Measurement of substructure-dependent suppression of large-radius jets with charged particles in Pb+Pb collisions with ATLAS

Measurements of jet substructure in Pb+Pb collisions provide key insights into the mechanism of jet quenching in the hot and dense QCD medium created in these collisions. This Letter presents a measurement of the suppression of large-radius jets with a radius parameter of R = 1.0 and its dependence on the jet substructure. The measurement uses 1.72 nb^-1 of Pb+Pb data and 255 pb^-1 of pp data, both at √s_NN = 5.02 TeV, recorded with the ATLAS detector at the Large Hadron Collider. Large-radius jets are reconstructed by reclustering R = 0.2 calorimetric jets and are measured for transverse momentum above 200 GeV. Jet substructure is evaluated using charged-particle tracks, and the overall level of jet suppression is quantified using the jet nuclear modification factor (R_AA). The jet R_AA is measured as a function of jet p_T, the charged k_t splitting scale (√d₁₂), and the angular separation (dR₁₂) of two leading sub-jets. The jet R_AA gradually decreases with increasing √d₁₂, implying significantly stronger suppression of large-radius jets with larger k_t splitting scale. The jet R_AA gradually decreases for dR₁₂ in the range 0.01-0.2 and then remains consistent with a constant for dR₁₂ \gtrsim 0.2. The observed significant dependence of jet suppression on the jet substructure will provide new insights into its role in the quenching process.