Investigating jet induced identified hadron productions from the relative transverse activity classifier in pp collision at LHC

TL;DR

This work investigates jet-induced identified hadron production in pp collisions at $\sqrt{s}=13$ TeV using the AMPT model with PYTHIA8 initial conditions. By classifying events with the relative transverse activity $R_T$ and comparing toward, transverse, and in-jet regions (with in-jet yields defined by Toward minus Transverse), the study isolates jet-related effects from the underlying event. The results show that final-state partonic and hadronic interactions in AMPT can reproduce key features of the data and produce a distinctive crossing behavior in in-jet $p/\pi$ ratios at intermediate $p_T$, highlighting potential jet-medium interactions in small systems. The methodology offers a complementary perspective to full jet reconstruction, enabling sensitivity to soft jet fragments and guiding future explorations of jet quenching from small to large collision systems.

Abstract

In this work, we systematically investigate the jet associated identified hadron productions of pions, kaons, and protons based on the event topological separation method in proton proton (pp) collisions at $\sqrt{s}=13$ TeV employing the AMPT model with PYTHIA8 initial conditions. Enabling relative transverse event activity classifier $R_T$, we analyze the transverse momentum ($p_T$) spectra and particle ratios in the jet aligned toward region and the underlying event (UE) contributions sensitive transverse region varying with $R_T$. The results indicate that the AMPT model, incorporating both partonic and hadronic final-state interactions, provides a satisfactory description to the experimental data of the $p_T$ differential yields, particle ratios and average transverse momentum of identified particles in both the toward and transverse regions across different event activity classes. By subtracting the UE contribution from the toward region using the transverse region hadron yield, we introduce the in-jet hadron productions to analyze the modifications to jet itself. We find that the in-jet baryon to meson ratios reveal a sensitive dependence on $R_T$ driven by final state interactions, leading to a unique crossing pattern at intermediate $p_T$. This behavior can be regarded as a novel signature for probing jet medium interactions and energy loss effects in small collision systems.

Figures (7)

• Figure 1: $\pi$, K, p production in different event topological regions relative to the leading particle: $|\Delta\phi|<60^\circ$ (Toward), $|\Delta\phi|>120^{\circ}$ (Away), and $60^\circ<|\Delta\phi|<120^\circ$ (Transverse), with $\Delta\phi$ being the azimuthal angle of the emitted particle relative to that of the leading particle.
• Figure 2: Transverse momentum spectra of $\pi^{\pm}$, $K^{\pm}$, and $p(\bar{p})$ in toward (left column) and transverse (right column) regions. The AMPT model calculations for $R_T$ integrated events, $0<R_T<0.5$ and $2.5<R_T<5$ are shown in the black lines, red lines and blue lines, respectively. ALICE data for $R_T$ integrated events taken from Ref. ALICE:2023yuk are indicated by the open markers for comparison.
• Figure 3: Ratio of the transverse-momentum spectra in the toward region to those in the transverse region for different $R_T$ event classes. The black, red and blue lines represent the results for the all events, $0<R_T<0.5$ and $2.5<R_T<5$, respectively. The $0<R_T<0.5$ results have been scaled by a factor 0.1 to allow comparison on the same vertical scale.
• Figure 4: K/$\pi$ and p/$\pi$ ratios as a function of $p_T$ for two $R_T$ intervals in toward (upper panel) and transverse (lower panel) region. The AMPT results without final state rescatterings (0 mb w/o ART), with only final state parton rescatterings (0.15 mb w/o ART), with all final state interactions (0.15 mb w/ ART) are shown with black and red lines in left, middle and right column, respectively. ALICE data within corresponding $R_T$ ranges taken from Ref. ALICE:2023yuk are indicated by the open markers for comparison.
• Figure 5: Mid-rapidity particle yields as a function of $R_T$ for $\pi$ (top row), $K$ (middle row) and proton (bottom row). The results in the toward and transverse regions are shown black and red lines. The AMPT calculations without final state rescatterings (0 mb w/o ART), with only final state parton rescatterings (0.15 mb w/o ART), with all final state interactions (0.15 mb w/ ART) are shown in left, middle and right column, respectively.