Observation of medium-induced yield enhancement and acoplanarity broadening of low-p ₓ jets in pp and Pb-Pb collisions at s ₍₍ = 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 (p ₓ) 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 p ₓ in central Pb--Pb collisions. Trigger-normalized recoil jet distributions are reported as a function of p ₓ, ₉₄ₓ and as a function of the azimuthal angle () 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 p ₓ and at large-angle jet deflection for large radius. Comparisons to theoretical calculations incorporating jet quenching will also be discussed.