior, are known to be severe in those small-system collisions. We present our Pythia correlation studies in a pedagogical way and report azimuthal harmonic anisotropies analyzed by several methods. We observe anisotropies in those Pythia simulated events qualitatively and semi-quantitatively similar to experimental data. Our findings highlight the delicate nature of azimuthal anisotropies in small-system collisions, and provide a benchmark helping improve data analysis and interpret experimental measurements in small-system collisions.

nucl-th↗

arXiv2024

Radiative cooling capacity on Earth

By passively dissipating thermal emission into the ultracold deep space, radiative cooling (RC) is an environment-friendly means for gaining cooling capacity, paving a bright future for global energy saving and carbon dioxide reduction. However, assessing the global RC capacity at the day-to-annual scale remains challenging as the RC capacity significantly depends on geographic and environmental conditions. To our knowledge, no analysis of global RC capacity has been reported. Herein, we show the distribution of RC capacity on Earth by establishing a precise assessment model for evaluating the performance of a radiative cooler. Our assessment is comprehensively validated against experimental data and extended to elucidate the capacity of representative broadband and selective cooler. We also categorize the global RC capacity into five representative regions based on the year-round cooling power. Our assessment can inform trade-offs between design and practical application for the RC systems, alongside promoting RC-based technologies to tackle worldwide energy and environment challenges.

physics.app-ph↗

arXiv2024

Investigating event-shape methods in the search for the chiral magnetic effect in relativistic heavy ion collisions

The Chiral Magnetic Effect (CME) is a phenomenon in which electric charge is separated by a strong magnetic field from local domains of chirality imbalance and parity violation in quantum chromodynamics (QCD). The CME-sensitive observable, charge-dependent three-point azimuthal correlator $\Delta\gamma$, is contaminated by a major physics background proportional to the particle's elliptic flow anisotropy $v_2$. Event-shape engineering (ESE) binning events in dynamical fluctuations of $v_2$ and event-shape selection (ESS) binning events in statistical fluctuations of $v_2$ are two methods to search for the CME by projecting $\Delta\gamma$ to the measured anisotropy $v_2=0$ intercept. We conduct a systematic study of these two methods using physics models as well as toy model simulations. It is observed that the ESE method fulfills the general premise of measuring the CME but is statistically hungry. It is found that the intercept from the ESS method depends on the details of the event content, such as the mixtures of background-contributing sources, because of statistical fluctuations of intertwining variables used in the method, and is thus not practically useful or clean to measure the CME.

physics.data-an↗

arXiv2024

Review of nonflow estimation methods and uncertainties in relativistic heavy-ion collisions

Collective anisotropic flow, where particles are correlated over the entire event, is a prominent phenomenon in relativistic heavy-ion collisions and is sensitive to the properties of the matter created in those collisions. It is often measured by two- and multi-particle correlations and is therefore contaminated by nonflow, those genuine few-body correlations unrelated to the global event-wise correlations. Many methods have been devised to estimate nonflow contamination with various degrees of successes and difficulties. Here, we review those methods pedagogically, discussing the pros and cons of each method, and give examples of ballpark estimate of nonflow contamination and associated uncertainties in relativistic heavy-ion collisions. We hope such a review of the various nonflow estimation methods in a single place would prove helpful to future researches.

nucl-ex↗

arXiv2024

Properties of the QCD Matter -- An Experimental Review of Selected Results from RHIC BES Program

In the paper, we discuss the development of the multi-gap resistive plate chamber Time-of-Flight (TOF) technology and the production of the STAR TOF detector in China at the beginning of the 21st century. Then we review recent experimental results from the first beam energy scan program (BES-I) at the Relativistic Heavy Ion Collider (RHIC). Topics cover measurements of collectivity, chirality, criticality, global polarization, strangeness, heavy-flavor, di-lepton and light nuclei productions.

nucl-ex↗

arXiv2024

Observation of Universal Expansion Anisotropy from Cold Atoms to Hot Quark-Gluon Plasma

Azimuthal anisotropy has been ubiquitously observed in high-energy proton-proton, proton-nucleus, and nucleus-nucleus (heavy-ion) collisions, shaking the early belief that those anisotropies require an intense phase of multiple interactions between the created particles. This work reports a study of anisotropic expansion of cold $^{6}$Li Fermi gases, initially trapped in an anisotropic potential, as a function of the interaction strength that can be readily tuned by an external magnetic field. It is found that the expansion anisotropy builds up quickly at small interaction strength, without the need of a large amount of interactions. An unexpected and quantitative universal scaling of the expansion anisotropy is observed for the first time between cold atom and heavy-ion systems as a function of the number of collisions per particle or opacity ($n_{\rm coll}$), despite their vast differences in scale and physics. The expansion isotropy in both the cold atom gases and heavy-ion collisions increases smoothly and shows no sign of saturation in the observed opacity range, with an approximate power-law dependence of $\sqrt{n_{\rm coll}}$, characteristic of random walks. This universality potentially unifies a variety of vastly different physical systems, from weakly interacting dilute gases to the strongly interacting quark-gluon plasma of the early universe.

cond-mat.quant-gas↗

arXiv2024

Influence of the chiral magnetic effect on particle-pair elliptic anisotropy

Chiral Magnetic Effect (CME) is a phenomenon in which electric charge is separated by a strong magnetic field from local domains of chirality imbalance in quantum chromodynamics. The CME-sensitive, azimuthal correlator difference $\Delta\gamma$ between opposite-sign (OS) and same-sign (SS) charged hadron pairs is contaminated by a major physics background proportional to the particle elliptic anisotropy ($v_2$). The CME signal, on the other hand, contributes to the difference in the pair elliptic anisotropies between OS and SS pairs ($\Delta v_{2,\rm pair}$). We investigate $\Delta v_{2,\rm pair}$ and found its sensitivity to CME to be similar to that of the $\Delta\gamma$ observable.

hep-ph↗

arXiv2024

Hexadecapole deformation of $^{238}$U from relativistic heavy-ion collisions using a nonlinear response coefficient

The hexadecapole deformation ($\beta_4$) of the $^{238}$U nucleus has not been determined because its effect is overwhelmed by those from the nucleus' large quadrupole deformation ($\beta_2$) in nuclear electric transition measurements. In this Letter, we identify the nonlinear response of the hexadecapole anisotropy to ellipticity in relativistic $^{238}$U+ $^{238}$U collisions that is solely sensitive to $\beta_4$ and insensitive to $\beta_2$. We demonstrate this by state-of-the-art hydrodynamic calculations and discuss the prospects of discovering the $\beta_4$ of $^{238}$U in heavy-ion data at the Relativistic Heavy Ion Collider.

nucl-th↗

arXiv2024

The nonflow issue in connecting anisotropy measurements to hydrodynamics in relativistic heavy-ion collisions

Hydrodynamics can describe majority of the measured azimuthal anisotropies in relativistic heavy-ion collisions. Many of the anisotropy measurements are contaminated by nonflow correlations (i.e., those unrelated to global event-wise correlations). Those nonflow contamination can cause incorrectness or compromise the accuracy of the physics extracted from data-hydrodynamics comparison, particularly when one relies on subtle difference in the measurements. In the recent preprint by STAR (arXiv:2401.06625) extracting the Uranium nucleus deformation parameter, nonflow contamination is assessed by subevents in the limited STAR acceptance. In this note, we demonstrate that such assessment is inadequate and illustrate how large an effect nonflow can cause by using the HIJING model, in which all correlations are nonflow and non-hydrodynamic. We thereby conclude that the extracted Uranium deformation parameter is premature and emphasize the importance of an earnest assessment of or correction for nonflow contamination, not only for this STAR analysis but more generally for studies relying on comparing anisotropy measurements to hydrodynamic calculations.

nucl-ex↗