Elliptic flow of thermal dileptons as a probe of QCD matter

TL;DR

This paper investigates how the elliptic flow of thermal dileptons varies with momentum and mass in Pb+Pb collisions at high energy, aiming to use dileptons as probes of the quark-gluon plasma and hadronic matter properties.

Contribution

It provides a detailed analysis of dilepton elliptic flow considering medium effects and space-time evolution, offering a method to distinguish properties of different phases of QCD matter.

Findings

Elliptic flow decreases for invariant mass beyond phi meson mass.

Selection of mass and momentum windows can reveal medium effects.

Results suggest dileptons can probe the partonic phase elliptic flow.

Abstract

We study the variation of elliptic flow of thermal dileptons with transverse momentum and invariant mass of the pairs for Pb+Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV. The dilepton productions from quark gluon plasma (QGP) and hot hadrons have been considered including the spectral change of light vector mesons in the thermal bath. The space time evolution has been carried out within the frame work of 2+1 dimensional ideal hydrodynamics with lattice+hadron resonance gas equation of state. We find that a judicious selection of invariant mass(M) and transverse momentum (p_T) windows can be used to extract the collective properties of quark matter, hadronic matter and also get a distinct signature of medium effects on vector mesons. Our results indicate a reduction of elliptic flow (v_2) for M beyond phi mass, which if observed experimentally would give the measure of v_2 of the partonic phase.