Decreasing elliptic flow at the LHC: Calculations in a parton recombination approach

TL;DR

This paper uses a parton recombination model to predict a decrease in elliptic flow at LHC energies, contrasting with previous expectations, due to negative v_2 values at certain momentum ranges.

Contribution

It introduces a novel application of the parton recombination approach to predict elliptic flow behavior at LHC energies, highlighting a decrease contrary to prior assumptions.

Findings

Good description of v_2 data from AGS to RHIC energies.

Prediction of decreased v_2 at LHC energies.

Potential for negative v_2 values at very high energies.

Abstract

We apply the parton recombination approach to study the energy dependence of the elliptic flow, v_2 in heavy ion collisions from AGS to LHC energies. The relevant input quantities ($T, \mu_B, \eta_T$) at the various center of mass energies are obtained from fits to the available data. The model yields a good description of the integrated v_2 data for charged particles at midrapidity from AGS to RHIC energies. In stark contrast to the current expectations, we observe a decrease of the integrated v_2 values above the highest RHIC energy. Thus, we predict a decrease of v_2 at LHC energies compared to the RHIC results. This drop is attributed to negative v_2 values for the underlying parton distributions at low to moderate transverse momenta that develops if the transverse flow velocity is high enough. At energies above the LHC regime, the present approach predicts even negative values for the integrated v_2.