Overview
- CMS reported the observation Friday, July 17, using lead‑lead collisions recorded in 2018 compared with proton‑proton references from 2017 to isolate the signal.
- The team selected back‑to‑back dijet events with a leading jet above 130 GeV and a subleading jet above 50 GeV and used a pseudorapidity‑gap subtraction to expose a depletion behind jets.
- The deficit is clearest for charged particles with transverse momentum between 1 and 2 GeV in the 0–30% most central collisions and exceeds five standard deviations in that central range.
- Hydrodynamic-based models and jet‑energy‑loss calculations reproduce the wake’s shape but generally predict a stronger depletion than measured, showing current models understate how the plasma redistributes deposited momentum.
- The result is a statistical inference built from many collisions rather than a picture of a single quark, and the next steps are independent cross‑checks, more differential measurements, and model refinement to pin down the plasma’s transport properties.