arXiv subjects

Zebo Tang

Publications and source records attributed to Zebo Tang.

At least 19 recordsLinked to original sources

arXiv2026

Time performance of USTC-IME LGAD under synchrotron light source focused X-ray

The time performance of Low Gain Avalanche Diodes (LGADs), designed by the University of Science and Technology of China (USTC) and fabricated by the Institute of Microelectronics of Chinese Academy of Sciences (IME), was characterized at the Shanghai Synchrotron Radiation Facility (SSRF). The experiment was conducted at the BL16B1 beamline, which delivers a focused X-ray beam with a diameter of 500 {\mu}m, a repetition period of 2 ns, and a photon energy of 10 keV. Using a fast oscilloscope, waveforms containing continuous signal pulses were recorded within a 50 ns time window. The LGAD under test successfully resolved the 2 ns period of the SSRF. To mitigate pile-up effects and extract pulse-by-pulse information from the acquired waveforms, a waveform-level global template fitting method was employed. The time resolution was then estimated using a combined profile likelihood approach, yielding a value of 126.6 ps. The effect of random photon absorption depth on the time resolution of LGADs was studied through dedicated simulations.

physics.ins-det↗

arXiv2026

Development of Small-pitch, Ultra-thin 3D Silicon Sensors at USTC

We report on the development of 3D silicon sensors at the University of Science and Technology of China (USTC). The sensor involves columnar electrodes (5 um in diameter) of both doping types, etched from the same wafer side. The p+ electrodes pass through the epitaxial wafer, whereas the n+ electrodes stop at a short distance from the opposite side of the epitaxial wafer. With respect to previous generations of 3D sensors, they feature an ultra-thin active substrate (50 um) and a small pixel size of 50 um x 50 um or 25 um x 25 um. This R&D project aims to establish a sensor technology to simultaneously measure position and time information at the single-pixel level. The first run with one merged wafer layout has been completed. The design, fabrication, and characterization of the sensors are reported in this paper.

physics.ins-det↗

arXiv2026

Measure charge transport in high-energy nuclear collisions with an energy scan of isobaric collisions

We present a method to measure electric-charge transport in high-energy nuclear collisions using a beam-energy scan of isobaric systems. Comparing collisions of nuclei with identical mass number but different atomic number allows the charge difference ($\Delta Q$) to be extracted with a double-ratio technique that suppresses most experimental systematic uncertainties. By varying the beam energy, the rapidity gap ($\Delta y$) over which electric charge is transported can be systematically scanned. Simulations of Ru+Ru and Zr+Zr collisions at $\sqrt{s_{\rm NN}}$=19.6-200GeV with UrQMD and PYTHIA Angantyr show that midrapidity $\Delta Q$ decreases exponentially with increasing $\Delta y$, with the slope parameter exhibiting strong model dependence. Comparisons with the baryon number transport reveal distinct patterns. In both UrQMD and PYTHIA Angantyr (with and without final-state baryon junctions), where baryon number is carried solely by valence quarks, the rapidity slope for baryon transport is larger than that for electric-charge transport. In contrast, scenarios that include baryon junctions in the initial state are expected to produce the opposite trend. This demonstrates that an isobar beam-energy scan provides a sensitive probe of electric-charge transport and offers new constraints on the microscopic mechanisms governing conserved-charge redistribution in QCD matter.

nucl-ex↗

arXiv2026

Production of muonic kaon atoms at high-energy colliders

We develop a framework for the formation of exotic muonic kaon atoms ($K\mu$) in semileptonic $D^{0}$ decays, using the effective weak Hamiltonian, a helicity-based treatment of the leptonic current, and a nonrelativistic bound-state projection. The resulting branching ratio, $\mathrm{BR}(D^{0} \to (K\mu )\nu_{\mu})=2.29\times10^{-10}$, is implemented in a ROOT-based code to estimate yields at RHIC, LHC, and STCF. We show quantitatively that $K\mu$ atoms-also produced through coalescence in the quark-gluon plasma (QGP)-provide a sensitive probe of low-momentum primordial muons and early time electromagnetic radiation, offering complementary constraints in an otherwise unexplored phase space for thermal dilepton and photon emission. Newly estimated dissociation cross sections in detector material indicate that secondary-vertex reconstruction should be experimentally feasible, allowing clean experimental identification of the atoms. Projected yields from QGP coalescence in LHC and RHIC heavy-ion collisions, and from $D^{0}$ decays in LHC high luminosity $p+p$ collisions indicate that the first observation of $K\mu$ atoms is within reach.

hep-ph↗

arXiv2026

Interference-induced entanglement in an effectively zero-lifetime particle pair

Quantum entanglement in high-energy collisions is often obscured by finite lifetimes, dynamical evolution, and final-state interactions, complicating the identification of genuinely quantum correlations. Ultra-peripheral heavy-ion collisions provide a clean benchmark via the Drell-S${\rm\ddot{o}ding}$ production of nonresonant pion pair, realizing an effectively zero-lifetime particle pair whose quantum correlations are fixed at production and remain robust against subsequent elastic scattering. The coherent superposition of photoproduction amplitudes from two indistinguishable nuclei encodes the linear polarization of quasi-real photons in the orbital motion of the pair, generating a nonfactorizable two-particle quantum state. This entanglement leaves a direct experimental imprint: a characteristic second-harmonic azimuthal modulation in momentum space arising from spin-dependent interference between the two sources. In this paper, we establish a quantitative framework for Drell-S${\rm\ddot{o}ding}$ pion-pair production in relativistic heavy-ion collisions and predict the magnitude and transverse-momentum dependence of the entanglement-induced azimuthal asymmetry. Our results provide experimentally accessible signatures of interference-induced entanglement and a controlled test of quantum coherence in relativistic environments.

hep-ph↗

arXiv2026

Selected highlights from STAR experiment

In this paper, we review recent highlights in heavy-ion collisions and proton-proton collisions at top energies from STAR experiment at the Relativistic Heavy Ion Collider (RHIC) with key contributions from Chinese groups, including the Quark-Gluon Plasma (QGP) bulk properties, electromagnetic probes, heavy flavor and jets, antimatter hyper-nucleus, nuclear structure, global polarization, and nucleon spin structure. These data serve as important ingredients in the physics of Quantum Chromodynamics (QCD).

nucl-ex↗

arXiv2025

A muon scattering tomography system based on high spatial resolution scintillating detector

Cosmic ray muon scattering tomography (MST) is an imaging technique that utilizes muon scattering in matter to inspect high-Z materials non-destructively, without requiring an artificial radiation source. This method offers significant potential for applications in border security and long-term monitoring of nuclear materials. In this study, we developed a high-precision plastic-scintillator-based position-sensitive detector with a spatial resolution of 0.09 times the strip pitch. A fully functional, full-scale imaging system was then constructed using four layers of such XY position-sensitive detectors, each with an effective area of 53 cm x 53 cm. This paper details the following key contributions: the Geant4-simulated design and optimization of the imaging system, the fabrication, assembly, and testing of the detectors, and an evaluation of the imaging performance of the completed system.

physics.ins-det↗

arXiv2025

Reducing Systematic Bias in Machine Learning Applications to Signal Extraction in High-Energy Nuclear Physics

Machine learning techniques are increasingly being applied in high-energy nuclear physics data analysis thanks to their outstanding performance. One key challenge in such applications is the construction of training samples that can accurately represent real data. Training samples are typically generated through detector simulations, but discrepancies between simulated and real data can lead to degradation in machine learning performance and systematic biases in the results. This paper introduces two methods: i) cumulative distribution function mapping and ii) shift-and-scale, to align simulated signals with real data, which can aid in eliminating the aforementioned issues. We use the J/$\psi$ yield measurement in 200 GeV Ru+Ru and Zr+Zr collisions with the STAR experiment as an example to demonstrate the application and effectiveness of the proposed methods.

nucl-ex↗

arXiv2025

Energy dependence of rescattering effect on vector mesons spin alignment at RHIC

Spin alignment of vector mesons in heavy-ion collisions provides a novel probe of quark polarization and hadronization mechanism in quark-gluon plasma. Hadronic rescattering may affect the measured spin alignment of vector mesons due to non-uniform rescattering probability in non-central heavy-ion collisions. Using the UrQMD model, we systematically investigated the hadronic rescattering effect on the measurement of $\rho_{00}$, the spin alignment parameter, for $K^{*0}$, $\phi$, and $\rho^{0}$ mesons in Au+Au collisions at $\sqrt{s_\mathrm{NN}}$ = 7.7 - 200 GeV. Our results reveal that the measurable $\rho_{00} - 1/3$ remains unaffected for $\phi$, while shows significantly negative (positive) deviations for $K^{*0}$ and $\rho^0$ with respect to the reaction (production) plane. Quantitatively, the maximum deviation reaches $-0.0056$ ($0.0268$) for $K^{*0}$ and $-0.0122$ ($0.0414$) for $\rho^{0}$ with respect to the reaction (production) plane. Notably, the deviations in $\rho_{00}$ for both $K^{*0}$ and $\rho^{0}$ increase monotonically with increasing collision energy. These findings underscore the critical necessity of accounting for rescattering effects when interpreting spin alignment measurements of short-lived vector mesons in heavy-ion collisions.

nucl-ex↗

arXiv2025

Probing the Collision Geometry via Two-Photon Processes in Heavy-Ion Collisions

The initial collision geometry, including the reaction plane, is crucial for interpreting collective phenomena in relativistic heavy-ion collisions, yet it remains experimentally inaccessible through conventional measurements. Recent studies propose utilizing photon-induced processes as a direct probe, leveraging the complete linear polarization of emitted photons whose orientation strongly correlates with the collision geometry. In this work, we employ a QED-based approach to systematically investigate dilepton production via two-photon processes in heavy-ion collisions at RHIC and LHC energies and detector acceptances. Our calculations reveal that dilepton emission exhibits significant sensitivity to the initial collision geometry through both the azimuthal angles of their emission (defined by the relative momentum vector of the two leptons) and the overall momentum orientation of the dilepton pairs. These findings highlight the potential of two-photon-generated dileptons as a novel, polarization-driven probe to quantify the initial collision geometry and reduce uncertainties in characterizing quark-gluon plasma properties.

hep-ph↗

arXiv2025

Calculations of Di-Hadron Production via Two-Photon Processes in Relativistic Heavy-Ion Collisions

Two-photon processes in relativistic heavy-ion collisions have emerged as a critical probe of quantum electrodynamics in ultra-intense electromagnetic fields, with recent focus extending beyond dileptons to hadronic final states. At present, quantitative studies of di-hadron production via two-photon interactions remain scarce. In this work, we employ the Equivalent Photon Approximation and the two-photon fusion measurements from $e^{+}e^{-}$ collisions to obtain differential cross-section predictions for $\pi^{+}\pi^{-}$, $K^{+}K^{-}$, and $p\bar{p}$ pairs produced in ultra-peripheral $\mathrm{Au{+}Au}$ collisions at $\sqrt{s_{NN}} = 200\,\text{GeV}$ within the STAR acceptance, as well as in $\mathrm{Pb{+}Pb}$ collisions at $\sqrt{s_{NN}} = 5.36\,\text{TeV}$ within typical LHC acceptance. The calculations deliver the unified baseline for light-meson and baryon pairs in this environment, supplying benchmarks for upcoming STAR and LHC measurements and guiding future systematic investigations of hadronic two-photon processes at RHIC and LHC facilities.

hep-ph↗

arXiv2025

Influence of the residual magnetic field on the azimuthal distribution of final-state particles in photon-nuclear processes

In relativistic heavy-ion collisions, charged particles are accelerated to nearly the speed of light, and their external electromagnetic fields can be effectively approximated as quasi-real photons. These photons interact with another nucleus via photon-nuclear interactions, producing vector mesons. These vector mesons possess extremely low transverse momentum (pT ~ 0.1 GeV/c), distinguishing them from particles produced via hadronic interactions. STAR and ALICE have observed J/psi, rho0 and other vector mesons with very low pT, which are well described by photoproduction models. This unique characteristic of having extremely low transverse momentum allows them to serve as a novel experimental probe. Recent STAR results show that the equivalent photons in photoproduction processes are fully linearly polarized, affecting the azimuthal distribution of final-state particles like rho0 -> pi+ pi-. Since the polarization links to the initial collision geometry, the rho0 azimuthal modulation can probe nuclear structure. However, the post-collision magnetic field may deflect these particles, distorting the azimuthal distribution and complicating structure measurements. We simulated the distribution of residual magnetic fields over time under different collision conditions using UrQMD for Au+Au collisions at sqrt(sNN)=200 GeV and calculated their effects on the azimuthal modulation ( ) of photoproduced rho0. Our results show that in peripheral collisions, the field significantly alters the for photoproduced rho0 with pT ~ 0.1 GeV/c. This provides key insights for future nuclear structure studies via photoproduction in peripheral collisions.

hep-ph↗

arXiv2025

Rescattering effects on spin-interference for $\rho^{0}$ photoproduction in heavy-ion collisions

Recent measurements by various experiments in ultra-peripheral collisions have observed spin-interference in $\rho^{0}$ photoproduction, marking a breakthrough in Fermi-scale quantum interference experiments. Building on this, STAR extended the measurement to hadronic heavy-ion collisions, where significant rescattering effects on $\rho^{0}$ mesons were expected. In this study, we investigate how these rescattering effects influence the measurement of spin-interference. By embedding $\rho^{0}$ mesons produced via photoproduction, modeled by the Vector Meson Dominance model, into the Ultrarelativistic Quantum Molecular Dynamics framework, we estimate the impact on the $\cos2\phi$ and $\cos4\phi$ modulations, where $\phi$ is the angle between $\rho^{0}$ and one of the daughters' ($\pi^{\pm}$) transverse momentum. The results indicate a significant suppression of the $\cos2\phi$ modulation, while the $\cos4\phi$ modulation remains largely unaffected, which provides insight for understanding the difference due to rescattering effects between experimental measurements and theoretical predictions for $\rho^{0}$ photoproduction in heavy-ion collisions.

nucl-th↗

arXiv2025

Probing Gluon Shadowing in Heavy Nuclei through Bayesian Reweighting of J/$\psi$ Photoproduction in Ultra-Peripheral Collisions

The gluon distribution in nuclei plays a pivotal role in understanding quantum chromodynamics (QCD) under extreme nuclear environments, yet remains poorly constrained compared to quark distributions. Coherent \jpsi photoproduction in ultra-peripheral heavy-ion collisions ($\gamma + A \rightarrow \mathrm{J}/\psi + A$) provides a unique solution to this challenge, serving as a sensitive probe of nuclear gluon densities. In this study, we perform Bayesian reweighting on the EPPS21 and nCTEQ15 sets of nuclear parton distribution functions (nPDF) by incorporating coherent \jpsi photoproduction measurements from both RHIC and LHC. The Bayesian-reweighted gluon modification factors $\mathrm{R_g^{A}}(x, Q^2 = 2.4\ \mathrm{GeV}^2)$ reveal pronounced nuclear shadowing in the Pb nuclei, with $\mathrm{R_g^{\mathrm{Pb}}} \approx 0.60$ at $x = 10^{-4}$, while simultaneously achieving a great reduction of the uncertainties in the density of the gluon across the critical Bjorken-$x$ range $10^{-5} < x < 10^{-3}$ compared to initial predictions of the nPDF. This work establishes coherent \jpsi photoproduction as a precision tool for gluon nPDF extraction, overcoming traditional deep-inelastic scattering limitations through perturbative QCD-calibrated probes. The constrained nPDFs demonstrate improved consistency with the experimental data across collider energies, particularly in the shadowing-dominated regime.

hep-ph↗

arXiv2024

Coalescence formation of muonic atoms at RHIC

The discovery of exotic mounic atoms, including antimatter hydrogen muonic atoms and kaon mounic atoms, constitutes a milestone in our ability to make and study new forms of matter. Relativistic heavy-ion collisions provide the only likely condition for production and detection of these exotic atoms. Taking a Coulomb correlations into account from the time of the fireball freeze-out until the formation of a stable atom has dramatic consequence on the expected yields of these atoms. When the coalescence model with the assumption of quantum wave function localization is applied to the formation of muonic atoms, we find that the atom yields are about two orders of magnitude higher than previously predicted.

hep-ph↗

arXiv2024

Centrality Manipulation in Exclusive Photoproduction at the Electron-Ion Collider

In the context of future electron-ion collision experiments, particularly the Electron-Ion Collider (EIC) and the Electron-Ion Collider in China (EicC), investigating exclusive photoproduction processes is of paramount importance. These processes offer a unique opportunity to probe the gluon structure of nuclei across a broad range of Bjorken-$x$, facilitating measurements of nuclear shadowing and searches for gluon saturation and/or the color glass condensate. This paper explores the potential of utilizing neutron tagging from Coulomb excitation of nuclei to effectively determine centrality for exclusive photoproduction in electron-ion collisions. By developing the equivalent photon approximation for fast-moving electrons, this work incorporates a coordinate-space-dependent photon flux distribution, elucidating the relationship between the photon transverse momentum distribution and collision impact parameter. Leveraging spatial information from the photon flux, the differential cross section for Coulomb excitation of nuclei is derived. Our calculations demonstrate that neutron tagging can significantly alter impact parameter distributions, thereby providing a robust method for centrality manipulation in electron-ion collisions. This study contributes essential baseline and strategies for exploring the impact parameter dependence of exclusive photoproduction, offering novel insights for experimental design and data analysis. Ultimately, it provides additional information to better visualize the gluon distribution within the nucleus.

hep-ph↗

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

Exploring the photoproduction of $\rho$ and $\phi$ in hadronic heavy-ion collisions

Significant enhancements of J/$\psi$ production have been observed by various experiments at RHIC and LHC for very low transverse momenta in peripheral heavy-ion collisions, which has ignited a surge of investigations into photon-induced processes in hadronic heavy-ion collisions (HHICs). Within this wave of research enthusiasm, the search for more photon induced products in HHICs becomes paramount. In this paper, we perform the calculation of the $\rho$ and $\phi$ production resulting from photon-nucleus interactions in HHICs, which are crucial probes for studying the properties of Quark-Gluon Plasma (QGP) in HHICs. Our study reveals that, in comparison to hadronic production, the photon-induced production of $\rho$ and $\phi$ does not reach the same level of significance as that observed in J/$\psi$ production. Nevertheless, it remains substantial, especially in peripheral collisions, holding great promise for experimental verification in the imminent future.

hep-ph↗