Abstract

Ultrarelativistic collisions of heavy ions produce high density de-confined QCD matter known as Quark-Gluon Plasma, which expands as a small droplet of nearly perfect fluid. There is mounting experimental evidence that various signals of collectivity (indicative of soft partonic rescattering and QGP formation) are present in all hadron collisions, including proton-proton and proton-lead systems. The absence of measurable high momentum jet and hadron modification in proton-lead and peripheral lead-lead collisions is however one of outstanding problems in the field of heavy ion physics. As the medium induced modifications of these hard probes is expected to be small, one needs precision tools to make the discovery. In our recent Letter we demonstrate that planned oxygen-oxygen (OO) collisions during LHC Run 3 provide unprecedented sensitivity to parton energy loss in a system only several times larger than proton-proton collisions. With leading and next-to-leading order perturbative QCD calculations of nuclear modification factors, we show that the baseline in the absence of partonic rescattering is known with up to 2% theoretical accuracy in inclusive OO collisions. We study a broad range of parton energy loss models and we find that the expected signal of partonic rescattering can be disentangled from the baseline by measuring charged hadron spectra in the range 20 GeV< pT < 100 GeV.

Ref.: Huss, Kurkela, Mazeliauskas, Paatelainen, van der Schee, Wiedemann, Phys.Rev.Lett. 126 (2021) 19, 192301 [2007.13754]