Improving the vacuum baseline for in-medium jet physics studies

The theoretical efforts from the past decades, together with the steadily growing available energy in Heavy-Ion (HI) colliders, led to the discovery of the Quark-Gluon Plasma (QGP), a short-lived QCD medium behaving as a hot low viscosity fluid.

Being so short-lived, the study of this medium relies on a comparison between proton-proton (pp) and HI collisions, making the baseline precision, i.e. precision of pp events, crucial for a precise QGP estimation.

Jets --- clusters of collimated particles sprays produced concurrently with the collision --- will be modified as they traverse this medium and can be used to access its dynamics.

This work delved into the jet substructure modifications arising from an improved pp baseline in HI collisions, by computing the hard-scattering at NLO.

To this end, a pp dijet analysis was done in the ALICE kinematical regime, with further quenching modifications simulated using antenna-configuration based models, in order to probe coherence effects at the substructure level.

Two analysis were conducted, one at fixed-order using MADGRAPH, with the quenching models applied to the hard-scattering NLO configuration and another one considering the full parton shower, with the event generation simulated with PYTHIA and the matched hard-scattering generated with POWHEG.

The results show an overall agreement with ALICE data, when considering the full parton shower.

Moreover, they also suggests some of the jet substructure modifications can be explained without considering any explicit broadening effect.

This agreement was found when using both baselines and for two parton shower algorithms, PYTHIA default shower and VINCIA shower.

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