Jan 10 – 15, 2021
Weizmann Institute of Science
Asia/Jerusalem timezone
See you at IS2023 in Copenhagen in June 2023

Study of Underlying Event activity in pp and p-Pb collisions at $\sqrt{s_{ NN}}=5.02$ TeV with ALICE.

Jan 10, 2021, 7:45 PM
1h 30m
Patio (vDLCC)



bullet talk (poster) Multiparton interactions Poster


Ahsan Mehmood Khan (Central China Normal University CCNU (CN))


One of the most important discoveries at the LHC is the observation of collective-like behavior and strangeness enhancement in small collision systems (e.g. pp and p-Pb collisions). They effects are strikingly similar to those observed in heavy-ion collisions, where they are attributed to the production of a deconfined hot and dense medium, known as strongly interacting Quark-Gluon Plasma. In order to gain insight into the physics mechanisms behind these effects in small systems, in this work we measure Underlying Event (UE) activity in pp and p-Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV. UE collects contributions from Multi-Partonic Interactions (MPI) as well as particles from initial- and final-state radiation related to the hardest component. The average number density and the average total transverse momentum ($p_{\rm T}$) as a function of the $p_{\rm T}$ of the leading particle will be presented. Results for three topological regions will be shown: near and away side (sensitive to the jet-like component) and the transverse side (sensitive to UE). Three different cut-off values for track $p_{\rm T}$ are considered. i.e. 0.15, 0.5 and 1 GeV/$c$. The jet-like component is also analyzed after the subtraction of the UE component. Comparisons between the UE activity for pp collisions at different center of mass energies, and among pp and p-Pb collisions will be shown. Moreover, we will compare the measurements to QCD-inspired Monte Carlo event generators for the three different topological regions.

Primary author

Ahsan Mehmood Khan (Central China Normal University CCNU (CN))

Presentation materials