Search for Jet Quenching in High-multiplicity $pp$ Collisions Using Inclusive and Semi-inclusive Jet Production in ALICE

These proceedings report on recent experimental searches for jet-quenching effects in pp collisions at √ s = 13 TeV. The measurements are based on two jet observables: inclusive jet production and the semi-inclusive yield of jets recoiling from a high-transverse-momentum (pT) hadron. Both measurements are carried out differentially in event multiplicity, which is assumed to bias the size of the collision system. To search for jet quenching effects, the shape of the inclusive jet yield in different multiplicity intervals is compared to the one obtained in minimum bias (MB) events. The increase in selected charged-particle multiplicity causes a rise in the jet yield but only minor changes in the slope of the jet spectrum above 20 GeV/c. In the semi-inclusive analysis, recoil jet acoplanarity is measured for events selected on high multiplicity (HM) and compared to the MB population. A striking modification of the acoplanarity distribution, which is nominally characteristic of jet quenching, is observed in the measured HM population. Its origin is elucidated by comparisons with PYTHIA calculations.