Search results for "kvarkki-gluoniplasma"

Measurement of an Excess in the Yield of J/ψ at Very Low pT in Pb-Pb Collisions at √sNN = 2.76 TeV

2016

We report on the first measurement of an excess in the yield of J=ψ at very low transverse momentum (pT < 0.3 GeV=c) in peripheral hadronic Pb-Pb collisions at √sNN=2.76  TeV, performed by ALICE at the CERN LHC. Remarkably, the measured nuclear modification factor of J=ψ in the rapidity range 2.5 <y< 4 reaches about 7 (2) in the pT range 0–0.3 GeV=c in the 70%–90% (50%–70%) centrality class. The J=ψ production cross section associated with the observed excess is obtained under the hypothesis that coherent photoproduction of J=ψ is the underlying physics mechanism. If confirmed, the observation of J=ψ coherent photoproduction in Pb-Pb collisions at impact parameters smaller than twice the nu…

Approach to equilibrium of a quarkonium in a quark-gluon plasma

2018

We derive equations of motion for the reduced density matrix of a heavy quarkonium in contact with a quark-gluon plasma in thermal equilibrium. These equations allow in particular a proper treatment of the regime when the temperature of the plasma is comparable to the binding energy of the quarkonium. These equations are used to study how the quarkonium approaches equilibrium with the plasma, and we discuss the corresponding entropy increase, or free energy decrease, depending on the temperature regime. The effect of collisions can be accounted for by the generalization of the imaginary potential introduced in previous studies, and from which collision rates are derived. An important outcom…

Creation of quark-gluon plasma droplets with three distinct geometries

2019

Experimental studies of the collisions of heavy nuclei at relativistic energies have established the properties of the quark–gluon plasma (QGP), a state of hot, dense nuclear matter in which quarks and gluons are not bound into hadrons1,2,3,4. In this state, matter behaves as a nearly inviscid fluid5 that efficiently translates initial spatial anisotropies into correlated momentum anisotropies among the particles produced, creating a common velocity field pattern known as collective flow. In recent years, comparable momentum anisotropies have been measured in small-system proton–proton (p+p) and proton–nucleus (p+A) collisions, despite expectations that the volume and lifetime of the medium…

Minijet initial state of heavy-ion collisions from next-to-leading order perturbative QCD

2014

Measurements of the groomed jet radius and momentum splitting fraction with the soft drop and dynamical grooming algorithms in pp collisions at √s = …

2023

This article presents measurements of the groomed jet radius and momentum splitting fraction in pp collisions at √ s = 5.02 TeV with the ALICE detector at the Large Hadron Collider. Inclusive charged-particle jets are reconstructed at midrapidity using the anti-kT algorithm for transverse momentum 60< 80 GeV/c. We report results using two different grooming algorithms: soft drop and, for the first time, dynamical grooming. For each grooming algorithm, a variety of grooming settings are used in order to explore the impact of collinear radiation on these jet substructure observables. These results are compared to perturbative calculations that include resummation of large logarithms at all or…

Measurement of inclusive and leading subjet fragmentation in pp and Pb–Pb collisions at √sNN = 5.02 TeV

2023

This article presents new measurements of the fragmentation properties of jets in both proton–proton (pp) and heavy-ion collisions with the ALICE experiment at the Large Hadron Collider (LHC). We report distributions of the fraction zr of transverse momentum carried by subjets of radius r within jets of radius R. Charged-particle jets are reconstructed at midrapidity using the anti-kT algorithm with jet radius R = 0.4, and subjets are reconstructed by reclustering the jet constituents using the anti-kT algorithm with radii r = 0.1 and r = 0.2. In proton–proton collisions, we measure both the inclusive and leading subjet distributions. We compare these measurements to perturbative calculatio…

Dielectron production at midrapidity at low transverse momentum in peripheral and semi-peripheral Pb–Pb collisions at √sNN = 5.02 TeV

2023

Underlying-event properties in pp and p–Pb collisions at √sNN = 5.02 TeV

2023

We report about the properties of the underlying event measured with ALICE at the LHC in pp and p–Pb collisions at √sNN = 5.02 TeV. The event activity, quantified by charged-particle number and summed-pT densities, is measured as a function of the leading-particle transverse momentum (ptrigT). These quantities are studied in three azimuthal-angle regions relative to the leading particle in the event: toward, away, and transverse. Results are presented for three different pT thresholds (0.15, 0.5 and 1 GeV/c) at mid-pseudorapidity (|η| 10 GeV/c, whereas for lower ptrigT values the event activity is slightly higher in p–Pb than in pp collisions. The measurements are compared with predictions …

A Monte Carlo simulation for the elastic energy loss of high-energy partons in a strongly interacting medium

2012

Quasiparticle properties of nonequilibrium gluon plasma

2018

We apply classical gluodynamics to early stages of ultrarelativistic heavy-ion collisions. We start by giving a brief overview of QCD. Then we proceed to the space-time evolution of ultrarelativistic heavy-ion collisions in the color glass condensate framework and go through the basics of real-time gluodynamics on the lattice in the temporal gauge. We study the plasmon mass scale in three- and two-dimensional systems by comparing three different methods to measure the mass scale. The methods are a formula which can be derived from Hard Thermal Loop effective theory at leading order (HTL), the effective dispersion relation (DR) and measurement of the plasma oscillation frequency triggered by th…