2025/10/03 by Arjun Srinivasan Kudinoor, Kudinoor, Arjun Srinivasan, Daniel Pablos +3
Physics and Astronomy · #Particle physics theoretical and experimental studies #Quantum Chromodynamics and Particle Interactions #High-Energy Particle Collisions Research
paper · pdf · doi:10.48550/arxiv.2510.03390
We report on our investigation in arXiv:2509.08881 of how recent jet substructure measurements constrain the resolution length L\rm res of the quark-gluon plasma formed in heavy-ion collisions. L\rm res is defined such that high-energy partons within a jet shower are resolved by the medium if and only if they are separated by a distance greater than L\rm res. Using the Hybrid Model, we reproduce ALICE data on the scaled Soft Drop angle θg for R=0.2 charged-particle jets and ATLAS data on the Hard Group angle ΔR12 for R=1 jets reclustered from skinny R = 0.2 inclusive subjets. We find that the narrowing of the θg-distribution in PbPb collisions observed by ALICE and the suppression of R=1 jets with multiple skinny subjets in PbPb collisions observed by ATLAS rule out L\rm res = ∞, where each entire parton shower loses energy to the plasma coherently as if it were a single colored object. We then compare Hybrid Model calculations to ATLAS measurements of R\rm AA of R=1 jets reclustered from R=0.2 subjets, as a function of the Soft Drop angle dR12 obtained by grooming all charged-particle tracks associated with each R=1 jet. We demonstrate, for the first time, that the ATLAS data is inconsistent with L\rm res = 0, where the plasma resolves every splitting in a parton shower. Our results agree best with the data when QGP possesses a finite, nonzero L\rm res∼ (1-2)/(πT).