Central Pb Research Articles

Crystal structure of hexa-glycinium dodeca-iodo-triplumbate.

The crystal structure of hexa-glycinium tetra-μ-iodido-octa-iodido-triplumbate, (C2H6NO2)6[Pb3I12] or (GlyH)6[Pb3I12], is reported. The compound crystallizes in the triclinic space group P. The [Pb3I12]6- anion is discrete and located around a special position: the central Pb ion located on the inversion center is holodirected, while the other two are hemidirected. The supra-molecular nature is mainly based on C-H⋯I, N-H⋯I, O-H⋯I and N-H⋯O hydrogen bonds. Dimeric cations of type (A +⋯A +) for the amino acid glycine are observed for the first time.

K*(892)± resonance production in Pb-Pb collisions at sNN=5.02 TeV

The production of K*(892)± meson resonance is measured at midrapidity (|y|<0.5) in Pb−Pb collisions at sNN=5.02 TeV using the ALICE detector at the CERN Large Hadron Collider. The resonance is reconstructed via its hadronic decay channel K*(892)±→KS0π±. The transverse momentum distributions are obtained for various centrality intervals in the pT range of 0.4−16 GeV/c. Measurements of integrated yields, mean transverse momenta, and particle yield ratios are reported and found to be consistent with previous ALICE measurements for K*(892)0 within uncertainties. The pT-integrated yield ratio 2K*(892)±/(K++K−) in central Pb−Pb collisions shows a significant suppression at a level of 9.3σ relative to pp collisions. Thermal model calculations result in an overprediction of the particle yield ratio. Although both hadron resonance gas in partial chemical equilibrium (HRG-PCE) and + simulations consider the hadronic phase, only HRG-PCE accurately represents the measurements, whereas + simulations tend to overpredict the particle yield ratio. These observations, along with the kinetic freeze-out temperatures extracted from the yields measured for light-flavored hadrons using the HRG-PCE model, indicate a finite hadronic phase lifetime, which decreases with increasing collision centrality percentile. The pT-differential yield ratios 2K*(892)±/(K++K−) and 2K*(892)±/(π++π−) are presented and compared with measurements in pp collisions at s=5.02 TeV. Both particle ratios are found to be suppressed by up to a factor of five at pT<2.0 GeV/c in central Pb−Pb collisions and are qualitatively consistent with expectations for rescattering effects in the hadronic phase. The nuclear modification factor (RAA) shows a smooth evolution with centrality and is found to be below unity at pT>8 GeV/c, consistent with measurements for other light-flavored hadrons. The smallest values are observed in most central collisions, indicating larger energy loss of partons traversing the dense medium. ©2024 CERN, for the ALICE Collaboration 2024 CERN

Skewness and kurtosis of mean transverse momentum fluctuations at the LHC energies

The first measurements of skewness and kurtosis of mean transverse momentum (〈pT〉) fluctuations are reported in Pb–Pb collisions at sNN = 5.02 TeV, Xe–Xe collisions at sNN = 5.44 TeV and pp collisions at s=5.02 TeV using the ALICE detector. The measurements are carried out as a function of system size 〈dNch/dη〉|η|<0.51/3, using charged particles with transverse momentum (pT) and pseudorapidity (η), in the range 0.2<pT<3.0 GeV/c and |η|<0.8, respectively. In Pb–Pb and Xe–Xe collisions, positive skewness is observed in the fluctuations of 〈pT〉 for all centralities, which is significantly larger than what would be expected in the scenario of independent particle emission. This positive skewness is considered a crucial consequence of the hydrodynamic evolution of the hot and dense nuclear matter created in heavy-ion collisions. Furthermore, similar observations of positive skewness for minimum bias pp collisions are also reported here. Kurtosis of 〈pT〉 fluctuations is found to be in good agreement with the kurtosis of Gaussian distribution, for most central Pb–Pb collisions. Hydrodynamic model calculations with MUSIC using Monte Carlo Glauber initial conditions are able to explain the measurements of both skewness and kurtosis qualitatively from semicentral to central collisions in Pb–Pb system. Color reconnection mechanism in PYTHIA8 model seems to play a pivotal role in capturing the qualitative behavior of the same measurements in pp collisions.

New measurements of inclusive jet suppression and jet ν2 in Pb–Pb collisions at √SNN = 5.02 TeV with ALICE

We report measurements of the inclusive charged-particle jet yield in central Pb–Pb collisions at √SNN = 5.02 TeV. Uncorrelated background is suppressed by a novel mixed-event technique, enabling extension of the jet RAA measurement down to pT = 13.5 GeV/c, with kinematic overlap with RHIC jet measurements. We also present measurements of inclusive charged-particle jet v2 in semi-central Pb–Pb collisions at √SNN = 5.02 TeV, and azimuthal dependence of jet yield suppression for event topologies selected using eventshape engineering.

SURVEY OF PB LAUSER ATHLETES' SMASH ABILITIES IN CENTRAL ACEH

Badminton is one of the most popular in Indonesia and the world. The game of badminton has basic techniques such as serves and smashes. Smash in badminton is a technique that is very necessary to get a point. This research aims to determine the smash ability of Central Aceh PB Lauser athletes. This type of research is quantitative descriptive research. The sample for this research was 5 athletes in the Men's Singles category PB Lauser Central Aceh. The research results from the five athletes had a maximum score of 35, a minimum score of 25, a mean of 29.2, and a standard deviation of 4.33. The good category is 40% and the bad category is 60%, so it can be concluded that the abilities of PB Lauser Aceh athletes are in the medium category. It is a good suggestion for the coach to provide a training program that leads to smash ability in badminton, such as training arm muscle strength.

Measurement of the radius dependence of charged-particle jet suppression in Pb–Pb collisions at [formula omitted

The ALICE Collaboration reports a differential measurement of inclusive jet suppression using pp and Pb–Pb collision data at a center-of-mass energy per nucleon–nucleon collision sNN=5.02 TeV. Charged-particle jets are reconstructed using the anti-kT algorithm with resolution parameters R=0.2, 0.3, 0.4, 0.5, and 0.6 in pp collisions and R=0.2, 0.4, 0.6 in central (0–10%), semi-central (30–50%), and peripheral (60–80%) Pb–Pb collisions. A novel approach based on machine learning is employed to mitigate the influence of jet background. This enables measurements of inclusive jet suppression in new regions of phase space, including down to the lowest jet pT≥40 GeV/c at R=0.6 in central Pb–Pb collisions. This is an important step for discriminating different models of jet quenching in the quark–gluon plasma. The transverse momentum spectra, nuclear modification factors, derived cross section, and nuclear modification factor ratios for different jet resolution parameters of charged-particle jets are presented and compared to model predictions. A mild dependence of the nuclear modification factor ratios on collision centrality and resolution parameter is observed. The results are compared to a variety of jet-quenching models with varying levels of agreement.

A Luminescent MOF Based on Pyrimidine-4,6-dicarboxylate Ligand and Lead(II) with Unprecedented Topology

In the present work, we report on a 3D MOF of {[Pb5(μ3-OH)(μ3-NO3)3(μ6-pmdc)3]·H2O}n formula (pmdc = pyrimidine-4,6-dicarboxylate) synthesized by an oven-heated, solvent-free procedure. The large connectivity afforded by the three ligands in their coordination to lead(II) ions grows cubic building units characterized by a central Pb atom with an unusual coordination index of 12 and 6 pmdc ligands occupying the faces. These cubic units are linked to one another giving rise to a quite condensed structure that represents an unprecedented topology showing the (4·62)6(43)2(45·610)3(45·68·82)6(46·69)6(612·83) point symbol. The crystalline material has been characterized by routine physico-chemical techniques to confirm its purity, and its thermal behaviour has been also studied by thermogravimetric and thermodiffractometric analyses. The solid presents a greenish blue photoluminescent emission based on pmdc ligands, as revealed by time-dependent density-functional theory (TDDFT) calculations, which is substantially more intense than in the free H2pmdc ligand according to its improved quantum yield. The emissive capacity of the material is further analysed according to decreasing temperature of the polycrystalline sample, finding that sizeable, long-lasting phosphorescence is present.

2-D polypseudo-rotaxane network in (4Z,N'Z)-N’-(amino(pyridine-2-yl)methyl)isonicotionhydrazonic (apminh) Pb(II) complex: Synthesis, structural and quantum computational studies

The crystal structure of [Pb(apminh)Cl2] has been analyzed, revealing its potential as a useful component in a storage device. The complex crystallizes in the P1¯space group and is composed of a central Pb ion coordinated with two chloride anions and a tridentate apminh organic ligand. The ligand forms two chelating rings with Pb using oxygen and nitrogen atoms, resulting in a trigonal bipyramidal geometry of the central metal ion. The crystal packing of the complex is characterized by distinct intra and intermolecular interactions, with hydrogen bond interactions playing a crucial role. The complex forms 2D polymeric chains with intermolecular π...π stacking, which are bridged by the lattice solvent (methanol) through hydrogen bonds, making the 2D chains more stable. Quantum chemical calculations suggest that the complex has high kinetic stability, low chemical reactivity, electron-donating ability, and high charge storage capacity, making it a promising component for storage devices. The electronic structure analysis demonstrates the insulating nature, stable electronic structure, and long-lasting properties of the complex, providing insights into the chemical properties of the bonding in the complex. Overall, our results highlight the potential of [Pb(apminh)Cl2] as a storage device component, although further experimentation and testing are necessary to determine its suitability for this application.

Measurement of beauty-strange meson production in Pb–Pb collisions at [formula omitted] via non-prompt [formula omitted] mesons

The production yields of non-prompt Ds+ mesons, namely Ds+ mesons from beauty-hadron decays, were measured for the first time as a function of the transverse momentum (pT) at midrapidity (|y|<0.5) in central and semi-central Pb–Pb collisions at a centre-of-mass energy per nucleon pair sNN=5.02TeV with the ALICE experiment at the LHC. The Ds+ mesons and their charge conjugates were reconstructed from the hadronic decay channel Ds+→ϕπ+, with ϕ→K−K+, in the 4<pT<36GeV/c and 2<pT<24GeV/c intervals for the 0–10% and 30–50% centrality classes, respectively. The measured yields of non-prompt Ds+ mesons are compared to those of prompt Ds+ and non-prompt D0 mesons by calculating the ratios of the production yields in Pb–Pb collisions and the nuclear modification factor RAA. The ratio between the RAA of non-prompt Ds+ and prompt Ds+ mesons, and that between the RAA of non-prompt Ds+ and non-prompt D0 mesons in central Pb–Pb collisions are found to be on average higher than unity in the 4<pT<12GeV/c interval with a statistical significance of about 1.6σ and 1.7σ, respectively. The measured RAA ratios are compared with the predictions of theoretical models of heavy-quark transport in a hydrodynamically expanding QGP that incorporate hadronisation via quark recombination.

Photoproduction of low-pT J/ψ from peripheral to central Pb–Pb collisions at 5.02 TeV

An excess of J/ψ yield at very low transverse momentum (pT<0.3 GeV/c), originating from coherent photoproduction, is observed in peripheral and semicentral hadronic Pb–Pb collisions at a center-of-mass energy per nucleon pair of sNN=5.02 TeV. The measurement is performed with the ALICE detector via the dimuon decay channel at forward rapidity (2.5<y<4). The nuclear modification factor at very low pT and the coherent photoproduction cross section are measured as a function of centrality down to the 10% most central collisions. These results extend the previous study at sNN=2.76 TeV, confirming the clear excess over hadronic production in the pT range 0−0.3 GeV/c and the centrality range 70–90%, and establishing an excess with a significance greater than 5σ also in the 50–70% and 30–50% centrality ranges. The results are compared with earlier measurements at sNN=2.76 TeV and with different theoretical predictions aiming at describing how coherent photoproduction occurs in hadronic interactions with nuclear overlap.

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

The study of the initial conditions of relativistic heavy-ion collisions and the subsequent development of hot and dense nuclear matter at the LHC is fundamental for the understanding of the strong nuclear force. The traditional approach of comparing observables with hydrodynamical models based on different initial conditions typically fails to isolate the effects of the initial conditions due to the sensitivity of the observables to the collective behaviour of the expanding system. Correlations of the mean transverse momentum [p T] and the anisotropic flow Fourier coefficients v n have been shown to serve as a unique probe of the initial conditions of the heavy-ion collisions with little to no bias from final state effects.In this talk, correlations between [p T] and v 2 or v 3 are presented as a function of centrality in Pb−Pb and Xe−Xe collisions at TeV and TeV, respectively, measured with ALICE. Additionally, measurements of the higher-order correlation between [p T], v 2, and v 3 is measured for the first time. All of these measurements are compared with hydrodynamical models using IP-Glasma or TRENTo initial conditions. The former is based on Color Glass Condensate effective theory with gluon saturation and the latter is a parameterized model with nucleons as the relevant degrees of freedom. The data is best described by models using IP-Glasma initial conditions, whereas the TRENTo based models fail to describe the data regardless of the parametrization.

Event-by-event fluctuations of mean transverse momentum in Pb–Pb and Xe–Xe collisions with ALICE

Event-by-event fluctuations of the mean transverse momentum of charged particles produced in Pb–Pb and Xe–Xe collisions at TeV and TeV, respectively, are studied as a function of the charged-particle multiplicity using the ALICE detector at the LHC. Dynamical fluctuations are observed in both collision systems which indicate correlated particle emission. The central Pb–Pb and Xe–Xe collisions show a significant reduction of the fluctuation in comparison to peripheral collisions and are in qualitative agreement with previous measurements in Pb–Pb collisions at TeV. The results are compared with the HIJING model. A clear deviation from simple superposition of independent nucleon-nucleon collisions scenario, where the final state particles are produced from superposition of particle emitting sources, is observed.

Distributions of the nuclear modification factor of pions, kaons and protons in the most central Pb–Pb collisions at $$\sqrt{{s}_{NN}}$$ = 2.76 TeV

Distributions of the nuclear modification factor of pions, kaons and protons in the most central Pb–Pb collisions at $$\sqrt{{s}_{NN}}$$ = 2.76 TeV

Two novel metal complexes based on 2,2′-bipyridine and 2,4-dihydroxybenzoic acid: Synthesis, crystal structure and catalytic performance

To further enhance the catalytic performance of copper/lead 2,4-dihydroxybenzoate salt, two novel ternary complexes, Cu(C10H8N2)2(C7H5O4)·3H2O (complex 1) and [Pb(C10H8N2)(C7H5O4)2]·H2O (complex 2) were designed by introducing carbon framework ligand. The molecular structures of complexes 1 and 2 were determined by single crystal X-ray diffraction analysis. Both complex 1 and complex 2 were crystallized in the monoclinic crystal system. The difference is that the central Cu ion in complex 1 is connected to one oxygen atom of the carboxyl group of 2,4-dihydroxybenzoic acid, while the other 2,4-dihydroxybenzoic acid anion only acts as a counterion to balance the charge. But the central Pb ion in complex 2 is connected to four oxygen atoms of the carboxyl groups of two 2,4-dihydroxybenzoic acid and forms a six-coordinated structure. The Hirshfeld surface and associated 2D fingerprint analysis offer valuable insights into the intermolecular interactions within the crystal structure. Importantly, the thermal analysis results show that the thermal decomposition temperature of complex 1 is 204.1 °C, which has better thermal stability than complex 2. Furthermore, complex 1 showed remarkable catalytic activity on RDX compared to complex 2, and changed the thermal decomposition of RDX from melting decomposition to solid phase decomposition. This study will provide a new insight into development of combustion catalysts.

Study of charged particle production at high pT using event topology in pp, p–Pb and Pb–Pb collisions at [formula omitted] TeV

This letter reports measurements which characterize the underlying event associated with hard scatterings at mid-pseudorapidity (|η|<0.8) in pp, p–Pb and Pb–Pb collisions at centre-of-mass energy per nucleon pair, sNN=5.02TeV. The measurements are performed with ALICE at the LHC. Different multiplicity classes are defined based on the event activity measured at forward rapidities. The hard scatterings are identified by the leading particle defined as the charged particle with the largest transverse momentum (pT) in the collision and having 8 <pT<15GeV/c. The pT spectra of associated particles (0.5 ≤pT<6GeV/c) are measured in different azimuthal regions defined with respect to the leading particle direction: toward, transverse, and away. The associated charged particle yields in the transverse region are subtracted from those of the away and toward regions. The remaining jet-like yields are reported as a function of the multiplicity measured in the transverse region. The measurements show a suppression of the jet-like yield in the away region and an enhancement of high-pT associated particles in the toward region in central Pb–Pb collisions, as compared to minimum-bias pp collisions. These observations are consistent with previous measurements that used two-particle correlations, and with an interpretation in terms of parton energy loss in a high-density quark gluon plasma. These yield modifications vanish in peripheral Pb–Pb collisions and are not observed in either high-multiplicity pp or p–Pb collisions.

Jet-like correlations with respect to textrm{K}^{0}_mathrm{{S}} and Lambda (overline{Lambda }) in pp and central Pb–Pb collisions at mathbf {sqrt{s_textrm{NN}}} = 5.02 TeV

Two-particle correlations with textrm{K}^{0}_mathrm{{S}}, Lambda /overline{Lambda }, and charged hadrons as trigger particles in the transverse momentum range 8{<}p_{{textrm{T}},{textrm{trig}}}{<}16 GeV/c, and associated charged particles within 1{<}p_{{textrm{T}},{textrm{assoc}}}{<}8 GeV/c, are studied at midrapidity in pp and central Pb–Pb collisions at a centre-of-mass energy per nucleon–nucleon collision sqrt{s_{textrm{NN}}}~=~5.02 TeV with the ALICE detector at the LHC. After subtracting the contributions of the flow background, the per-trigger yields are extracted on both the near and away sides, and the ratio in Pb–Pb collisions with respect to pp collisions (I_{textrm{AA}}) is computed. The per-trigger yield in Pb–Pb collisions on the away side is strongly suppressed to the level of I_{textrm{AA}}approx 0.6 for p_{{textrm{T}},{textrm{assoc}}}>3 GeV/c as expected from strong in-medium energy loss, while an enhancement develops at low p_{{textrm{T}},{textrm{assoc}}} on both the near and away sides, reaching I_{textrm{AA}}approx 1.8 and 2.7 respectively. These findings are in good agreement with previous ALICE measurements from two-particle correlations triggered by neutral pions (pi ^{0}–h) and charged hadrons (h–h) in Pb–Pb collisions at sqrt{s_{textrm{NN}}}~=~2.76 TeV. Moreover, the correlations with textrm{K}^{0}_mathrm{{S}} mesons and Lambda /overline{Lambda } baryons as trigger particles are compared to those of inclusive charged hadrons. The results are compared with the predictions of Monte Carlo models.

Measurement of the nuclear modification factor of b-jets in 5.02 TeV Pb+Pb collisions with the ATLAS detector

This paper presents a measurement of b-jet production in Pb+Pb and pp collisions at sqrt{s_{_text {NN}}}=5.02 TeV with the ATLAS detector at the LHC. The measurement uses 260 text {pb}^{-1} of pp collisions collected in 2017 and 1.4 text {nb}^{-1} of Pb+Pb collisions collected in 2018. In both collision systems, jets are reconstructed via the anti-k_{t} algorithm. The b-jets are identified from a sample of jets containing muons from the semileptonic decay of b-quarks using template fits of the muon momentum relative to the jet axis. In pp collisions, b-jets are reconstructed for radius parameters R= 0.2 and R= 0.4, and only R= 0.2 jets are used in Pb+Pb collisions. For comparison, inclusive R= 0.2 jets are also measured using 1.7 text {nb}^{-1} of Pb+Pb collisions collected in 2018 and the same pp collision data as the b-jet measurement. The nuclear modification factor, R_text {AA}, is calculated for both b-jets and inclusive jets with R= 0.2 over the transverse momentum range of 80–290 GeV. The nuclear modification factor for b-jets decreases from peripheral to central collisions. The ratio of the b-jet R_text {AA} to inclusive jet R_text {AA} is also presented and suggests that the R_text {AA} for b-jets is larger than that for inclusive jets in central Pb+Pb collisions. The measurements are compared with theoretical calculations and suggest a role for mass and colour-charge effects in partonic energy loss in heavy-ion collisions.

Hydrodynamic fluctuations and ultra-central flow puzzle in heavy-ion collisions

One of the long-standing problems in the field of high-energy heavy-ion collisions is that the dynamical models based on viscous hydrodynamics fail to describe the experimental elliptic flow v2 and the triangular flow v3 simultaneously in ultra-central collisions. The problem, known as the ultra-central flow puzzle, is specifically that hydrodynamics-based models predict the flow ratio of the two-particle cumulant method v2{2}/v3{2}>1 while v2{2}/v3{2}∼1 in the experimental data. In this Letter, we focus on the effects of hydrodynamic fluctuations during the space-time evolution of the QGP fluid on the flow observables in the ultra-central collisions. Using the (3+1)-dimensional integrated dynamical model which includes relativistic fluctuating hydrodynamics, we analyze the anisotropic flow coefficients vn{2} in 0–0.2% central Pb+Pb collisions at sNN=2.76TeV. We find that the hydrodynamic fluctuations decrease the model overestimate of v2{2}/v3{2} from the experimental data by about 19% within the present setup of η/s=1/2π. This means that the hydrodynamic fluctuations qualitatively have an effect to improve the situation for the puzzle, but the effect of the hydrodynamic fluctuations alone is quantitatively insufficient to resolve the puzzle. The decrease of the ratio largely depends on the shear viscosity η/s, which calls for future comprehensive analyses with, for example, a realistic temperature-dependent viscosity.

Measurement of substructure-dependent jet suppression in Pb+Pb collisions at 5.02 TeV with the ATLAS detector

The ATLAS detector at the Large Hadron Collider has been used to measure jet substructure modification and suppression in Pb+Pb collisions at a nucleon-nucleon center-of-mass energy $\sqrt{s_{_\mathrm{NN}}}=5.02~\mathrm{TeV}$ in comparison with $pp$ collisions at $\sqrt{s}=5.02~\mathrm{TeV}$. The Pb+Pb data, collected in 2018, have an integrated luminosity of $1.72~\mathrm{nb^{-1}}$, while the $pp$ data, collected in 2017, have an integrated luminosity of $260~\mathrm{pb}^{-1}$. Jets used in this analysis are clustered using the anti-$k_{t}$ algorithm with a radius parameter $R=0.4$. The jet constituents, defined by both tracking and calorimeter information, are used to determine the angular scale $r_\mathrm{g}$ of the first hard splitting inside the jet by reclustering them using the Cambridge-Aachen algorithm and employing the soft-drop grooming technique. The nuclear modification factor, $R_\mathrm{AA}$, used to characterize jet suppression in Pb+Pb collisions, is presented differentially in $r_\mathrm{g}$, jet transverse momentum, and in intervals of collision centrality. The $R_\mathrm{AA}$ value is observed to depend significantly on jet $r_\mathrm{g}$. Jets produced with the largest measured $r_\mathrm{g}$ are found to be twice as suppressed as those with the smallest $r_\mathrm{g}$ in central Pb+Pb collisions. The $R_\mathrm{AA}$ values do not exhibit a strong variation with jet $p_\mathrm{T}$ in any of the $r_\mathrm{g}$ intervals. The $r_\mathrm{g}$ and $p_\mathrm{T}$ dependence of jet $R_\mathrm{AA}$ is qualitatively consistent with a picture of jet quenching arising from coherence and provides the most direct evidence in support of this approach.

Search for jet quenching effects on the plain jet mass in Pb+Pb collisions at the LHC with a multiphase transport model

The plain jet mass distributions of reconstructed jets are investigated in p+p and 0–10 $$\%$$ most central Pb+Pb collisions at $$\sqrt{s_{\textrm{NN}}} = 2.76~\textrm{TeV}$$ using a dynamical multiphase transport model with a string melting mechanism. It is observed that the mean charged jet mass increases with increasing jet transverse momentum and jet radius in central Pb+Pb collisions. It is demonstrated that the plain jet mass of reconstructed partonic jet is shifted to a higher value after the evolution of partonic stage due to jet quenching in central Pb+Pb collisions. However, the jet mass shift effect is strongly weakened by non-perturbative effects from hadronization and hadronic rescatterings. This makes it difficult to observe significant hot medium modification effects on the plain jet mass distribution in the final state of relativistic heavy-ion collisions.