Apparent modification of the jet-like yield in proton-proton collisions with large underlying event

Abstract

This paper presents the production of charged particles associated with high-$p_{\mathrm{T}}$ trigger particles ($8<p_{\mathrm{T}}^{trig.}<15$ GeV/$c$) in proton-proton collisions at $\sqrt{s}=5.02$ TeV simulated with PYTHIA 8.244. The study is performed as a function of the relative transverse activity classifier, $R_{\mathrm{T}}$, which is the relative charged-particle multiplicity in the transverse region ($\pi /3<|{\varphi }^{trig.}-{\varphi }^{assoc.}|<2\pi /3$) of the di-hadron correlations, and it is sensitive to the Multi-Parton Interactions. The evolution of both the near and the away-side yield of associated particles ($3\le p_{\mathrm{T}}^{assoc.}<8$ GeV/$c$) as a function of $R_{\mathrm{T}}$ is investigated. We propose a strategy which allows for the modelling and subtraction of the underlying event contribution from the near and the away side in challenging environments like those characterised by large $R_{\mathrm{T}}$. We found that the away-side signal becomes broader with increasing $R_{\mathrm{T}}$, while its corresponding yield is independent of $R_{\mathrm{T}}$. Contrarily, the near-side yield increases with $R_{\mathrm{T}}$. This effect is reminiscent of that seen in heavy-ion collisions, where an enhancement in the near-side yield for 0-5% central Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV was reported. A discussion on the origin of these effects in PYTHIA, as well as their implications for the interpretation of recent LHC results for pp collisions, is presented.

6 pages, 4 figures

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• Disentangling the hard gluon Bremsstrahlung effects from the relative transverse activity classifier in pp collisions
• Study of charged particle production at high $p_{\mathrm{T}}$ using event topology in pp, p$-$Pb and Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV
• Extraction of the multiplicity dependence of Multiparton Interactions from LHC pp data using Machine Learning techniques
• Energy dependence of underlying-event observables from RHIC to LHC energies
• Topological studies of light-flavor hadron production in pp, p-Pb, and Pb-Pb collisions with ALICE at the LHC
• Charged-particle production as a function of the relative transverse activity classifier in pp, p$-$Pb, and Pb$-$Pb collisions at the LHC
• Investigating the most active pp collisions (top 0.1%) using the tools developed by experiments at the LHC
• Investigating jet induced identified hadron productions from the relative transverse activity classifier in pp collision at LHC
• Defining the Underlying-Event Activity in the Presence of Heavy-Flavour Processes in Proton-Proton Collisions at LHC Energies