Speaker
Description
Two-particle correlations are emerging as powerful tools for studying the medium produced in heavy-ion collisions. In particular, two-particle transverse momentum correlations enable measurements of the collision dynamics sensitive to momentum currents. Their evolution with collision multiplicity, as proxy of the system lifetime, gives information about the specific shear viscosity, $\eta/s$, and the system relaxation time, $\tau_{\pi}$.
Particle production measured at low momenta in small collision systems, such as pp and p--Pb, at LHC energies points to manifestations of collective behavior, longitudinal long-range correlations, and large azimuthal anisotropy, that suggests those small systems may produce short-lived QGP matter similar to that observed in Pb--Pb collisions.
In this talk, measurements of two-particle transverse momentum correlators in pp, p--Pb, and Pb--Pb collisions are presented. The strength and shape of the correlators are studied as functions of the produced particle multiplicity to identify evidence for longitudinal broadening that might reveal the presence of viscous effects expected to arise in fluid-like systems produced in those collisions. The measured correlators, their strengths and shapes, are additionally compared to model predictions and their evolution, along the pp, p--Pb, and Pb--Pb systems, is discussed.
