arXiv subjects

Z. Xie

Publications and source records attributed to Z. Xie.

At least 19 recordsLinked to original sources

arXiv2026

Wavelength-resolved small-angle neutron spectroscopy of spin waves in MnSi under pressure

We report wavelength-resolved spin-wave small-angle neutron scattering (SWSANS) on the time-of-flight SANS instrument BL01 at the China Spallation Neutron Source and extend the method to pressure-cell measurements of MnSi. MnSi is used as a benchmark B20 helimagnet because its helimagnetic order and spin-wave stiffness are well characterized at ambient pressure. In a fixed magnetic field, the time-of-flight measurement provides a spectrum of neutron wavelengths. For each detector branch $s=\pm1$, the intensity profile is recentered relative to the wavelength-dependent Bragg angle $\theta_B (\lambda) = k_s \lambda / 2\pi$, and the cutoff angle $\theta_C (\lambda)$ is extracted in the local branch coordinate. The cutoff-derived spin-wave stiffness $A$ is obtained from a linear fit of $\theta_C^2$ as a function of $\lambda^2$. Ambient-pressure measurements reproduce the known stiffness scale of MnSi. Structural SANS at ambient pressure and at nominal 5 and 11 kbar verifies the magnetic state and provides an internal pressure-state check for the pressure-cell measurements. At nominal 11 kbar, within the present cutoff model, the cutoff-derived stiffness is substantially reduced, whereas the structural field scale $H_{C2}$ remains high. This contrast shows that $A$ cannot be inferred from static structural parameters alone under pressure. To our knowledge, these measurements constitute the first SWSANS implementation on a pulsed neutron source and the first SWSANS determination of spin-wave stiffness under pressure. The experiment also shows that reliable high-pressure SWSANS on a pulsed source requires high source brilliance, stable wavelength-dependent normalization, and sufficient statistics in each wavelength window.

cond-mat.str-el↗

arXiv2026

Revisiting identified-particle $p_{\mathrm{T}}$ spectra using the Boltzmann-Gibbs blast-wave model in a Bayesian inference framework

We perform a Bayesian analysis of transverse momentum ($p_{\mathrm{T}}$) spectra of identified particles, i.e., pions, kaons, and protons, at midrapidity in Au+Au collisions and Pb+Pb collisions using the Boltzmann-Gibbs blast-wave (BGBW) model. We investigate whether it is possible to simultaneously describe the $p_{\mathrm{T}}$ spectra of identified particles without imposing the particle species-dependent $p_{\mathrm{T}}$ fit ranges -- a practice that was followed in conventional blast-wave model studies to achieve reasonable simultaneous fits. Using Bayesian analysis, our results indicate that a simultaneous description of the $p_{\mathrm{T}}$ spectra of pions, kaons, and protons is feasible without imposing the particle species-dependent $p_{\mathrm{T}}$ fit ranges, for Au+Au collisions up to the available data ($\sim$2 GeV/c) and for Pb+Pb collisions up to 3 GeV/c. The extracted parameters remain broadly consistent with those obtained from conventional BGBW simultaneous fits, while the extension of the fit range leads to moderate changes in some parameters. Furthermore, Bayesian analysis yields well-constrained posterior distributions for the kinetic freeze-out temperature $T_{kin}$, the average transverse flow velocity $\langle \beta_{\mathrm{T}}\rangle$, and the exponent of the velocity profile $n$ and shows their correlations transparently. We suggest that the BGBW model in a Bayesian inference framework proposed can be applied in future data analyses to simultaneously describe the $p_{\mathrm{T}}$ spectra of identified particles and extract the relevant information about the collision system.

nucl-th↗

arXiv2026

Particle productions in $p\bar{p}$ collisions in the PACIAE 4.0 model

We investigate the particle production in proton-antiproton ($p\bar{p}$) collisions using the PACIAE 4.0 model. The pseudorapidity density distributions ($dN_{\text{ch}}/d\eta$) and transverse momentum ($p_T$) spectra of charged particles from nonsingle diffractive (NSD) $p\bar{p}$ collisions agree well with the experimental data when using model parameters previously determined from nonsingle diffractive proton-proton ($pp$) collisions. Furthermore, we systematically compare results from both inelastic (INEL) and nonsingle diffractive $p\bar{p}$ and $pp$ collisions at the same energy to study the effect of the initial state (matter vs. antimatter) on the transverse momentum spectra of identified particles. Our results show that the net baryon-number difference in the initial state significantly enhances nucleon production at low collision energies, while its effect becomes negligible for high-multiplicity particles or at high collision energies, as expected. These findings further prove that the PACIAE 4.0 model is a versatile and reliable tool for studying high-energy collision physics.

hep-ph↗

arXiv2025

Pseudorapidity dependence of charged particles production in non-single diffractive $pp$ collisions in the PACIAE 4.0 model

Studying experimental observables is a key benchmark for validating theoretical models in high energy physics. In this work, we employ the PACIAE 4.0 model to simulate non-single diffractive proton-proton ($pp$) collisions at center-of-mass energies of 0.9, 2.36, and 7 TeV, comparing the results with Compact Muon Solenoid (CMS) experimental data on charged-particle pseudorapidity densities and transverse momentum spectra across different pseudorapidity bins, respectively. Our results show good agreement with the CMS data, particularly only using a single set of parameters for all collision energies. This demonstrates that the PACIAE 4.0 model can serve as a reliable tool for systematically studying the physics of NSD $pp$ collisions.

hep-ph↗

arXiv2025

Pseudorapidity density distributions of charged particles and transverse momentum spectra of identified particles in pp collisions in PACIAE 4.0 model

The pseudorapidity density distributions of charged particles and the transverse momentum spectra of identified particles in proton-proton (pp) collisions at the center-of-mass energies ranging from $\sqrt{s}=200$ GeV to 13 TeV have been systematically studied using the newly released parton and cascade model PACIAE 4.0 based on PYTHIA 8.3. The available experimental data are well reproduced across all analyzed aspects. This theoretical method can be easily extended to anywhere the experimental data for pp collisions are currently unavailable. Furthermore, since pp collisions serve as the baseline for heavy-ion collisions, our results can provide a valuable resource for both experimentalists and theorists.

hep-ph↗

arXiv2023

Study of Silicon Photomultiplier External Cross-Talk

Optical cross-talk is a critical characteristic of Silicon Photomultipliers (SiPMs) and represents a significant source of the excess noise factor, exerting a substantial influence on detector performance. During the avalanche process of SiPMs, photons generated can give rise to both internal cross-talk within the same SiPM and external cross-talk when photons escape from one SiPM and trigger avalanches in others. In scenarios where SiPMs are arranged in a compact configuration and positioned facing each other, the external cross-talk could even dominate the cross-talk phenomenon. This paper investigates two distinct methods for measuring external cross-talk: the counting method, which involves operating SiPMs face-to-face and measuring their coincident signals, and the reflection method, which employs a highly reflective film attached to the surface of the SiPMs. External cross-talk measurements have been conducted on several types of SiPMs, including Vacuum Ultra-Violet (VUV) sensitive SiPMs that Fondazione Bruno Kessler (FBK) and Hamamatsu Photonics Inc (HPK) produced for nEXO as well as visible-sensitive SiPMs provided by FBK, HPK and SensL Technologies Ltd (SenSL) for JUNO-TAO. The results reveal a significant presence of external cross-talk in all tested SiPMs, with HPK's SiPMs exhibiting a dominant external cross-talk component due to the implementation of optical trenches that effectively suppress internal cross-talk. Furthermore, we found that the number of fired pixels resulting from internal cross-talk can be described by combining Geometric and Borel models for all tested SiPMs, while the external cross-talk can be predicted using a pure Borel model. These distinct probability distributions lead to different excess noise factors, thereby impacting the detector performance in varying ways.

physics.ins-det↗

arXiv2023

Exploring Solute Behavior and Texture Selection in Magnesium Alloys at the Atomistic Level

This study advances our understanding of how chemical binding and solute distribution impact grain boundary segregation behavior and subsequent annealing texture modification in lean Mg-X-Zn alloys (X = RE or Ca). Notably, differences in Ca and Gd solute behavior at grain boundaries were revealed, where Ca exhibited stronger binding to vacancy sites than Gd, resulting in elevated Ca segregation and an RD-TD-type texture. The introduction of Zn showed significant synergistic effects on solute clustering, with Gd-Zn pairs forming more favorably than Ca-Zn pairs, leading to a strong synergy between Zn and Gd. This promoted their co-segregation and high concentration at the grain boundary, generating a unique TD-spread texture. In contrast, weaker binding in Ca-Zn pairs did not affect Ca segregation but influenced Zn segregation, which underscores the importance of solute binding behavior in alloy design concepts. Additionally, the combined atomicscale experiments and ab initio predictions provide strong evidence that selective texture development in Mg alloys is tied to heterogeneous solute-boundary interactions, where the sensitivity of the binding energy to volumetric strain affects solute segregation at grain boundaries, resulting in varying grain boundary mobilities and specific texture component growth. It also emphasizes that solute behavior in clustering and segregation is influenced not only by atomic size but also by chemical binding strength with vacancies or co-added Zn.

cond-mat.mtrl-sci↗

arXiv2023

Origins of limited non-basal plasticity in the {\mu}-phase at room temperature

We unveil a new non-basal slip mechanism in the {\mu}-phase at room temperature using nanomechanical testing, transmission electron microscopy and atomistic simulation. The (1-105) planar faults with a displacement vector of 0.07[-5502] can be formed by dislocation glide. They do not disrupt the Frank-Kasper packing and therefore enable the accommodation of plastic strain at low temperatures without requiring atomic diffusion. The intersections between the (1-105) planar faults and basal slip result in stress concentration and crack nucleation during loading.

cond-mat.mtrl-sci↗

arXiv2023

Does Feedback from Supermassive Blackhole Co-evolve With Host In Type 2 Quasars?

The feedback from accretion of central supermassive black holes (SMBHs) is a hot topic in the co-evolution of the SMBHs and their host galaxies. By tracing the large scale outflow by the line profile and bulk velocity shift of $[ \rm O~{\scriptsize III}]~ λ5007$, the evolutionary role of outflow is studied here on a large sample of 221 type 2 quasars (QSO2s) extracted from Reyes et al. By following our previous study on local Seyfert 2 galaxies, the current spectral analysis on the SDSS spectroscopic database enables us to arrive at following results: (1) by using the Lick indices, we confirm that QSO2s are on average associated with younger stellar populations than Seyfert galaxies; (2) QSO2s with a stronger outflow are tend to be associated with a younger stellar population, which implies a coevolution between the feedback from SMBH and the host in QSO2s; (3) although an occupation at the high $L_{\rm bol}/L_{\rm Edd}$ end, the QSO2s follow the $L_{\rm bol}/L_{\rm Edd}$-$D_{n}(4000)$ sequence established from local, less-luminous Seyfert galaxies, which suggests a decrease of accretion activity of SMBH and feedback as the circumnuclear stellar population continuously ages.

astro-ph.GA↗

arXiv2023

Plasticity of the Nb-rich μ-Co7Nb6 phase at room temperature and 600 °C

The μ-phase is a common precipitation phase in superalloys and it exists in a wide composition and temperature range. As such, we study the influences of composition and temperature on its plasticity by micropillar compression tests and transmission electron microscopy. The micropillars of the μ-Co7Nb6 phase deform plastically by basal slip at either room temperature or 600 oC. At room temperature, the Co-49Nb and Co-52Nb micropillars show high yield stresses and an abrupt large strain burst at the onset of yielding regardless of orientation, whereas the Co-54Nb micropillars oriented for basal slip yield at much lower stresses and show intermittent small strain bursts during plastic deformation. While the Co-49Nb micropillars deform by full dislocation slip on the basal plane at room temperature, the Co-54Nb micropillars deform by partial dislocation slip on the basal plane. At 600 oC, the Co-49Nb micropillars oriented for basal slip show stable and continuous plasticity and their critical resolved shear stress decreases dramatically. The plastic deformation of the Co-49Nb micropillars occurs via partial dislocation slip on the basal plane at 600 oC. Based on the geometric γ-surfaces for all potential basal slip planes, we explore where and why the glide of full and partial dislocations on the basal plane occurs in the μ-Co7Nb6 phase.

cond-mat.mtrl-sci↗

arXiv2021

The study of active geomagnetic shielding coils system for JUNO

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator (LS) detector for neutrino mass ordering and other neutrino physics research. The detector uses large-size $20$ inches photomultiplier tubes to detect photons from a liquid scintillator. The large PMTs are sensitive and easily affected such that the detection efficiency loses about 60$\%$ under the geomagnetic field intensity ($\sim$500 mG). It has a significantly negative effect on the detector performance, and a compensation system is necessary for geomagnetic field shielding. As permalloys are easily rusted in water, a better way for the geomagnetic shielding is to apply an active compensation coils system. The simulations show that a set of 32 circular coils can meet the experiment requirement. The residual magnetic field is less than 0.05 G in the Central Detector Photomultiplier Tube (CD-PMT) region (38.5-39.5 m in diameter). A prototype coil system with a 1.2 m was built to validate the simulation and the design. The measured data of prototype and simulation results are consistent with each other, and geomagnetic field intensity is effectively reduced by coils, verifying the shielding coils system design for JUNO. This study is expected to provide practical guidance for the PMT magnetic field shielding for future large-scale detector designs.

physics.ins-det↗

arXiv2021

Dislocation-mediated plasticity in the Al$_{2}$Cu θ-phase

The deformation behaviour of the intermetallic Al$_{2}$Cu-phase was investigated using atomistic simulations and micropillar compression, where slip on the unexpected {211} and {022} slip planes was revealed. Additionally, all possible slip systems for the intermetallic phases were further evaluated and a preference for the activation of slip systems based on their effective interplanar distances as well as the effective Burgers vector is proposed. The effective interplanar distance corresponds to the manually determined interplanar distance, whereas the effective Burgers vector takes a potential dislocation dissociation into account. This new order is: {211}1/2<111>, {022}1/2<111> and {022}<100>, {110}<001>, {310}<001>, {022}<011>, {110}1/2<111>, {112}<110> and {112}1/2<111> from high to low ratio of deff/beff. Also, data on the critical resolved shear stresses of several of these slip systems were measured.

cond-mat.mtrl-sci↗

arXiv2020

648 Hilbert space dimensionality in a biphoton frequency comb

Qubit entanglement is a valuable resource for quantum information processing, where increasing its dimensionality provides a pathway towards higher capacity and increased error resilience in quantum communications, cluster computation and quantum phase measurements. Time-frequency entanglement, a continuous variable subspace, enables the high-dimensional encoding of multiple qubits per particle, bounded only by the spectral correlation bandwidth and readout timing jitter. Extending from a dimensionality of two in discrete polarization variables, here we demonstrate a hyperentangled, mode-locked, biphoton frequency comb with a time-frequency Hilbert space dimensionality of at least 648. Hong-Ou-Mandel revivals of the biphoton qubits are observed with 61 time-bin recurrences, biphoton joint spectral correlations over 19 frequency-bins, and an overall interference visibility of the high-dimensional qubits up to 98.4%. We describe the Schmidt mode decomposition analysis of the high-dimensional entanglement, in both time- and frequency-bin subspaces, not only verifying the entanglement dimensionality but also examining the time-frequency scaling. We observe a Bell violation of the high-dimensional qubits up to 18.5 standard deviations, with recurrent correlation-fringe Clauser-Horne-Shimony-Holt S-parameter up to 2.771. Our biphoton frequency comb serves as a platform for dense quantum information processing and high-dimensional quantum key distribution.

quant-ph↗

arXiv2020

Pulse Shape Particle Identification by a Single Large Hemispherical Photo-Multiplier Tube

In neutrino experiments, hemispherical photomultiplier tubes (PMTs) are often used to cover large surfaces or volumes to maximize the photocathode coverage with a minimum number of channels. Instrumentation is often coarse, and neutrino event reconstruction and particle identification (PID) is usually done through the morphology of PMT hits. In future neutrino experiments, it may be desirable to perform PID from a few hits, or even a single hit, by utilizing pulse shape information. In this report, we study the principle of pulse shape PID using a single 10-inch hemispherical PMT in a spherical glass housing for future neutrino telescopes. We use the Fermilab Test Beam Facility (FTBF) MTest beamline to demonstrate that with pulse shape PID, statistical separation is possible to distinguish 2 GeV electrons from 8 GeV pions, where the total charge deposition is ~20 PE in our setup. Such techniques can be applied to future neutrino telescopes focusing on low energy physics, including the IceCube-Upgrade.

physics.ins-det↗

arXiv2019

On a Simple and Effective Thermal Open Boundary Condition for Convective Heat Transfer Problems

We present an effective thermal open boundary condition for convective heat transfer problems on domains involving outflow/open boundaries. This boundary condition is energy-stable, and it ensures that the contribution of the open boundary will not cause an ``energy-like'' temperature functional to increase over time, irrespective of the state of flow on the open boundary. It is effective in coping with thermal open boundaries even in flow regimes where strong vortices or backflows are prevalent on such boundaries, and it is straightforward to implement. Extensive numerical simulations are presented to demonstrate the stability and effectiveness of our method for heat transfer problems with strong vortices and backflows occurring on the open boundaries. Simulation results are compared with previous works to demonstrate the accuracy of the presented method.

physics.flu-dyn↗

arXiv2010

Persistent storage of non-event data in the CMS databases

In the CMS experiment, the non event data needed to set up the detector, or being produced by it, and needed to calibrate the physical responses of the detector itself are stored in ORACLE databases. The large amount of data to be stored, the number of clients involved and the performance requirements make the database system an essential service for the experiment to run. This note describes the CMS condition database architecture, the data-flow and PopCon, the tool built in order to populate the offline databases. Finally, the first experience obtained during the 2008 and 2009 cosmic data taking are presented.

physics.ins-det↗

arXiv2003

POOL File Catalog, Collection and Metadata Components

The POOL project is the common persistency framework for the LHC experiments to store petabytes of experiment data and metadata in a distributed and grid enabled way. POOL is a hybrid event store consisting of a data streaming layer and a relational layer. This paper describes the design of file catalog, collection and metadata components which are not part of the data streaming layer of POOL and outlines how POOL aims to provide transparent and efficient data access for a wide range of environments and use cases - ranging from a large production site down to a single disconnected laptops. The file catalog is the central POOL component translating logical data references to physical data files in a grid environment. POOL collections with their associated metadata provide an abstract way of accessing experiment data via their logical grouping into sets of related data objects.

cs.DB↗

arXiv2003

Giant Magnetoimpedance of Glass-Covered Amorphous Microwires of Co-Mn-Si-B and Co-Si-B

A study of magnetic hysteresis and Giant magnetoimpedance (GMI) in amorphous glass covered Co-Si-B and Co-Mn-Si-B wires is presented. The wires, about 10 microns in diameter, were obtained by glass-coated melt spinning technique. Samples with positive magnetostriction (MS) have a rectangular bistable hysteresis loop. A smooth hysteresis loop is observed for wires with nearly zero MS. When MS is negative, almost no hysteresis is observed. The GMI was measured in the frequency range between 20 Hz and 30 MHz. The shapes of the impedance versus field curves are qualitatively similar to each other for both positive and zero MS samples. Impedance is maximum at zero field, and decreases sharply in the range 10-20 Oe. For the negative MS wires, when the driving current is small, the impedance is maximum at a finite external field. The position of the maximum approaches zero with increasing current. The contributions of the moment rotation and domain wall motion in the three cases are discussed.

cond-mat.mtrl-sci↗