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| Main Authors: | , |
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| Format: | Preprint |
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2026
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| Online Access: | https://arxiv.org/abs/2602.19566 |
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| _version_ | 1866913169267490816 |
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| author | Roy, Subhadeep Dash, Sadhana |
| author_facet | Roy, Subhadeep Dash, Sadhana |
| contents | Understanding the origin of collectivity-like signatures in small collision systems is a central open question in high-energy nuclear physics, and two-particle correlation functions offer unique sensitivity to the underlying-event (UE) dynamics that may drive such behavior in proton--proton (pp) collisions. In this work, the two-particle number ($R_{2}$) and transverse-momentum ($P_{2}$) correlation functions are studied in pp collisions at $\sqrt{s}=13$ TeV using PYTHIA 8, for final state charged hadrons within $|η|<0.8$ and $0.2<p_{\rm T}<2.0$ GeV/$c$, with events classified by the relative transverse activity $R_{\mathrm{T}}$ to probe how UE activity shapes correlation structures in the soft-QCD-dominated regime. A collectivity-like long-range near-side component is observed in the charge-independent correlator $R_{2}^{\mathrm{CI}}$ exclusively for the highest $R_{\mathrm{T}}$ class ($2.5 < R_{\mathrm{T}} \leq 5.0$), while no corresponding structure appears in the charge-dependent correlators. This indicates that enhanced UE activity, driven by multiple partonic interactions and color reconnection, can generate collectivity-like long-range correlations without hydrodynamic evolution. These findings establish $R_{\mathrm{T}}$ as a differential event classifier to provide a non-hydrodynamic baseline for interpreting such signatures in small-system measurements at the LHC. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2602_19566 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Relative transverse activity as a probe of collectivity-like long-range correlations in pp collisions at $\sqrt{s}=13$ TeV Roy, Subhadeep Dash, Sadhana High Energy Physics - Phenomenology Understanding the origin of collectivity-like signatures in small collision systems is a central open question in high-energy nuclear physics, and two-particle correlation functions offer unique sensitivity to the underlying-event (UE) dynamics that may drive such behavior in proton--proton (pp) collisions. In this work, the two-particle number ($R_{2}$) and transverse-momentum ($P_{2}$) correlation functions are studied in pp collisions at $\sqrt{s}=13$ TeV using PYTHIA 8, for final state charged hadrons within $|η|<0.8$ and $0.2<p_{\rm T}<2.0$ GeV/$c$, with events classified by the relative transverse activity $R_{\mathrm{T}}$ to probe how UE activity shapes correlation structures in the soft-QCD-dominated regime. A collectivity-like long-range near-side component is observed in the charge-independent correlator $R_{2}^{\mathrm{CI}}$ exclusively for the highest $R_{\mathrm{T}}$ class ($2.5 < R_{\mathrm{T}} \leq 5.0$), while no corresponding structure appears in the charge-dependent correlators. This indicates that enhanced UE activity, driven by multiple partonic interactions and color reconnection, can generate collectivity-like long-range correlations without hydrodynamic evolution. These findings establish $R_{\mathrm{T}}$ as a differential event classifier to provide a non-hydrodynamic baseline for interpreting such signatures in small-system measurements at the LHC. |
| title | Relative transverse activity as a probe of collectivity-like long-range correlations in pp collisions at $\sqrt{s}=13$ TeV |
| topic | High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2602.19566 |