Effects of Minijets on Common Observables in Heavy-Ion Collisions with Uncommon Implications

TL;DR

This paper reviews how minijets influence observables in heavy-ion collisions, showing they can reproduce key spectra and anisotropies without hydrodynamics, highlighting a parameter-free approach that captures system footprints.

Contribution

It demonstrates that minijet contributions alone can explain low-$p_T$ spectra and azimuthal anisotropy without hydrodynamic modeling, offering a parameter-free alternative.

Findings

Minijets reproduce $v_2(p_T,b)$ and low-$p_T$ spectra.

Azimuthal anisotropy is calculated directly in momentum space.

No additional parameters are needed compared to hydrodynamic models.

Abstract

In this brief review of the observable effects of minijets in heavy-ion collisions the main points emphasized are that the quadruple moment $v_2(p_T,b)$ and the hadronic ($\pi$ and $p$) spectra at low $p_T$ can both be reproduced by minijet contributions to the recombination of thermal and shower partons. Without using hydrodynamics the minijet approach does not trace the evolution of the expanding system. The thermal distribution of the medium partons at the time of hadronization is assumed, but rapid thermalization initially is not required so as to allow minijets to leave their footprints on the system in the final state. Azimuthal anisotropy due to minijets is directly calculated in the momentum space without any fluid assumption relating the spatial eccentricity to $v_2$. There are no more parameters used, compared to the hydro approach in fitting the data on $v_2$ and $p_T$ spectra. Thus both approaches satisfy the sufficiency condition for a viable description of the dynamical process involved.