arXiv subjects

Wei-Dong Li

Publications and source records attributed to Wei-Dong Li.

15 recordsLinked to original sources

arXiv2023

An approach to study interactions of antineutrons with CsI at a $J/ψ$ factory

Cesium Iodide (CsI) crystals are widely used in high-energy physics for their scintillation properties that enable detection of charged and neutral particles via direct and indirect ionization and form the basis of electromagnetic calorimeters. However, knowledge of antineutron interactions with CsI is limited due to the difficulty of obtaining sources of antineutron of sufficient intensity and energy definition. As antineutron are abundantly produced by many processes it would be particularly useful to improve understanding of the interactions of antineutrons with CsI crystals. We propose to use the decay $J/ψ\to pπ^-\bar{n}$ at the BEPCII $J/ψ$ factory as a source of antineutrons using the BESIII detector with a CsI target added between the beam pipe and the detector. The BESIII Monte Carlo simulation with varying thicknesses of CsI target is used to validate the approach and optimize the target thickness. Selecting $pπ^-$ charged particle tracks from the Monte Carlo we obtain clean antineutron samples with well defined momentum and direction. The selection efficiency, momentum and angular resolutions, as well as the interaction probability between antineutron and the CsI target are estimated. As the CsI thickness is increased more antineutron CsI interactions are obtained,however the quality of the $pπ^-$ selection is degraded. The Monte Carlo study yields an optimum thickness that balances these effects. This approach can be applied to similar experiments with other types of target materials to measure baryons such as liquid hydrogen/deuterium and $Λ/Ξ$ hyperons.

hep-ex↗

arXiv2022

Degenerate Rabi spectroscopy of the Floquet engineered optical lattice clock

Simulating physics with large SU(N) symmetry is one of the unique advantages of Alkaline-earth atoms.Introducing periodical driving modes to the system may provide more rich SU(N) physics that static one could not reach. However, whether the driving modes will break the SU(N) symmetry is still lack of discussions. Here we experimentally study a Floquet engineered degenerate Sr-87 optical lattice clock (OLC) by periodically shaking the lattice. With the help of Rabi spectroscopy, we find that the atoms at different Zeeman sublevels are tuned by the same driven function. Meanwhile, our experimental results suggest that uniform distribution among the sublevels will not change despite the driving. Our experimental demonstrations may pave the way to implementation of FE on tailoring the SU(N) physics in OLC system.

cond-mat.quant-gas↗

arXiv2021

Generalized Bell-like inequality and maximum violation for multiparticle entangled Schrödinger-cat-states of spin-s

This paper proposes a generalized Bell-like inequality (GBI) for multiparticle entangled Schrödinger-cat--states of arbitrary spin-$s$. Based on quantum probability statistics the GBI and violation are formulated in an unified manner with the help of state density operator, which can be separated to local and non-local parts. The local part gives rise to the inequality, while the non-local part is responsible for the violation. The GBI is not violated at all by quantum average except the spin-$1/2$ entangled states. If the measuring outcomes are restricted in the subspace of spin coherent state (SCS), namely, only the maximum spin values $\pm s$, the GBI is still meaningful for the incomplete measurement. With the help of SCS quantum probability statistics, it is proved that the violation of GBI can occur only for half-integer spins but not integer spins. Moreover, the maximum violation bound depends on the number parity of entangled particles, that it is $1/2$ for the odd particle-numbers while $1$ for even numbers.

quant-ph↗

arXiv2021

The time-domain Landau-Zener-Stuckelberg-Majorana interference in optical lattice clock

The interference between a sequence of Landau-Zener (LZ) transitions can produce Rabi oscillations(LZROs). This phenomenon is a kind of time-domain Landau-Zener-Stuckelberg-Majorana (LZSM) interference. However, experimental demonstrations of this LZSM interference induced Rabi oscillation are extremely hard due to the short coherence time of the driven quantum system. Here, we study theoretically the time-domain LZSM interference between the clock transition in one-dimensional (1D) Sr-87 optical lattice clock (OLC) system. With the help of both the adiabatic-impulse model and Floquet numerical simulation method, the LZROs with special step-like structure are clearly found both in fast- and slow-passage limit in the real experiment parameter regions. In addition, the dephasing effect caused by the system temperature can be suppressed with destructive interference in the slow-passage limit. Finally, we discuss the possible Bloch-Siegert shift while the pulse time is away from the half-integer and integer periods. Our work provides a clear roadmap to observe the LZROs on the OLC platform.

cond-mat.quant-gas↗

arXiv2021

Rabi Spectroscopy and Sensitivity of a Floquet Engineered Optical Lattice Clock

We periodically modulate the lattice trapping potential of a $^{87}$Sr optical clock to Floquet engineer the clock transition. In the context of atomic gases in lattices, Floquet engineering has been used to shape the dispersion and topology of Bloch quasi-energy bands. Differently from these previous works manipulating the external (spatial) quasi-energies, we target the internal atomic degrees of freedom. We shape Floquet spin quasi-energies and measure their resonance profiles with Rabi spectroscopy. We provide the spectroscopic sensitivity of each band by measuring the Fisher information and show that this is not depleted by the Floquet dynamical modulation. The demonstration that the internal degrees of freedom can be selectively engineered by manipulating the external degrees of freedom inaugurates a novel device with potential applications in metrology, sensing and quantum simulations.

cond-mat.quant-gas↗

arXiv2016

Track segment finding with CGEM-IT and matching to tracks in ODC

The relative differences in coordinates of Cylindrical-Gas-Electron-Multiplier-Detector-based Inner Tracker (CGEM-IT) clusters are studied to search for track segments in CGEM-IT. With the full simulation of single muon track samples, clear patterns are found and parameterized for the correct cluster combinations. The cluster combinations satisfying the patterns are selected as track segment candidates in CGEM-IT with an efficiency higher than 99%. The parameters of the track segments are obtained by a helix fitting. Some chi-squared quantities, evaluating the differences in track parameters between the track segments in CGEM-IT and the tracks found in Outer-Drift-Chamber (ODC), are calculated and used to match them. Proper chi-squared requirements are determined as a function of transverse momentum and the matching efficiency is found reasonable.

physics.ins-det↗

arXiv2015

Study of cluster reconstruction and track fitting algorithms for CGEM-IT at BESIII

Considering the aging effects of existing Inner Drift Chamber (IDC) of BES\uppercase\expandafter{\romannumeral3}, a GEM based inner tracker is proposed to be designed and constructed as an upgrade candidate for IDC. This paper introduces a full simulation package of CGEM-IT with a simplified digitization model, describes the development of the softwares for cluster reconstruction and track fitting algorithm based on Kalman filter method for CGEM-IT. Preliminary results from the reconstruction algorithms are obtained using a Monte Carlo sample of single muon events in CGEM-IT.

physics.ins-det↗

arXiv2014

Study of the calibration of X-T relation for the BESIII drift chamber

This paper introduces the calibration of the time-to-distance relation for the BESIII drift chamber. The parameterization of the time-to-distance relation is presented. The studies of left-right asymmetry and the variation with the entrance angle are performed. The impact of dead channels on the time-to-distance relation is given special attention in order to reduce the shifts of the measured momenta for the tracks passing near dead cells. Finally we present the spatial resolution (123 μm) for barrel Bhabha events (|cosθ|<0.8) from J/ψ data taken in 2012.

physics.ins-det↗

arXiv2012

First-principles DFT+\emph{U} study of structural and electronic properties of PbCrO$_{3}$

We have performed a systematic first-principles investigation to calculate the structural, electronic, and magnetic properties of PbCrO$_{3}$, CrPbO$_{3}$ as well as their equiproportional combination. The local density approximation (LDA)$+U$ and the generalized gradient approximation$+U$ theoretical formalisms have been used to account for the strong on-site Coulomb repulsion among the localized Cr 3d electrons. By choosing the Hubbard \emph{U} parameter around 4 eV, ferromagnetic, and/or antiferromagnetic ground states can be achieved and our calculated lattice constants, bulk moduli, and equation of states are in good agreement with recent experiments [W. Xiao \emph{et al.}, PNAS \textbf{107}, 14026 (2010)]. The bonding nature of B$-$O bonds in these ABO$_{3}$ compounds exhibit evident covalent character and our electron transferring study indicates that the ionicity shows decreasing trend with increasing fraction of CrO$_{6/2}$ octahedron within the PbCrO$_{3}$-CrPbO$_{3}$ random compounds. The lengthes of B$-$O bonds determine their lattice parameters, thus, clearly indicates that the abnormally large volume and compressibility is due to the contain of CrPbO$_{3}$ in the experimental sample and the transition of PbO$_{6/2}$ octahedron to CrO$_{6/2}$ upon compression.

cond-mat.str-el↗

arXiv2011

First-principles calculations of phase transition, elasticity, and thermodynamic properties for TiZr alloy

tructural transformation, pressure dependent elasticity behaviors, phonon, and thermodynamic properties of the equiatomic TiZr alloy are investigated by using first-principles density-functional theory. Our calculated lattice parameters and equation of state for $α$ and $ω$ phases as well as the phase transition sequence of $α$$\mathtt{\rightarrow}$$ω$$\mathtt{\rightarrow}$$β$ are consistent well with experiments. Elastic constants of $α$ and $ω$ phases indicate that they are mechanically stable. For cubic $β$ phase, however, it is mechanically unstable at zero pressure and the critical pressure for its mechanical stability is predicted to equal to 2.19 GPa. We find that the moduli, elastic sound velocities, and Debye temperature all increase with pressure for three phases of TiZr alloy. The relatively large $B/G$ values illustrate that the TiZr alloy is rather ductile and its ductility is more predominant than that of element Zr, especially in $β$ phase. Elastic wave velocities and Debye temperature have abrupt increase behaviors upon the $α$$\mathtt{\rightarrow}$$ω$ transition at around 10 GPa and exhibit abrupt decrease feature upon the $ω$$\mathtt{\rightarrow}$$β$ transition at higher pressure. Through Mulliken population analysis, we illustrate that the increase of the \emph{d}-band occupancy will stabilize the cubic $β$ phase. Phonon dispersions for three phases of TiZr alloy are firstly presented and the $β$ phase phonons clearly indicate its dynamically unstable nature under ambient condition. Thermodynamics of Gibbs free energy, entropy, and heat capacity are obtained by quasiharmonic approximation and Debye model.

cond-mat.mtrl-sci↗

arXiv2010

First-principles calculations of phase transition, low elastic modulus, and superconductivity for zirconium

The elasticity, dynamic properties, and superconductivity of $α$, $ω$, and $β$ Zr are investigated by using first-principles methods. Our calculated elastic constants, elastic moduli, and Debye temperatures of $α$ and $ω$ phases are in excellent agreement with experiments. Electron-phonon coupling constant $λ$ and electronic density of states at the Fermi level $N$(\emph{E}$_{\rm{F}}$) are found to increase with pressure for these two hexagonal structures. For cubic $β$ phase, the critical pressure for mechanical stability is predicted to be 3.13 GPa and at \emph{P}=4 GPa the low elastic modulus ($E$=31.97 GPa) can be obtained. Besides, the critical pressure for dynamic stability of $β$ phase is achieved by phonon dispersion calculations to be $\mathtt{\sim}$26 GPa. Over this pressure, $λ$ and $N$(\emph{E}$_{\rm{F}}$) of $β$ phase decrease upon further compression. Our calculations show that the large value of superconducting transition temperature $\emph{T}_{\rm{c}}$ at 30 GPa for $β$ Zr is mainly due to the TA1 soft mode. Under further compression, the soft vibrational mode will gradually fade away.

cond-mat.mtrl-sci↗

arXiv2010

Structural, mechanical, thermodynamic, and electronic properties of thorium hydrides from first principles

We perform first-principles calculations of the structural, electronic, mechanical, and thermodynamic properties of thorium hydrides (ThH$_{2}$ and Th$_{4}$H$_{15}$) based on the density functional theory with generalized gradient approximation. The equilibrium geometries, the total and partial densities of states, charge density, elastic constants, elastic moduli, Poisson's ratio, and phonon dispersion curves for these materials are systematically investigated and analyzed in comparison with experiments and previous calculations. These results show that our calculated equilibrium structural parameters are well consistent with experiments. The Th$-$H bonds in all thorium hydrides exhibit weak covalent character, but the ionic properties for ThH$_{2}$ and Th$_{4}$H$_{15}$ are different due to their different hydrogen concentration. It is found that while in ThH$_{2}$ about 1.5 electrons transfer from each Th atom to H, in Th$_{4}$H$_{15}$ the charge transfer from each Th atom is around 2.1 electrons. Our calculated phonon spectrum for the stable body-centered tetragonal phase of ThH$_{2}$ accords well with experiments. In addition we show that ThH$_{2}$ in the fluorite phase is mechanically and dynamically unstable.

cond-mat.mtrl-sci↗

arXiv2004

Nonlinear Krönig-Penney model

We study the nonlinear Schrödinger equation with a periodic delta-function potential. This realizes a nonlinear Krönig-Penney model, with physical applications in the context of trapped Bose-Einstein condensate alkaly gases and in the transmission of signals in optical fibers. We find analytical solutions of zero-current Bloch states. Such wave-functions have the same periodicity of the potential, and, in the linear limit, reduce to the Bloch functions of the Krönig-Penney model. We also find new classes of solutions having a periodicity different from that of the external potential. We calculate the chemical potential of such states and compare it with the linear excitation spectrum.

cond-mat.other↗

arXiv2003

Energy band structure and intrinsic coherent properties in two weakly linked Bose Einstein Condensates

The energy band structure and energy splitting due to quantum tunneling in two weakly linked Bose-Einstein condensates were calculated by using the instanton method. The intrinsic coherent properties of Bose Josephson junction were investigated in terms of energy splitting. For $E_{C}/E_{J}\ll 1$, the energy splitting is small and the system is globally phase coherent. In the opposite limit, $E_{C}/E_{J}\gg 1$, the energy splitting is large and the system becomes a phase dissipation. Our reslults suggest that one should investigate the coherence phenomna of BJJ in proper condition such as $E_{C}/E_{J}\sim 1$.

cond-mat.soft↗

arXiv2002

Exact calculation of the skyrmion lifetime in a ferromagnetic Bose condensate

The tunneling rate of a skyrmion in ferromagnetic spin-1/2 Bose condensates through an off-centered potential barrier is calculated exactly with the periodic instanton method. The prefactor is shown to depend on the chemical potential of the core atoms, at which level the atom tunnels. Our results can be readily extended to estimate the lifetime of other topological excitations in the condensate, such as vortices and monopoles.

cond-mat.soft↗