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Search for quasi-particle scattering in the quark-gluon plasma with jet splittings in pp and PbPb collisions at = 5.02 TeV
No full textThe ALICE Collaboration reports measurements of the large relative transverse momentum () component of jet substructure in pp and Pb-Pb collisions at center-of-mass energy per nucleon pair =5.02 TeV. Enhancement in the yield of such large-() emissions in head-on Pb-Pb collisions is predicted to arise from partonic scattering with quasiparticles of the quark-gluon plasma. The analysis utilizes charged-particle jets reconstructed by the anti-() algorithm with resolution parameter R=0.2 in the transverse-momentum interval 60 < < 80 GeV/c. The soft drop and dynamical grooming algorithms are used to identify high transverse momentum splittings in the jet shower. Comparison of measurements in Pb-Pb and pp collisions shows medium-induced narrowing, corresponding to yield suppression of high-() splittings, in contrast to the expectation of yield enhancement due to quasiparticle scattering. The measurements are compared to theoretical model calculations incorporating jet modification due to jet-medium interactions (“jet quenching”), both with and without quasiparticle scattering effects. These measurements provide new insight into the underlying mechanisms and theoretical modeling of jet quenching
J/ψ-hadron correlations at midrapidity in pp collisions at = 13 TeV
No full textWe report on the measurement of inclusive, non-prompt, and prompt J/ψ-hadron correlations by the ALICE Collaboration at the CERN Large Hadron Collider in pp collisions at a center-of-mass energy of 13 TeV. The correlations are studied at midrapidity (|y| < 0.9) in the transverse momentum ranges p < 40 GeV/ c for the J/ψ and 0.15 < p< 10 GeV/c and |η| < 0.9 for the associated hadrons. The measurement is based on minimum bias and high multiplicity data samples corresponding to integrated luminosities of L = 34 nb and L = 6.9 pb, respectively. In addition, two more data samples are employed, requiring, on top of the minimum bias condition, a threshold on the tower energy of E = 4 and 9 GeV in the ALICE electromagnetic calorimeters, which correspond to integrated luminosities of L = 0.9 pb and L = 8.4 pb, respectively. The azimuthally integrated near and away side yields of associated charged hadrons per J/ψ trigger are presented as a function of the J/ψ and associated hadron transverse momentum. The measurements are discussed in comparison to PYTHIA calculations
J/-hadron correlations at midrapidity in pp collisions at = 13 TeV
No full textNo data abstract available
Higher-order symmetry plane correlations in Pb-Pb collisions at = 5.02TeV
No full textThe correlations between event-by-event fluctuations of symmetry planes are measured in Pb-Pb collisions at a center-of-mass energy per nucleon pair = 5.02TeV recorded by the ALICE detector at the Large Hadron Collider. This analysis is conducted using the Gaussian estimator technique, which is insensitive to biases from correlations between different flow amplitudes. The study presents, for the first time, the centrality dependence of correlations involving up to five different symmetry planes. The correlation strength varies depending on the harmonic order of the symmetry plane and the collision centrality. Comparisons with measurements from lower energies indicate no significant differences within uncertainties. Additionally, the results are compared with hydrodynamic model calculations. Although the model predictions provide a qualitative explanation of the experimental results, they overestimate the data for some observables. This is particularly true for correlators that are sensitive to the nonlinear response of the medium to initial-state anisotropies in the collision system. As these new correlators provide unique information—independent of flow amplitudes—their usage in future model developments can further constrain the properties of the strongly interacting matter created in ultrarelativistic heavy-ion collisions
Toward a topological data analysis for heavy-ion collisions
No full textThe collective expansion of the quark-gluon plasma (QGP) created in heavy-ion collisions suggests that geometry-inspired approaches can be useful in extracting information about the QGP. In this work, a systematic study of observables based on topological data analysis is provided for simulations of heavy-ion collisions. Specifically, we implement persistent homology observables for metric-based complexes in the heavy-ion model TRAJECTUM and provide predictions for Pb-Pb and O-O collisions, where the tunable model parameters are taken from a Bayesian analysis performed in Pb-Pb collisions. This, in particular, allows us to compute systematic uncertainties on our observables from the uncertainties in the model parameters. To bridge between new and already established observables, we build a dictionary linking the topological observables to traditional ones, such as particle multiplicities, momentum distributions, and the elliptic flow coefficient. While the persistent homology observables largely reflect known phenomenology and do not show enhanced sensitivity to the model’s tunable parameters compared to conventional observables, this study demonstrates the viability and robustness of topological techniques in the context of heavy-ion physics. They may offer alternative perspectives and potential applications in heavy-ion physics
Towards the understanding of heavy quarks hadronization: from leptonic to heavy-ion collisions
No full textThe formation of hadrons is a fundamental process in nature that can be investigated at particle colliders. As several recent findings demonstrate, with collisions as a “vacuum-like” reference at one extreme, and central nucleus–nucleus as a dense, extended size system characterized by flow and local equilibrium at the opposite extreme, different collision systems offer a lever arm that can be exploited to probe with a range of heavy-flavour hadron species the onset of various hadronization processes. In this review, we present an overview of the theoretical and experimental developments. The focus is on open-heavy-flavour measurements. The comparison with model predictions and connections among the results in electron–positron, proton–proton, proton–nucleus, nucleus–nucleus collisions are discussed. After reviewing the current state, we suggest some prospects and future developments
Three-dimensional magnetohydrodynamics simulations of relativistic heavy-ion collisions with a black-hole accretion code adapted for quark-gluon plasma (BHAC-QGP). I. Methods and tests
No full textWe present bhac-qgp, a new numerical code to simulate the evolution of matter created in heavy-ion collisions in the presence of electromagnetic fields. It is derived from the Black Hole Accretion Code (BHAC), which has been designed to model astrophysical processes in a general-relativistic magnetohydrodynamical description. As the original Black Hole Accretion Code, BHAC QGP benefits from the use of adaptive mesh refinement, which allows us to dynamically adjust the resolution where necessary and makes use of time-dependent Milne coordinates and the ultrarelativistic equation of state, =/3. We demonstrate that bhac-qgp accurately passes a number of systematic and rigorous tests
Three-dimensional magnetohydrodynamics simulations of relativistic heavy-ion collisions with a black-hole accretion code adapted for quark-gluon plasma (BHAC-QGP). II. Application to Au-Au collisions
No full textWe present BHAC-QGP, a new numerical code to simulate the evolution of matter created in heavy-ion collisions. BHAC-QGP is based on the Black Hole Accretion Code (BHAC), which has been designed to model astrophysical processes through the solution of the equations of general-relativistic magnetohydrodynamics. Like the mother code, BHAC-QGP uses Adaptive Mesh Refinement (AMR), which allows for a dynamic adjustment of the resolution in regions of the computational domain where a particularly high accuracy is needed. We here discuss a number of applications of BHAC-QGP to Au-Au collisions at Relativistic Heavy-Ion Collider (RHIC) energies and show that the code is able to reproduce results of other simulations of these scenarios, but with much higher accuracy
