Physicists map how extreme heat destroys particle jets differently
Researchers at CERN have discovered that particle jets behave unpredictably when exposed to extreme temperatures, with damage varying based on their internal structure. The finding could refine models used in nuclear physics research and improve predictions about matter behavior under extreme conditions—insights with potential applications in energy research and materials science.
Originaltitel: Measurement of substructure-dependent suppression of large-radius jets with charged particles in Pb+Pb collisions with ATLAS
<p>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<sup>−1</sup> of Pb+Pb data and 255 pb<sup>−1</sup> of <em>pp</em> data, both at √<sup>s</sup><sub>NN</sub>=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 (<em>R</em><sub>AA</sub>). The jet <em>R</em><sub>AA</sub> is measured as a function of jet <em>p</em><sub>T</sub>, the charged <em>k<sub>t</sub></em> splitting scale (√d12), and the angular separation (Δ<em>R</em><sub>12</sub>) of two leading sub-jets. The jet <em>R</em><sub>AA</sub> gradually decreases with increasing √d12, implying significantly stronger suppression of large-radius jets with larger <em>k<sub>t</sub></em> splitting scale. The jet <em>R</em><sub>AA</sub> gradually decreases for Δ<em>R</em><sub>12</sub> in the range 0.01−0.2 and then remains consistent with a constant for Δ<em>R</em><sub>12</sub> ≳ 0.2. The observed significant dependence of jet suppression on the jet substructure will provide new insights into its role in the quenching process.</p>