Central Pb Research Articles

Constraining hadronization mechanisms with [formula omitted] production ratios in Pb–Pb collisions at [formula omitted] TeV

The production of prompt Λc+ baryons at midrapidity (|y|<0.5) was measured in central (0–10%) and mid-central (30–50%) Pb–Pb collisions at the center-of-mass energy per nucleon–nucleon pair sNN=5.02 TeV with the ALICE detector. The results are more precise, more differential in centrality, and reach much lower transverse momentum (pT=1 GeV/c) with respect to previous measurements performed by the ALICE, STAR, and CMS Collaborations in nucleus–nucleus collisions, allowing for an extrapolation down to pT=0. The pT-differential Λc+/D0 ratio is enhanced with respect to the pp measurement for 4<pT<8 GeV/c by 3.7 standard deviations (σ), while the pT-integrated ratios are compatible within 1σ. The observed trend is similar to that observed in the strange sector for the Λ/KS0 ratio. Model calculations including coalescence or statistical hadronization for charm-hadron formation are compared with the data.

Thermal radiation and direct photon production measurements with dielectrons in Pb–Pb and pp collisions

The latest ALICE results on dielectron measurements in Pb–Pb collisions at √SNN = 5.02 TeV, and in minimum-bias (MB) and high-multiplicity (HM) pp collisions at √S = 13 TeV with LHC Run 2 data are reported. The results are compared to the predictions of dielectron yields from known hadronic sources and thermal radiation from the medium. The contribution of virtual direct photons is extracted from the data by fitting the measured invariant mass distributions. We present the direct to inclusive photon ratio, as well as the direct photon yield in both pp and central Pb–Pb collisions.

Association of Pressure Wave Reflections With Left Ventricular Mass: a Systematic Review and Meta-Analysis.

Pressure wave reflections (PWRs) within the circulation are assessed at various arterial sites by various noninvasive methods. We aimed at reviewing the conflicting data regarding the hypothesis that higher PWRs are associated with higher left ventricular mass and tested whether this association stands for all available indices of PWRs, all (proximal or distal to the heart) sites of assessment, and is modified by sex, age and heart rate. Based on a predefined protocol applying the Meta-Analysis of Observational Studies in Epidemiology (MOOSE) guidelines, we identified eligible for meta-analysis data regarding: augmentation index, augmentation pressure, backward pressure (Pb), reflection index, and their association with left ventricular mass index (19 studies, total population n=8686). We found statistically significant associations, independent from blood pressure level, for all indices of PWRs at all arterial sites (carotid augmentation index; odds ratio; standardized beta coefficient [β]: 0.14 [95% CI, 0.07% to 0.21%], per SD increase), radial augmentation index (β: 0.21; 0.11 to 0.31), central augmentation pressure (β: 0.15; 0.03 to 0.27), central Pb (β: 0.23; 0.05 to 0.42), and central reflection index (β: 0.14; 0.06 to 0.22), except for aortic augmentation index as estimated by generalized transfer functions. Meta-regression analysis showed that the association between carotid augmentation index and left ventricular mass was higher among populations with higher heart rate (P=0.036, beta: 0.017 [95% CI, 0.001 to 0.033]) and tended to be higher in middle-aged (P=0.07, beta: -0.001; -0.021 to 0.001). A clinically meaningful association between PWRs and left ventricular mass, assessed at either central or peripheral arterial sites by most available methods was shown, suggesting that PWR reduction strategies might be useful. Based on the present evidence, such trials should target middle-aged populations with high normal heart rate.

Simultaneous Analysis of Midrapidity pT Spectra of Identified Particle Species in Pb + Pb Collisions at snn = 2.76 TeV Using Tsallis Distribution with Transverse Flow

The midrapidity transverse momentum distributions of the charged pions, kaons, protons, and antiprotons in ten groups of centrality of Pb + Pb collisions at snn = 2.76 TeV, measured by the ALICE Collaboration, have been analyzed successfully using both thermodynamically consistent and non-consistent Tsallis distribution functions with transverse flow. The collision centrality dependencies of the extracted parameters of two kinds of Tsallis functions with transverse flow have been investigated. The significantly different behavior (growth rates) of ⟨βT⟩ in regions ⟨Npart⟩ &lt; 71 and ⟨Npart⟩ &gt; 71 with the temperature T0 becoming constant in region ⟨Npart⟩ &gt; 71 has been observed. This could indicate that ⟨Npart⟩ = 71 ± 5 (corresponding to ⟨dNch/dη⟩ = 205 ± 15) is a threshold border value of collision centrality for crossover phase transition from the dense hadronic state to the QGP state (or a mixed state of QGP and hadrons) in Pb + Pb collisions at snn = 2.76 TeV. This conjecture is supported further by the observed, significantly different correlations between T0 and ⟨βT⟩ parameters in the corresponding ⟨βT⟩ &lt; 0.44 and ⟨βT⟩ &gt; 0.44 ranges. The strong positive linear correlation between non-extensivity parameter q for pions and kaons, between q for pions and (anti)protons, and between q for kaons and (anti)protons has been obtained. The parameter q for all studied particle species has proven to be strongly anticorrelated with the average transverse flow velocity, ⟨βT⟩. Quite a large positive linear correlation has been obtained between the q of the studied particle species and temperature parameter T0. Analysis of q versus ⟨Npart⟩ dependencies for the studied particle species suggests that the highly thermalized and equilibrated QGP is produced in central Pb + Pb collisions at snn = 2.76 TeV with ⟨Npart⟩ &gt; 160.

Production of K*(892)0 and ϕ(1020) in pp and Pb−Pb collisions at sNN=5.02 TeV

The production of K$^{*}(892)^{0}$ and $\phi(1020)$ mesons in proton-proton (pp) and lead-lead (Pb-Pb) collisions at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV has been measured using the ALICE detector at the Large Hadron Collider (LHC). The transverse momentum ($p_{\mathrm{T}}$) distributions of K$^{*}(892)^{0}$ and $\phi(1020)$ mesons have been measured at midrapidity $(|y|<0.5)$ up to $p_{\mathrm{T}} = 20$ GeV$/c$ in inelastic pp collisions and for several Pb-Pb collision centralities. The collision centrality and collision energy dependence of the average transverse momenta agree with the radial flow scenario observed with stable hadrons, showing that the effect is stronger for more central collisions and higher collision energies. The $\mathrm{K^{*0}/K}$ ratio is found to be suppressed in Pb-Pb collisions relative to pp collisions: this indicates a loss of the measured K$^{*}(892)^{0}$ signal due to rescattering of its decay products in the hadronic phase. In contrast, for the longer-lived $\phi(1020)$ mesons, no such suppression is observed. The nuclear modification factors ($R_{\rm AA}$) of K$^{*}(892)^{0}$ and $\phi(1020)$ mesons are calculated using pp reference spectra at the same collision energy. In central Pb-Pb collisions for $p_{\rm T} > 8$ GeV$/c$, the $R_{\rm AA}$ values of K$^{*}(892)^{0}$ and $\phi(1020)$ are below unity and observed to be similar to those of pions, kaons, and (anti)protons. The $R_{\rm AA}$ values at high $p_{\mathrm T}$ ($>$~8 GeV$/c$) for K$^{*}(892)^{0}$ and $\phi(1020)$ mesons are in agreement within uncertainties for $\sqrt{s_\mathrm{NN}} = 5.02$ and 2.76 TeV.

Characterizing the initial conditions of heavy-ion collisions at the LHC with mean transverse momentum and anisotropic flow correlations

Correlations between mean transverse momentum [pT] and anisotropic flow coefficients v2 or v3 are measured as a function of centrality in Pb–Pb and Xe–Xe collisions at sNN=5.02 TeV and 5.44 TeV, respectively, with ALICE. In addition, the recently proposed higher-order correlation between [pT], v2, and v3 is measured for the first time, which shows an anticorrelation for the presented centrality ranges. These measurements are compared with hydrodynamic calculations using IP-Glasma and TRENTo initial-state shapes, the former based on the Color Glass Condensate effective theory with gluon saturation, and the latter a parameterized model with nucleons as the relevant degrees of freedom. The data are better described by the IP-Glasma rather than the TRENTo based calculations. In particular, Trajectum and JETSCAPE predictions, both based on the TRENTo initial state model but with different parameter settings, fail to describe the measurements. As the correlations between [pT] and vn are mainly driven by the correlations of the size and the shape of the system in the initial state, these new studies pave a novel way to characterize the initial state and help pin down the uncertainty of the extracted properties of the quark–gluon plasma recreated in relativistic heavy-ion collisions.

P T dispersion of inclusive jets in high-energy nuclear collisions* *Supported in part by Guangdong Major Project of Basic and Applied Basic Research (2020B0301030008), the National Natural Science Foundation of China (NSFC) (11935007, 12035007), the MOE Key Laboratory of Quark and Lepton Physics (CCNU) (QLPL2020P01)

In this study, we investigate the impact of jet quenching on the dispersion () of inclusive jets () in central Pb+Pb (0%–10%) collisions at TeV. The partonic spectrum in the initial hard scattering of elementary collisions is obtained by an event generator POWHEG+PYTHIA, which matches the next-to-leading order (NLO) matrix elements with parton showering, and the energy loss of a fast parton traversing through hot/dense QCD medium is calculated using Monte Carlo simulation within the Higher-Twist formalism of jet quenching in heavy-ion collisions. We present model calculations of the normalized distributions of inclusive jets in p+p and central Pb+Pb collisions at TeV, which offer good descriptions of ALICE measurements. It is shown that the distributions of inclusive jets in central Pb+Pb collisions shift significantly to a higher region relative to those in p+p collisions. Thus, the nuclear modification ratio of the distributions of inclusive jets is smaller than unity in the small region and larger than one in the large region. This behavior is caused by a more uneven distribution for jet constituents as well as the fraction alteration of quark/gluon initiated jets in heavy-ion collisions. The difference in distribution between groomed and ungroomed jets in Pb+Pb collisions is also discussed.

Does Sea Spray Aerosol Contribute Significantly to Aerosol Trace Element Loading? A Case Study From the U.S. GEOTRACES Pacific Meridional Transect (GP15)

AbstractAtmospheric deposition represents a major input for micronutrient trace elements (TEs) to the surface ocean and is often quantified indirectly through measurements of aerosol TE concentrations. Sea spray aerosol (SSA) dominates aerosol mass concentration over much of the global ocean, but few studies have assessed its contribution to aerosol TE loading, which could result in overestimates of “new” TE inputs. Low‐mineral aerosol concentrations measured during the U.S. GEOTRACES Pacific Meridional Transect (GP15; 152°W, 56°N to 20°S), along with concurrent towfish sampling of surface seawater, provided an opportunity to investigate this aspect of TE biogeochemical cycling. Central Pacific Ocean surface seawater Al, V, Mn, Fe, Co, Ni, Cu, Zn, and Pb concentrations were combined with aerosol Na data to calculate a “recycled” SSA contribution to aerosol TE loading. Only vanadium was calculated to have a SSA contribution averaging &gt;1% along the transect (mean of 1.5%). We derive scaling factors from previous studies on TE enrichments in the sea surface microlayer and in freshly produced SSA to assess the broader potential for SSA contributions to aerosol TE loading. Maximum applied scaling factors suggest that SSA could contribute significantly to the aerosol loading of some elements (notably V, Cu, and Pb), while for others (e.g., Fe and Al), SSA contributions largely remained &lt;1%. Our study highlights that a lack of focused measurements of TEs in SSA limits our ability to quantify this component of marine aerosol loading and the associated potential for overestimating new TE inputs from atmospheric deposition.

Analysis of Midrapidity pT Distributions of Identified Charged Particles in Pb + Pb Collisions at snn = 5.02 TeV Using Tsallis Distribution with Embedded Transverse Flow

The midrapidity transverse momentum distributions of the charged pions, kaons, protons, and antiprotons, measured by ALICE Collaboration at ten centrality classes of Pb + Pb collisions at snn = 5.02 TeV in the Large Hadron Collider (LHC, CERN, Switzerland), are successfully analyzed using combined minimum χ2 fits with a thermodynamically non-consistent, as well as thermodynamically consistent, Tsallis function with transverse flow. The extracted non-extensivity parameter q decreases systematically for all considered particle species with increasing Pb + Pb collision centrality, suggesting an increase in the degree of system thermalization with an increase in collision centrality. The results for q suggest quite a large degree of thermalization of quark–gluon plasma (QGP) created in central Pb + Pb collisions at snn = 5.02 TeV with the average number of participant nucleons ⟨Npart⟩ &gt; 160. The obtained significantly different growth rates of transverse flow velocity, ⟨βT⟩, in regions ⟨Npart⟩ &lt; 71 ± 7 and ⟨Npart⟩ &gt; 71 ± 7 with the temperature parameter T0 remaining constant within uncertainties in region ⟨Npart⟩ &gt; 71 ± 7 probably indicates that ⟨Npart⟩ ≈ 71 ± 7 (corresponding to ⟨dNch/dη⟩ ≈ 251 ± 20) is a threshold border value for a crossover transition from a dense hadronic state to the QGP phase (or mixed phase of QGP and hadrons) in Pb + Pb collisions at snn = 5.02 TeV. The threshold border value for transverse flow velocity ⟨βT⟩ ≈ 0.46 ± 0.03 (corresponding to ⟨Npart⟩ ≈ 71 ± 7), estimated by us in Pb + Pb collisions at snn = 5.02 TeV, agrees well with the corresponding border value ⟨βT⟩ ≈ 0.44 ± 0.02, recently obtained in Xe + Xe collisions at snn = 5.44 TeV, and with almost constant ⟨βT⟩ values extracted earlier in the Beam Energy Scan (BES) program of the Relativistic Heavy-Ion Collider (RHIC, Brookhaven, GA, USA) in central Au + Au collisions in the snn = 7.7 − 39 GeV energy range, where the threshold for QGP production is achieved. The correlations between extracted T0 and ⟨βT⟩ parameters are found to be greatly different in regions ⟨βT⟩ &lt; 0.46 and ⟨βT⟩ &gt; 0.46, which further supports our result obtained for the threshold border value in Pb + Pb collisions at snn = 5.02 TeV.

General balance functions of identified charged hadron pairs of (π,K,p) in Pb–Pb collisions at [formula omitted] 2.76 TeV

First measurements of balance functions (BFs) of all combinations of identified charged hadron (π,K,p) pairs in Pb–Pb collisions at sNN=2.76 TeV recorded by the ALICE detector are presented. The BF measurements are carried out as two-dimensional differential correlators versus the relative rapidity (Δy) and azimuthal angle (Δφ) of hadron pairs, and studied as a function of collision centrality. The Δφ dependence of BFs is expected to be sensitive to the light quark diffusivity in the quark–gluon plasma. While the BF azimuthal widths of all pairs substantially decrease from peripheral to central collisions, the longitudinal widths exhibit mixed behaviors: BFs of ππ and cross-species pairs narrow significantly in more central collisions, whereas those of KK and pp are found to be independent of collision centrality. This dichotomy is qualitatively consistent with the presence of strong radial flow effects and the existence of two stages of quark production in relativistic heavy-ion collisions. Finally, the first measurements of the collision centrality evolution of BF integrals are presented, with the observation that charge balancing fractions are nearly independent of collision centrality in Pb–Pb collisions. Overall, the results presented provide new and challenging constraints for theoretical models of hadron production and transport in relativistic heavy-ion collisions.

Neutral to charged kaon yield fluctuations in Pb – Pb collisions at [formula omitted] TeV

We present the first measurement of event-by-event fluctuations in the kaon sector in Pb – Pb collisions at sNN=2.76 TeV with the ALICE detector at the LHC. The robust fluctuation correlator νdyn is used to evaluate the magnitude of fluctuations of the relative yields of neutral and charged kaons, as well as the relative yields of charged kaons, as a function of collision centrality and selected kinematic ranges. While the correlator νdyn[K+,K−] exhibits a scaling approximately in inverse proportion of the charged particle multiplicity, νdyn[KS0,K±] features a significant deviation from such scaling. Within uncertainties, the value of νdyn[KS0,K±] is independent of the selected transverse momentum interval, while it exhibits a pseudorapidity dependence. The results are compared with HIJING, AMPT and EPOS–LHC predictions, and are further discussed in the context of the possible production of disoriented chiral condensates in central Pb – Pb collisions.

Systematic Study of Perovskite Layers if Doped with Strong Oxidants

Herein, strong oxidants are employed for the first time to stabilize the main frame structure of the perovskite [PbI6]4− by strengthening the interaction between the central Pb atom and coordination I atoms. A systematic study on the microstructure and macrostate of the perovskite is carried out by the synchrotron radiation technique and conventional characterization. According to the valence state and local environment of each chemical element, crystallinity and morphology of the active layer, and photoelectric properties of the solar cell, the strong oxidants, tris[2‐((1H‐pyrazol‐1‐yl)‐4‐tert‐butylpyridine)cobalt(III)tris(bis(trifluoromethylsulfonyl)imide)] (FK209) and Na2S2O8, can increase the power conversion efficiency and stability of the doped devices. A possible mechanism of doping strong oxidants is explained.

Toward a qualitative connection between the nuclear modification factors of hadrons and their quark component

In this work, we propose a method qualitatively connecting the hadron nuclear modification factor to its quark component nuclear modification factor. A parton and hadron cascade model, PACIAE, based on PYTHIA6 is then employed calculating the hadron (in final hadronic state) and its quark component (in final partonic state) nuclear modification factors in the 0%–5% most central Pb + Pb collisions at = 2.76 TeV. It turns out that the hadron nuclear modification factor is usually smaller than its quark component factor. On the other hand, the flavor (mass) ordering of the nuclear modification factor is investigated for a hadron in the final hadronic state and a quark in the final partonic state. It is found that the nuclear modification factor is more likely to be identified with the quarks and mesons but not with the baryons.

Comparison of strange particle production measurements in central Pb–Pb collisions at $$\sqrt {s_{NN} }$$ = 2.76 and 5.02 TeV by using Monte Carlo simulation models EPOS-1.99 and EPOS-LHC

Comparison of strange particle production measurements in central Pb–Pb collisions at $$\sqrt {s_{NN} }$$ = 2.76 and 5.02 TeV by using Monte Carlo simulation models EPOS-1.99 and EPOS-LHC

Study of nuclear modification factors of deuteron and anti-deuteron in Pb\u2013Pb collisions at sqrt{s_{mathrm{NN}}} =2.76,hbox {TeV}

The nuclear modification factors (R_{AA}) of d and bar{d} have been studied using the parton and hadron cascade model plus the dynamically constrained phase space coalescence model in peripheral (40–60%) and central (0–5%) Pb–Pb collisions at sqrt{s_{NN}}=2.76,hbox {TeV} with |y|<0.5, p_T<20.0 ,hbox {GeV}/hbox {c}. It is found that the R_{AA} of d, bar{d} is similar to that of hadrons (pi ^pm , p, bar{p}) and the R_{AA} of antiparticles is the same as that of particles. The suppression effect of d is more significant than that of baryons and mesons in the high-p_T region. The suppression of R_{AA} at high-p_T strongly depends on event centrality and mass of the particles, i.e., the central collision is more suppressed than the peripheral collision. Besides, the yield ratios and double ratios for different particle species, and the coalescence parameter B_2 for (d, bar{d}) in pp and Pb–Pb collisions are discussed, respectively. It is observed that the yield ratios and double ratios of d to p and p to pi are similar to those of their anti-particles in three different collision systems, suggesting that the suppressions of matter (pi ^{+}, p, d) and the corresponding antimatter (pi ^{-},bar{p},bar{d}) are around the same level.

Charged-particle multiplicity fluctuations in Pb\u2013Pb collisions at sqrt{s_{mathrm {NN}}} \xa0=\xa02.76\xa0TeV

Measurements of event-by-event fluctuations of charged-particle multiplicities in Pb–Pb collisions at sqrt{s_{mathrm {NN}}} = 2.76 TeV using the ALICE detector at the CERN Large Hadron Collider (LHC) are presented in the pseudorapidity range |eta |<0.8 and transverse momentum 0.2< p_{mathrm{T}} < 2.0 GeV/c. The amplitude of the fluctuations is expressed in terms of the variance normalized by the mean of the multiplicity distribution. The eta and p_{mathrm{T}} dependences of the fluctuations and their evolution with respect to collision centrality are investigated. The multiplicity fluctuations tend to decrease from peripheral to central collisions. The results are compared to those obtained from HIJING and AMPT Monte Carlo event generators as well as to experimental data at lower collision energies. Additionally, the measured multiplicity fluctuations are discussed in the context of the isothermal compressibility of the high-density strongly-interacting system formed in central Pb–Pb collisions.

Study of transverse momentum and nuclear modification factors distribution of charged particles produced in pp and Pb–Pb collisions at s NN = 2.76TeV and 5.02TeV

We have studied transverse momentum distributions of charged particles produced in pp and Pb–Pb collisions at [Formula: see text] TeV and 5.02 TeV in the pseudorapidity interval [Formula: see text] and transverse momentum range [Formula: see text][Formula: see text]GeV/[Formula: see text]. We simulated data using EPOS-LHC, EPOS-1.99 and QGSJETII-04 models. The simulation data is compared with the ALICE experimental data values at [Formula: see text] TeV and 5.02 TeV for pp and most central Pb–Pb collisions. It has been observed that, EPOS-LHC and QGSJETII-04 models explain the experimental results for pp collision at [Formula: see text] TeV and 5.02 TeV. The behavior of nuclear modification factors has been studied. The simulation codes of all three models EPOS-LHC, EPOS-1.99 and QGSJETII-04 overestimate the experimental results at low transverse momentum interval: [Formula: see text] GeV/[Formula: see text], for Pb–Pb collisions at [Formula: see text] TeV and 5.02 TeV. However, only EPOS-LHC model can explain the experimental data at high transverse momentum in the range: [Formula: see text] GeV/[Formula: see text]. EPOS-1.99 and QGSJETII-04 underestimate in the region of Cronin effect and cannot give satisfactory estimates for the [Formula: see text] values for which [Formula: see text] demonstrates stronger suppression because of the collective parton effect. It can be inferred that these effects are not taken into account in EPOS-1.99 and QGSJETII-04 models. These models, however, satisfactorily explain the ALICE experimental data in the ranges of [Formula: see text] for which nuclear modification factor [Formula: see text] shows rising trend.

Anisotropic fluid dynamical simulations of heavy-ion collisions

We present VAH, a (3+1)–dimensional simulation that evolves the far-from-equilibrium quark-gluon plasma produced in ultrarelativistic heavy-ion collisions with anisotropic fluid dynamics. We solve the hydrodynamic equations on an Eulerian grid using the Kurganov–Tadmor algorithm in combination with a new adaptive Runge–Kutta method. Our numerical scheme allows us to start the simulation soon after the nuclear collision, largely avoiding the need to integrate it with a separate pre-equilibrium dynamics module. We test the code's performance by simulating on the Eulerian grid conformal and non-conformal Bjorken flow as well as conformal Gubser flow, whose (0+1)–dimensional solutions are precisely known. Finally, we compare non-conformal anisotropic hydrodynamics to second-order viscous hydrodynamics in central Pb+Pb collisions and find that the former's longitudinal flow profile responds more consistently to the fluid's gradients along the spacetime rapidity direction. Program summaryManuscript Title: Anisotropic fluid dynamical simulations of heavy-ion collisionsAuthors: Mike McNelis, Dennis Bazow, Ulrich HeinzProgram Title:VAHLicensing provisions: GPLv3Programming Language: C++Computer: Laptop, desktop, clusterOperating System: GNU/Linux distributions, Mac OS XGlobal memory usage: 1.2 GB (for a 129×129×63 grid)Keywords: Ultrarelativistic heavy-ion collisions, quark-gluon plasma, relativistic hydrodynamics, computational fluid dynamicsClassification: 12 Gases and Fluids, 17 Nuclear physicsExternal routines/libraries: GNU Scientific Library (GSL)Nature of problem: Modeling the far-from-equilibrium dynamics of quark-gluon plasma produced in ultrarelativistic heavy-ion collisions.Solution method: Kurganov–Tadmor algorithm, adaptive stepsize methodRunning time: A (3+1)–d non-conformal anisotropic fluid dynamical simulation of a central Pb+Pb collision on a 129×129×63 grid takes about 530s for an Intel Xeon E5-2680 v4 multi-core processor with OpenMP acceleration (see Sec. 5.3).

Strain Induced Topological Insulator Phase in CsPbBrxI3−x (x = 0, 1, 2, and 3) Perovskite: A Theoretical Study

First-principles density functional theory was used to determine the surface band structures of CsPbBrxI3−x (x = 0, 1, 2, and 3) perovskites. The equilibrium lattice constants of CsPbBrxI3−x were obtained from the minimum of the total energy as a function of the iodine concentration. We discovered that the band gaps of CsPbBrxI3−x decreased monotonically under pressure. The phase change from a normal insulator to a topological insulator was found at approximately 2–4 GPa. The Pbp- and Brs-orbitals inverted at the R symmetric point with and without spin–orbit coupling. Nontrivial Z2 topological numbers were obtained, and the surface conduction bands were demonstrated theoretically using a 1 × 1 × 10 supercell. We ascertained that CsPbBr2I has the largest electric polarization 0.025 C/m2 under a compression strain of 10%. We also observed that in the normal insulation phase, the band gap increases with a small displacement of the central Pb atom in the z-direction, but in the topological insulator phase, the band gap decreases with the movement of the Pb atom in the z-direction. Additionally, in the supercell structure, CsPbBrxI3−x is a ferroelectric topological insulator because the Pb atom leaves its own equilibrium position.

Modified equilibrium distributions for Cooper-Frye particlization

We introduce a positive definite single-particle distribution that is suitable for describing the transition from a macroscopic hydrodynamic to a microscopic kinetic description during the late stages of heavy-ion collisions in the presence of moderately large viscous corrections. The modified equilibrium distribution function can be constructed with hydrodynamic input from either relativistic viscous fluid dynamics or anisotropic fluid dynamics. We test the modified equilibrium distribution's hydrodynamic output for a stationary hadron resonance gas subject to either shear stress, bulk pressure, or baryon diffusion current at a given freeze-out temperature and baryon chemical potential. While it does not reproduce all components of the net baryon current and energy-momentum tensor exactly, it significantly improves upon the customary linearized approximations for the non-equilibrium correction $\delta f_n$ which typically lead to unphysical negative distribution functions at large particle momenta. A comparison of particle spectra and $p_T$-differential elliptic flow coefficients from the Cooper-Frye formula computed with the modified equilibrium distribution and with linearized $\delta f_n$ corrections is presented, for two different (2+1)-dimensional hypersurfaces corresponding to central and non-central Pb+Pb collisions at the Large Hadron Collider (LHC).