Discovering partonic rescattering in light nucleus collisions – Aleksas Mazeliauskas (CERN)

October 26, 2021 @ 4:00 pm – 5:00 pm
Heribertus Bayu Hartanto

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]

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