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Bayesian constraints on the high density QCD EoS for nuclear matter from Heavy-ion collision data
No full textA Bayesian framework is introduced to constrain the density dependence of the Equation of State (EoS) for nuclear matter. The EoS is inferred using existing measurements of elliptic flow and the mean transverse kinetic energy of protons in the beam energy range of √sNN = 2−10 GeV. Tight constraints are obtained for densities up to 4 times the nuclear saturation density. However, the results are highly sensitive to the choice of observables, highlighting the need for consistent, high-precision measurements in this energy range
Ultrafast, event-by-event heavy-ion simulations for next-generation experiments
No full textWe present a novel deep generative framework that uses probabilistic diffusion models for ultrafast, event-by-event simulations of heavy-ion collision output. This new framework is trained on ultrarelativistic quantum molecular dynamics (UrQMD) cascade data to generate a full collision event output containing 26 distinct hadron species. The output is represented as a point cloud, where each point is defined by a particle's momentum vector and its corresponding species information. Our architecture integrates a normalizing flow-based condition generator that encodes global event features into a latent vector, and a diffusion model that synthesizes a point cloud of particles based on this condition. A detailed description of the model and an in-depth analysis of its performance is provided. The conditional point-cloud diffusion model learns to generate realistic output particles of collision events which successfully reproduce the UrQMD distributions for multiplicity, momentum, and rapidity of each hadron type. The flexible point-cloud representation of the event output preserves full event-level granularity, enabling direct application to inverse problems and parameter estimation tasks while also making it easily adaptable for accelerating any event-by-event model calculation or detector simulation
FRS-R3B Software
No full textThe FRS-R3B directory within R3BRoot contains the software for the FRS (Fragment Separator) detectors that are utilized in the FRS-R3B experiments. The FRS is a pivotal instrument for investigating nuclear reactions with relativistic radioactive beams, enabling high-precision studies of exotic nuclei and nuclear structure at the limits of stability. This software is built upon the FairRoot framework, which provides the tools necessary for both Monte Carlo simulations and data analysis of experimental results. The R3B experimental program is part of the broader nuclear physics research efforts at the FAIR (Facility for Antiproton and Ion Research), a cutting-edge international research facility that utilizes heavy-ion and antiproton beams to explore fundamental questions in nuclear physics, with a particular focus on the production and behavior of rare isotopes under extreme conditions. The FRS-R3B software package is a source distribution with recurring releases for MacOS and Linux
Study on the equation-of-state with light clusters and hypernuclei
No full textHeavy-ion collision experiments offer a unique opportunity to explore the early stages of the Universe by creating matter under extreme conditions of high temperature and baryon density. The properties of such matter are governed by the equation-of-state (EoS), which remains a central focus of investigation from both experimental and theoretical perspectives. Flow harmonics are among the most sensitive observables for probing the EoS, as they strongly reflect the underlying interactions and degrees of freedom of the system. In this article, we review the current status of our understanding of the EoS based on microscopic transport models, emphasizing comparisons with experimental data in the few GeV energy range
Common femtoscopic hadron-emission source in pp collisions at the LHC
No full textThe femtoscopic study of pairs of identical pions is particularly suited to investigate the effective source function of particle emission, due to the resulting Bose–Einstein correlation signal. In small collision systems at the LHC, pp in particular, the majority of the pions are produced in resonance decays, which significantly affect the profile and size of the source. In this work, we explicitly model this effect in order to extract the primordial source in pp collisions at TeV from charged – correlations measured by ALICE. We demonstrate that the assumption of a Gaussian primordial source is compatible with the data and that the effective source, resulting from modifications due to resonances, is approximately exponential, as found in previous measurements at the LHC. The universality of hadron emission in pp collisions is further investigated by applying the same methodology to characterize the primordial source of – pairs. The size of the primordial source is evaluated as a function of the transverse mass () of the pairs, leading to the observation of a common scaling for both – and – , suggesting a collective effect. Further, the present results are compatible with the scaling of the – and p primordial source measured by ALICE in high multiplicity pp collisions, providing additional evidence for the presence of a common emission source for all hadrons in small collision systems at the LHC. This will allow the determination of the source function for any hadron–hadron pairs with high precision, granting access to the properties of the possible final-state interaction among pairs of less abundantly produced hadrons, such as strange or charmed particles
Multiplicity dependence of and production in pp collisions at TeV
No full textThe first measurement at midrapidity (|y|< 0.5) of the production yield of the strange-charm baryons and as a function of transverse momentum (p) in different charged-particle multiplicity classes in proton-proton collisions at TeV with the ALICE experiment at the LHC is reported. The baryon is reconstructed via the decay channel in the range 4 < p< 12 GeV/c, while the baryon is reconstructed via both the and decay channels in the range 2 < p< 12 GeV/c. The baryon-to-meson and the baryon-to-baryon production yield ratios show no significant dependence on multiplicity. In addition, the observed yield ratios are not described by theoretical predictions that model charm-quark fragmentation based on measurements at ee and ep colliders, indicating differences in the charm-baryon production mechanism in pp collisions. A comparison with different event generators and tunings, including different modelling of the hadronisation process, is also discussed. Moreover, the branching-fraction ratio of is measured as 0.825 ± 0.094 (stat.) ± 0.081 (syst.). This value supersedes the previous ALICE measurement, improving the statistical precision by a factor of 1.6.[graphic not available: see fulltext
Particle production as a function of charged-particle flattenicity in pp collisions at = 13 TeV
No full textThis paper reports the first measurement of the transverse momentum () spectra of primary charged pions, kaons, (anti)protons, and unidentified particles as a function of the charged-particle flattenicity in pp collisions at = 13 TeV. Flattenicity is a novel event shape observable that is measured in the pseudorapidity intervals covered by the V0 detector, 2.8 < η < 5.1 and -3.7 < η < -1.7. According to QCD-inspired phenomenological models, it shows sensitivity to multiparton interactions and is less affected by biases toward larger due to local multiplicity fluctuations in the V0 acceptance than multiplicity. The analysis is performed in minimum-bias (MB) as well as in high-multiplicity events up to = 20 GeV/c. The event selection requires at least one charged particle produced in the pseudorapidity interval |η| < 1. The measured pT distributions, average pT, kaon-to-pion and proton-to-pion particle ratios, presented in this paper, are compared to model calculations using pythia 8 based on color strings and EPOS LHC. The modification of the -spectral shapes in low-flattenicity events that have large event activity with respect to those measured in MB events develops a pronounced peak at intermediate (2 < < 8 GeV/c), and approaches the vicinity of unity at higher . The results are qualitatively described by pythia, and they show different behavior than those measured as a function of charged-particle multiplicity based on the V0M estimator
Femtoscopic study of the proton-proton and proton-deuteron systems in heavy-ion collisions at the LHC
No full textThis work reports femtoscopic correlations of −(−) and −(-) pairs measured in Pb–Pb collisions at center-of-mass energy per nucleon = 5.02 TeV in the ALICE Collaboration. A fit to the measured proton-proton correlation functions allows one to extract the dependence of the nucleon femtoscopic radius of the particle-emitting source on the pair transverse mass () and on the average charge particle multiplicity 〈/dη for three centrality intervals (0–10%,10−−30%,30−−50%). In both cases, the expected power-law and linear scalings are observed, respectively. The measured p–d correlations can be described by both two- and three-body calculations, indicating that the femtoscopy observable is not sensitive to the short-distance features of the dynamics of the p-(p-n) system, due to the large inter-particle distances in Pb–Pb collisions at the LHC. Indeed, in this study, the minimum measured femtoscopic source sizes for protons and deuterons have a minimum value at 2.73 and 3.10 fm, respectively, for the 30–50% centrality collisions. Moreover, the -scaling obtained for the p–p and p–d systems is compatible within 1σ of the uncertainties. These findings provide new input for fundamental studies on the production of light (anti)nuclei under extreme conditions
