Measurement of the groomed jet mass in PbPb and pp collisions at $\sqrt{s_{_\mathrm{NN}}} =$ 5.02 TeV

Understand

A measurement of the groomed jet mass in PbPb and pp collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV with the CMS detector at the LHC is presented.

• Jet grooming is a recursive procedure which sequentially removes soft constituents of a jet until a pair of hard subjets is found.
• The resulting groomed jets can be used to study modifications to the parton shower evolution in the presence of the hot and dense medium created in heavy ion collisions.
• Predictions of groomed jet properties from the PYTHIA and HERWIG++ event generators agree with the measurements in pp collisions.