Speaker
Description
Small collision systems, such as pp or p-Pb, exhibit signatures of collective effects that are thought to be associated with quark-gluon plasma formation. The absence to date of jet quenching signals raises a question about the origin of the observed collectivity and calls for more accurate jet quenching measurements in small collision systems. In this poster, the ALICE Collaboration reports results of a novel approach to search for jet quenching effects in high-multiplicity pp collisions at $\sqrt{s}$ = 13 TeV, which are selected based on charged-particle multiplicity measured using forward scintillator detectors. In the analysis, we look for broadening of the azimuthal acoplanarity measured by the semi-inclusive distribution of charged-jets recoiling from a high transverse momentum, charged trigger hadron. Jet reconstruction is performed using anti-$k_{\rm {T}}$ algorithm with $R$ = 0.4. The measured jet yield is corrected for uncorrelated background,including multi-partonic interaction, by means of a data-driven statistical method. Comparison of recoil jet distributions measured in minimum bias and high-multiplicity events reveals significant broadening in the high-multiplicity data, resembling jet quenching. However, a qualitatively similar feature is observed in pp data simulated with the PYTHIA 8 generator, which does not account for jet quenching. We will discuss the current status of the analysis, and prospects to understand the origin of this striking phenomenon.
