Can one extract energy loss probability distributions from R_AA?

TL;DR

This paper investigates whether the energy loss probability distribution in heavy-ion collisions can be extracted solely from R_AA measurements, concluding that additional observables are necessary for a model-independent determination.

Contribution

It provides a conceptual analysis showing the limitations of using R_AA alone to invert and determine the energy loss distribution in high-energy nuclear collisions.

Findings

R_AA measurements alone are insufficient for a model-independent extraction of energy loss distributions.

Additional observables like gamma-hadron correlations are needed for a complete inversion.

The study emphasizes the complexity of interpreting suppression factors in heavy-ion collision experiments.

Abstract

The nuclear suppression of high transverse momentum P_T hadrons is one of the most striking findings in heavy-ion collision experiments. It has long been recognized that the suppression can be theoretically described by folding the primary parton spectrum with an energy loss probability distribution which is suitably averaged over the collision geometry. However, an interesting problem is to what degree the procedure can be inverted, i.e. given a measurement of the suppression factor R_AA with arbitrary precision, can the probability distribution of energy loss be extracted in a model-independent way? In this note, we present a conceptual study of the inversion problem for LHC energies and demonstrate that a measurement of R_AA alone is insufficient to determine the distribution, other observables such as gamma-hadron correlations must be taken into account.