Particle production as a function of the Underlying Event activity in small and large systems and search for jet-like modifications in ALICE

14 Nov 2022, 10:20
WG1: Monte Carlo, MB, and UE WG1: Monte Carlo, MB, and UE


Omar Vazquez Rueda (University of Houston)


Multiple measurements of high-multiplicity pp and p-A collisions at LHC energies have revealed that these small collision systems exhibit some of the quark-gluon plasma features, e.g. collective behaviour and strangeness enhancement, formerly thought to be achievable only in heavy-ion collisions. The dependence on multiplicity suggests significant final-state interactions. A proposed method to narrow down the origin of the phenomena is to study the effect of Multi-Parton Interactions (MPIs). Although the MPIs cannot be measured directly, the event observable $R_{\mathrm{T}}$, quantifying the magnitude of the underlying event, has been suggested as an experimental proxy.

Measurements of the charged particle production as a function of $R_{\mathrm{T}}$ in pp, p-Pb and Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02~\mathrm{TeV}$ with the ALICE experiment will be presented in the toward, away and transverse regions. The UE contributions measured in the transverse region are subtracted from the toward and the away regions to search for jet-like modifications in small systems. The jet-like signals are studied both as a function of $R_{\mathrm{T}}$ and leading particle $p_{\mathrm{T}}$.

Finally, the results on the production of $\pi$, K, p, $\phi$ and $\Xi$ as a function of $R_{\mathrm{T}}$ in pp collisions at $\sqrt{s}=13~\mathrm{TeV}$ are presented to explore the particle species dependence. In particular, the focus will be on the very low (high) $R_{\mathrm{T}}$ to isolate the “jet” (UE) contributions. All the above results are compared with predictions from QCD-inspired Monte Carlo event generators such as PYTHIA and EPOS-LHC.

Primary author

Omar Vazquez Rueda (University of Houston)

Presentation Materials

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