Ratios of jet and hadron spectra at LHC energies: measuring high-$p_T$ suppression without a $pp$ reference

Abstract

In this work we analyze the reliability of several techniques for computing jet and hadron spectra at different collision energies. This is of particular relevance for discovering energy loss in the upcoming oxygen-oxygen (OO) run at the LHC, for which a reference pp run at the same energy is currently not planned. For hadrons and jets we compute the ratio of spectra between different pp collision energies in perturbative QCD, which can be used to construct a pp reference spectrum. Alternatively, a pp reference can be interpolated from measured spectra at nearby energies. We estimate the precision and accuracy of both strategies for the spectra ratio relevant to the oxygen run, and conclude that the central values agree to 4% accuracy for hadrons and 2% accuracy for jets. As an alternative, we propose taking the ratio of OO and $pp$ spectra at different collision energies, which cleanly separates the experimental measurement from the theoretical computation.