Speaker
Description
The quark-gluon plasma, which is formed in heavy-ion collisions, can be studied by investigating how parton fragmentation is modified while passing through it. Two-particle angular correlations are useful to study the interactions of partons and the flowing medium in a transverse momentum regime where, after hadronization, jets cannot be reconstructed event-by-event above the fluctuating background.
In this contribution, results from two-particle angular correlation measurements by the ALICE collaboration from Pb-Pb and pp collisions will be presented. In these measurements, the distribution of the azimuthal angle (Δφ) and pseudorapidity (Δη) difference of particle pairs is studied. In such a distribution, jets manifest themselves as a near-side peak around (Δφ, Δη) = (0, 0) and as an elongated structure on the away side around Δφ = π. The shape of the near-side jet peak is characterized as a function of the collisions centrality and the transverse momentum of the particles. It will be shown that the near-side jet peak becomes broader and asymmetric towards low transverse momentum and that a novel feature, a depletion around (Δφ, Δη) = (0, 0) develops at low transverse momentum. The results are compared to A Multi-Phase Transport model (AMPT), which suggests that the observed effects are accompanied by large radial and longitudinal flow.
