Speaker
Description
In this work we present the production of charged particles associated with high-$p_{\rm T}$ trigger particles ($8<\textit{p}_{\rm T}^{\rm trig.}<15$ GeV/$c$) at midrapidity in proton-proton collisions at $\sqrt{s}=5.02$,TeV simulated with the PYTHIA 8 Monte Carlo model [1]. The study is performed as a function of the relative transverse activity classifier, $R_{\rm T}$, which is the relative charged-particle multiplicity in the transverse region ($\pi/3< \phi^{\rm trig.}-\phi^{\rm assoc.}|<2\pi/3$) of the di-hadron correlations, and it is sensitive to the Multi-Parton Interactions. The evolution of the yield of associated particles on both the towards and the away regions ($3\leq p_{\rm T}^{\rm assoc.}< 8$ GeV/$c$) as a function of $R_{\rm T}$ is investigated. We propose a strategy which allows for the modelling and subtraction of the Underlying Event (UE) contribution from the towards and the away regions in challenging environments like those characterised by large $R_{\rm T}$. We found that the signal in the away region becomes broader with increasing $R_{\rm T}$. Contrarily, the yield increases with $R_{\rm T}$ in the towards region. This effect is reminiscent of that seen in heavy-ion collisions, where an enhancement of the yield in the towards region for 0-5% central Pb$-$Pb collisions at $\sqrt{s_{\rm NN}}=2.76$,TeV was reported. To further understand the role of the UE and additional jet activity, the transverse region is divided into two one-sided sectors, "trans-max" and "trans-min" selected in each event according to which region has larger or smaller charged particle multiplicity. Based on this selection criterium, the observables are studied as a function of $R_{\rm T}^{\rm max}$ and $R_{\rm T}^{\rm min}$, respectively. Results for pp collisions simulated with PYTHIA 8.244 and Herwing 7.2 will be shown.
[1] J.Phys.G 48 (2020) 1, 015007
