Observation of medium-induced yield enhancement and acoplanarity broadening of low-pT jets in pp and Pb-Pb collisions at √sNN = 5.02 TeV with ALICE

We present the measurements of the semi-inclusive distributions of charged-particle jets recoiling from a trigger hadron in proton–proton (pp) and 0–10% Pb–Pb collisions at √sNN=5.02 TeV, searching for medium-induced yield enhancement and acoplanarity broadening effects in low transverse momentum (pT) jets. This technique provides precise data-driven subtraction of the large uncorrelated background yield in jet measurements, enabling the measurement of recoil jet distributions to the large jet radius at low pT in central Pb--Pb collisions. Trigger-normalized recoil jet distributions are reported as a function of pT,jet and as a function of the azimuthal angle (Δφ) between trigger hadron axis and recoil jet. Comparisons of the jet yield distributions in pp and Pb–Pb collisions show a significant medium-induced yield enhancement at low pT and at large-angle jet deflection for large radius. Comparisons to theoretical calculations incorporating jet quenching will also be discussed.