Collision Systems Research Articles

Isoscaling properties for neutron-rich fragments in highly asymmetric heavy ion collision systems* *Supported by the National Natural Science Foundation of China (12375123, 11975091) and the Program for Innovative Research Team (in Science and Technology) in University of Henan Province (21IRTSTHN011), China

Traditionally, isoscaling has been interpreted and applied within the framework of the grand canonical ensemble, based on the assumption that fragment production occurs following the attainment of a statistical equilibrium state. However, the influence of the symmetry energy can lead to differences in the neutron and density distribution in neutron-rich nuclei. This in turn may impact the isoscaling parameters (usually denoted by α and β). We examine the isoscaling properties for neutron-rich fragments produced in highly asymmetric systems on inverse kinematics, namely Ca and Ni + Be at 140 MeV per nucleon. We evaluate α and β values and sort them as a function of the neutron excess . The significant differences in α extracted from fragments within different ranges of I emphasize the importance of understanding the dependence of isoscaling parameters on fragments generated in various collision regions. Furthermore, the value for a specific fragment in small size and highly isospin asymmetry systems can serve as a probe to detect the variations in neutron density and proton density in different regions of the nucleus and indicate the limitations of theoretical models in investigating these issues.

The functional generalization of the Boltzmann-Vlasov equation and its gauge-like symmetry

We argue that one can model deviations from the ensemble average in non-equilibrium statistical mechanics by promoting the Boltzmann equation to an equation in terms of functionals , representing possible candidates for phase space distributions inferred from a finite observed number of degrees of freedom. We find that, provided the collision term and the Vlasov drift term are both included, a gauge-like redundancy arises which does not go away even if the functional is narrow. We argue that this effect is linked to the gauge-like symmetry found in relativistic hydrodynamics [Ann. Phys. 442, 168902 (2022)] and that it could be part of the explanation for the apparent fluid-like behavior in small systems in hadronic collisions and other strongly-coupled small systems [Annu. Rev. Nucl. Part. Sci. 68, 211 (2018)]. When causality and Lorentz invariance are omitted this problem can be look at via random matrix theory show, and we show that in such a case thermalization happens much more quickly than the Boltzmann equation would infer. We also sketch an algorithm to study this problem numerically.

Early Cretaceous magmatism archives crustal architecture of northern Lhasa Terrane, central Tibetan Plateau

Identification of continental crustal architecture in orogenic belts is essential for understanding the geodynamic evolution of global continental collision systems. However, ongoing debates surrounding the crustal nature of the Lhasa Terrane in the central Tibetan Plateau impede our comprehension of its tectonic evolution. Mesozoic intermediate-felsic magmatism in the Lhasa Terrane offers key insights into the crustal architecture before the India-Asia collision. Here we report zircon U-Pb-Hf isotope, whole-rock element and SrNd isotope data from Early Cretaceous granitoids in the Baingoin batholith, northern Lhasa Terrane. These granitoids (127–115 Ma) exhibit variable SiO2 (62.99–73.86 wt%), K2O (1.15–4.74 wt%), and MgO (0.49–2.48 wt%) contents. They are classified as low- to high-K calc-alkaline and metaluminous to peraluminous series, enriched in large ion lithophile elements (e.g., Rb) and light rare earth elements ((La/Yb)N = 7.08–18.3), and depleted in high field strength elements (e.g., Nb, Ta, and Ti). These granitoids display geochemical affinities with I-type granitoid rocks and can be further subdivided into three groups. Group 1 granitoids exhibit the highest zircon εHf(t) (−1.57 to 5.85) and whole-rock εNd(t) (−3.37 to −2.45), and lowest (87Sr/86Sr)i (0.706018 to 0.706922) values, whereas Group 2 granitoids have wide ranges of zircon Hf (εHf(t) = −7.78 to 2.26) and enriched whole-rock SrNd isotope compositions ((87Sr/86Sr)i = 0.707214 to 0.707918; εNd(t) = −7.38 to −6.14). These suggest that Group 1 and Group 2 granitoids may be dominantly derived from the juvenile and ancient crustal sources, respectively. Group 3 granitoids are characterized by zircon Hf (εHf(t) = −2.85 to 3.52) and whole-rock SrNd isotope compositions ((87Sr/86Sr)i = 0.706473 to 0.707692; εNd(t) = −4.50 to −3.01) falling between the ranges of the previous two groups, likely represent a mixture of juvenile crustal-derived melt with 10–15% of reworked ancient crustal materials. Integrating previous research, we propose that the persistent ancient crustal basement beneath the northern Lhasa Terrane was concurrently undergoing significant modification through juvenile crustal materials during the Early Cretaceous. These Early Cretaceous Baingoin batholith preserves crucial records of crustal evolution and highlights the influence of upwelling asthenosphere during the transition from Bangong-Nujiang oceanic subduction to Lhasa-Qiangtang collision.

Multi-charmed and singled charmed hadrons from coalescence: yields and ratios in different collision systems at LHC

We study the production of charmed and multi-charmed hadrons in ultra-relativistic Heavy Ion Collisions coupling the transport approach for charm dynamics in the medium to an hybrid hadronization model of coalescence plus fragmentation. In this paper, we mainly discuss the particle yields for single charmed and multi-charmed baryons focusing mainly on the production of Ξcc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Xi _{cc}$$\\end{document} and Ωccc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Omega _{ccc}$$\\end{document}. We provide first predictions for PbPb collision in 0-10%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$0 \\! - \\! 10\\%\\ $$\\end{document}centrality class and then we explore the system size dependence through KrKr , to ArAr and OO collisions, planned within the ALICE3 experiment. In these cases, a monotonic behavior for the yields emerges which can be tested in future experimental data. We found about three order of magnitude increase in the production of Ωccc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Omega _{ccc}$$\\end{document} in PbPb collisions compared with the yield in small collision systems like OO collisions. Furthermore, we investigate the effects on the Ωccc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Omega _{ccc}$$\\end{document} particle yield and spectra coming from the modification of the charm quark distribution due to the different size of the collision systems also comparing it to the case of thermalized charm distributions. These results suggest that observation on the Ωccc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Omega _{ccc}$$\\end{document} spectra and their evolution across system size can give novel information about the partial thermalization of the charm quark distribution as well as to its wave function width. Furthermore, we find that the Ωccc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Omega _{ccc}$$\\end{document} /D0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D^0$$\\end{document} ratio is an observable more sensitive with respect to Λc\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\Lambda _c$$\\end{document} /D0\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$D^0$$\\end{document} , this ratio is predicted to span over two order of magnitude from large to small systems.

Recent Findings from Heavy-Flavor Angular Correlation Measurements in Hadronic Collisions

The study of angular correlations of heavy-flavor particles in hadronic collisions can provide crucial insight into the heavy quark production, showering, and hadronization processes. The comparison with model predictions allows us to discriminate among different approaches for heavy quark production and hadronization, as well as different treatments of the underlying event employed by the models to reproduce correlation observables. In ultra-relativistic heavy-ion collisions, where a deconfined state of matter, the quark–gluon plasma (QGP), is created, heavy-flavor correlations can shed light on the modification of the heavy quark fragmentation due to the interaction between charm and beauty quarks with the QGP constituents, as well as characterize their energy loss processes while traversing the medium. Insight into the possible emergence of collective-like mechanisms in smaller systems, resembling those observed in heavy-ion collisions, can also be obtained by performing correlation studies in high-multiplicity proton–proton and proton–nucleus collisions. In this review, the most recent and relevant measurements of heavy-flavor correlations performed in all collision systems at the LHC and RHIC will be presented, and the new understandings that they provide will be discussed.

Observation of the Electromagnetic Field Effect via Charge-Dependent Directed Flow in Heavy-Ion Collisions at the Relativistic Heavy Ion Collider

The deconfined quark-gluon plasma (QGP) created in relativistic heavy-ion collisions enables the exploration of the fundamental properties of matter under extreme conditions. Noncentral collisions can produce strong magnetic fields on the order of 1018 G, which offers a probe into the electrical conductivity of the QGP. In particular, quarks and antiquarks carry opposite charges and receive contrary electromagnetic forces that alter their momenta. This phenomenon can be manifested in the collective motion of final-state particles, specifically in the rapidity-odd directed flow, denoted as v1(y). Here, we present the charge-dependent measurements of dv1/dy near midrapidities for π±, K±, and p(p¯) in Au+Au and isobar (Ru4496+Ru4496 and Zr4096+Zr4096) collisions at sNN=200 GeV, and in Au+Au collisions at 27 GeV, recorded by the STAR detector at the Relativistic Heavy Ion Collider. The combined dependence of the v1 signal on collision system, particle species, and collision centrality can be qualitatively and semiquantitatively understood as several effects on constituent quarks. While the results in central events can be explained by the u and d quarks transported from initial-state nuclei, those in peripheral events reveal the impacts of the electromagnetic field on the QGP. Our data put valuable constraints on the electrical conductivity of the QGP in theoretical calculations. Published by the American Physical Society 2024

Calculation of momentum correlation functions between π, K , and p for several heavy-ion collision systems at sNN=39 GeV

Momentum correlation functions between π, K, and p are calculated for several heavy-ion collision systems, namely B510+B510, O816+O816, Ca2040+Ca2040, and Au79197+Au79197 in central collisions as well as Au79197+Au79197 collision in different centralities at center-of-mass energy sNN=39 GeV within the framework of a multiphase transport model complemented by the Lednický and Lyuboshitz analytical method. The results present the centrality and system-size dependence of the momentum correlation functions among pairs of π, K, and p, from which the emission source-size can be deduced. It is found that the deduced source sizes increase with the decreasing of centrality for Au + Au system or with the increasing of system size in central collisions with different nuclear size. In addition, through the momentum correlation functions of nonidentical particle pairs gated on velocity, the average emission sequence of nonidentical particles can be indicated. The results illustrate that in the small relative momentum region, protons are emitted in average earlier than π+ and K+, and K+ are emitted averagely earlier than π+. Furthermore, it seems that larger interval of the average emission order among them is exhibited for smaller collision systems. The present study sheds light on the dynamics of light particle emission at RHIC energy. Published by the American Physical Society 2024

Analysis of discontinuous dynamical behaviors for a 3-DOF friction collision system with dynamic vibration absorber

Analysis of discontinuous dynamical behaviors for a 3-DOF friction collision system with dynamic vibration absorber

Exploring anisotropic flow via the Boltzmann transport equation employing the Tsallis blast wave description at LHC energies

Anisotropic flows i.e. azimuthal anisotropies in the particle production are one of the important probes in characterizing the properties of the strongly interacting matter created in the relativistic heavy-ion collisions. These observables are sensitive to both the transport properties as well as the equation of state of the quantum chromodynamics matter. We have adopted the Boltzmann transport equation (BTE) in the relaxation time approximation to describe the experimental data for harmonic flows such as elliptic flow (v 2), triangular flow (v 3), quadrangular flow (v 4) obtained in heavy-ion collisions at large hadron collider (LHC) energies. In this analysis, we have used Tsallis statistics as an initial distribution and the Tsallis blast wave description is used as the equilibrium distribution function while describing the evolution of the particle production in BTE. We have fitted the transverse momentum spectra, v 2, v 3, and v 4 of identified hadrons such as pion, kaon, and proton for Pb–Pb and Xe–Xe collisions at the LHC energies of sNN = 5.02 TeV and sNN = 5.44 TeV, respectively for various centralities. Our study offers the comparative analysis between the two distinct collision systems operating at comparable collision energies. The present formulation successfully fits the experimental data for p T - spectra upto p T = 8 GeV and effectively explains the anisotropic flows data upto p T = 10 GeV with a very favourable χ 2/ndf. We observe that the average transverse flow velocity (〈β〉) and the kinetic freeze-out temperature (T) extracted in our analysis decrease as we go towards the peripheral collisions. Non-extensive parameters (q AA and q pp ) exhibit an ascending trend from central to peripheral collisions, signifying an almost thermalized system in the most central collisions and a non-equilibrium state in peripheral ones. The azimuthal modulation amplitudes (ρ a ) for v 2, v 3, and v 4 exhibit an increasing pattern as one moves from the most central to peripheral collisions in both the Pb–Pb and Xe–Xe nuclei interactions.

Measurements of long-range two-particle correlation over a wide pseudorapidity range in p–Pb collisions at sNN\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s_{\ extrm{NN}}} $$\\end{document} = 5.02 TeV

Correlations in azimuthal angle extending over a long range in pseudorapidity between particles, usually called the “ridge” phenomenon, were discovered in heavy-ion collisions, and later found in pp and p–Pb collisions. In large systems, they are thought to arise from the expansion (collective flow) of the produced particles. Extending these measurements over a wider range in pseudorapidity and final-state particle multiplicity is important to understand better the origin of these long-range correlations in small collision systems. In this Letter, measurements of the long-range correlations in p–Pb collisions at sNN\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s_{\ extrm{NN}}} $$\\end{document} = 5.02 TeV are extended to a pseudorapidity gap of ∆η ~ 8 between particles using the ALICE forward multiplicity detectors. After suppressing non-flow correlations, e.g., from jet and resonance decays, the ridge structure is observed to persist up to a very large gap of ∆η ~ 8 for the first time in p–Pb collisions. This shows that the collective flow-like correlations extend over an extensive pseudorapidity range also in small collision systems such as p–Pb collisions. The pseudorapidity dependence of the second-order anisotropic flow coefficient, v2(η), is extracted from the long-range correlations. The v2(η) results are presented for a wide pseudorapidity range of –3.1 < η < 4.8 in various centrality classes in p–Pb collisions. To gain a comprehensive understanding of the source of anisotropic flow in small collision systems, the v2(η) measurements are compared with hydrodynamic and transport model calculations. The comparison suggests that the final-state interactions play a dominant role in developing the anisotropic flow in small collision systems.

Multiplicity Dependence of Quarkonium Production

Recent measurements on heavy-flavour production as a function of charged-particle multiplicity at the LHC are discussed. Focus is given to quarkonium results in small (pp or pPb) collision systems. The measurements of relative yields, i.e., the ratio of the particle yields in given multiplicity intervals to the multiplicity integrated yield are presented and compared to model calculations from Monte Carlo event generators as well as to models considering effects at play in the initial and/or final state of the collision. The absolute inclusive J/ψ yield as a function of the absolute charged-particle multiplicity is evaluated; a smooth behaviour of the absolute yield is observed across collision systems, from pp to pPb and PbPb collisions. Analogous measurements of the excited-to-ground state quarkonium ratios as a function of charged-particle multiplicity are also reviewed. Finally, the study of exotic particle production as a function of charged-particle multiplicity is introduced as a complementary tool to investigate the nature of the χc1(3872) hadron.

System-size dependence of the hadronic rescattering effect at energies available at the CERN Large Hadron Collider

The first measurements of K*(892)0 resonance production as a function of charged-particle multiplicity in Xe-Xe collisions at sNN=5.44 TeV and pp collisions ats=5.02 TeV using the ALICE detector are presented. The resonance is reconstructed at midrapidity (|y| &lt; 0.5) using the hadronic decay channel K*0 →K±π∓. Measurements of transverse-momentum integrated yield, mean transverse-momentum, nuclear modification factor of K*0, and yield ratios of resonance to stable hadron (K*0/K) are compared across different collision systems (pp, p-Pb, Xe-Xe, and Pb-Pb) at similar collision energies to investigate how the production of K*0 resonances depends on the size of the system formed in these collisions. The hadronic rescattering effect is found to be independent of the size of colliding systems and mainly driven by the produced charged-particle multiplicity, which is a proxy of the volume of produced matter at the chemical freeze-out. In addition, the production yields of K*0 in Xe-Xe collisions are utilized to constrain the dependence of the kinetic freeze-out temperature on the system size using the hadron resonance gas–partial chemical equilibrium model. ©2024 CERN, for the ALICE Collaboration 2024 CERN

Observing quantum matter-wave diffraction in the energetic He2+-He collisions

We present an experiment combined with numerical simulations to study single and double electron capture processes induced during the collisions between the He target and the He2+ projectile in the energy range 2–20 keV/u. According to our experimental observations, measuring the angular distribution of the scattered projectile He2+ reveals a clear oscillatory structure. The latter records an imprint of the collision dynamics, specifically, a signature of the matter-wave scattering and the internal electronic structure of the collisional system He2+-He. We found that this feature is sensitive to the incident projectile's energy and the nature of the involved process. With the help of four-body semiclassical close coupling and classical trajectory Monte Carlo methods, we show that the observed structure is of a quantum nature. This is further supported by a simple mathematical model based on Fraunhofer-type diffraction of light, to which the oscillations are attributed. Our findings thus provide insights into the role of quantum phenomena in characterizing collision dynamics. Published by the American Physical Society 2024

Particle Production in pA Collisions at Mid-Rapidity in the Color Glass Condensate

Particle correlations in small collisions systems, like proton–nucleus, lie at the core of the discussion about whether quark–gluon plasma is produced in small systems. Both initial and final state explanations have been essayed to describe such correlations. In this work, we focus on the initial state explanations provided by the quantum effects in the initial wave function of the incoming hadrons, in the framework of the Color Glass Condensate effective theory. We describe the formalism indicating the different inputs required for phenomenological applications. We compare the results from two different models, finding that the results for azimuthal harmonics agree qualitatively, but show quantitative differences, particularly at transverse momenta above the saturation scale.

String Interactions as a Source of Collective Behaviour

The discovery of collective effects in small collision systems has spurred a renewed interest in hadronization models, and is also a source for collective effects all the way to large collision systems, where they are usually ascribed to the creation of a Quark–Gluon Plasma. In this topical mini-review, the microscopic model for string interactions, based on the Lund string hadronization model, developed with exactly this aim in mind is reviewed, and some prospects for the future are presented.

Charged-particle production as a function of the relative transverse activity classifier in pp, p–Pb, and Pb–Pb collisions at the LHC

Measurements of charged-particle production in pp, p–Pb, and Pb–Pb collisions in the toward, away, and transverse regions with the ALICE detector are discussed. These regions are defined event-by-event relative to the azimuthal direction of the charged trigger particle, which is the reconstructed particle with the largest transverse momentum pTtrig\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\left({p}_{\ extrm{T}}^{\ extrm{trig}}\\right) $$\\end{document} in the range 8 <pTtrig\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {p}_{\ extrm{T}}^{\ extrm{trig}} $$\\end{document}< 15 GeV/c. The toward and away regions contain the primary and recoil jets, respectively; both regions are accompanied by the underlying event (UE). In contrast, the transverse region perpendicular to the direction of the trigger particle is dominated by the so-called UE dynamics, and includes also contributions from initial- and final-state radiation. The relative transverse activity classifier, RT=NchT/NchT\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {R}_{\ extrm{T}}={N}_{\ extrm{ch}}^{\ extrm{T}}/\\left\\langle {N}_{\ extrm{ch}}^{\ extrm{T}}\\right\\rangle $$\\end{document}, is used to group events according to their UE activity, where NchT\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {N}_{\ extrm{ch}}^{\ extrm{T}} $$\\end{document} is the charged-particle multiplicity per event in the transverse region and NchT\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\left\\langle {N}_{\ extrm{ch}}^{\ extrm{T}}\\right\\rangle $$\\end{document} is the mean value over the whole analysed sample. The energy dependence of the RT distributions in pp collisions at s\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s} $$\\end{document} = 2.76, 5.02, 7, and 13 TeV is reported, exploring the Koba-Nielsen-Olesen (KNO) scaling properties of the multiplicity distributions. The first measurements of charged-particle pT spectra as a function of RT in the three azimuthal regions in pp, p–Pb, and Pb–Pb collisions at sNN\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\sqrt{s_{\ extrm{NN}}} $$\\end{document} = 5.02 TeV are also reported. Data are compared with predictions obtained from the event generators PYTHIA 8 and EPOS LHC. This set of measurements is expected to contribute to the understanding of the origin of collective-like effects in small collision systems (pp and p–Pb).

Modeling, driving characterization of collision and stick-slip vibration-driven system

Abstract Considering the internal collision vibration-driven and external discontinuous resistance tolerance fusion conditions, the non-smooth dynamics characteristics of collision and stick-slip vibration-driven system are studied and experimented. Unilateral collision behavior of internal oscillators under the action of a periodic force to achieve system motion in different directions, it overcome the external Coulomb friction force and drives the system to drive in steady state under a certain direction. The kinematic and dynamic models of the system are established, and the collision and stick-slip driving motion of the system is analyzed based on the theory of non-smooth dynamics. The voice coil motor is used as the internal driving element, and the vibration driving test platform is designed and fabricated, and the driving characteristics of the system are studied experimentally. The study shows that there are three forms of movement in the steady state driving motion of the system: sticking motion, forward motion and backward motion; sine wave excitation and triangular wave excitation as input excitation have the characteristic of smoother operation with less shock; external excitation parameter regulation can change the system speed and direction of the movement; excitation frequency as a regulation parameter has the advantages of speed bandwidth, continuity, and so on; the system average driving speed in the numerical simulation and experimental test with the system average driving speed in numerical simulation and experimental test has the same rule of change, the backward motion is located in the low-frequency region, the forward motion is located in the high-frequency region, the friction coefficient and the excitation amplitude affect the size of driving speed. The results and methods of this study provide a corresponding theoretical basis for the design and parameter optimization of vibration-driven robots.

Modified Complex Robert-Bonamy calculations of line shape parameters for the CO2-H2O collision system

Modified Complex Robert-Bonamy calculations were made for the CO2-H2O collision system using an intermolecular potential comprised of quadrupole-dipole, quadrupole-quadrupole, Lennard-Jones atom-atom, induction, and London dispersion terms. The initial atom-atom parameters were obtained using combination rules and the other parameters from taken from the literature. The intermolecular potential was then adjusted to give results that agree with the measurements of Sung et al. [Can. J. Phys. 87,469-484, 2009]. The final potential results (pot 46) compared with the data of Sung et al. have an average percent difference of 0.07 and a standard deviation of 1.096 %. Calculations were then made for all transitions in the 00011-00001 band with J” from 0 to 120 at 13 temperatures from 200 to 3000 K. The speed dependence of the half-width and line shift were computed for use in more advanced line shape models. The temperature dependence of the half-widths and line shifts were determined using the double power-law (DPL) model of Gamache and Vispoel [JQSRT 217, 440-452, 2018].

Photon-triggered jets as probes of multi-stage jet modification

Prompt photons are created in the early stages of heavy ion collisions and traverse the QGP medium without any interaction. Therefore, photontriggered jets can be used to study the jet quenching in the QGP medium. In this work, photon-triggered jets are studied through different jet and jet substructure observables for different collision systems and energies using the JETSCAPE framework. Since the multistage evolution used in the JETSCAPE framework is adequate to describe a wide range of experimental observables simultaneously using the same parameter tune, we use the same parameters tuned for jet and leading hadron studies. The same isolation criteria used in the experimental analysis are used to identify prompt photons for better comparison. For the first time, high-accuracy JETSCAPE results are compared with multi-energy LHC and RHIC measurements to better understand the deviations observed in prior studies. This study highlights the importance of multistage evolution for the simultaneous description of experimental observables through different collision systems and energies using a single parameter tune.

Latest ALICE results on charm and beauty hadronisation in hadronic collisions

The study of heavy-flavour mesons and baryons in hadronic collisions provides unique access to the properties of heavy-quark hadronisation in the presence of large partonic densities, where new mechanisms of hadron formation beyond in-vacuum fragmentation can emerge. Performing these measurements in intervals of charged-particle multiplicities across different collision systems provides sensitivity to understand whether different hadronisation mechanisms are at play in small and large hadronic colliding systems. In this contribution, a selection of the latest charm and beauty production measurements in proton–proton (pp) collisions is presented, which can shed light on the modification of the heavy-quark hadronisation mechanisms with respect to leptonic collisions. New published results of the production of all prompt charm ground states in pp collisions at √S = 13 TeV, which allowed us to measure the charm fragmentation fractions and the total cc production cross section at midrapidity, will be shown. The new final measurement of non-prompt (i.e. originating from beauty-hadron decays) Λc+ baryons in the same collisions system will be discussed to provide a quantitative comparison between the hadronisation properties of beauty and charm hadrons. New measurements of Ξc0 production as a function of charged-particle multiplicity in pp collisions at √S = 13, and of Ξc0 production in p–Pb collisions at √SNN = 5.02 TeV, will be also presented, shedding further light on the hadronisation of charm-strange baryons in different colliding systems.