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A<sc>bstract</sc> Correlations in azimuthal angle extending over a long range in pseudorapidity between particles, usually called the “ridge” phenomenon, were discovered in heavy-ion collisions, and later found in pp and p–Pb collisions. In large systems, they are thought to arise from the expansion (collective flow) of the produced particles. Extending these measurements over a wider range in pseudorapidity and final-state particle multiplicity is important to understand better the origin of these long-range correlations in small collision systems. In this Letter, measurements of the long-range correlations in p–Pb collisions at$$ \sqrt{s_{\textrm{NN}}} $$ = 5.02 TeV are extended to a pseudorapidity gap of ∆η~ 8 between particles using the ALICE forward multiplicity detectors. After suppressing non-flow correlations, e.g., from jet and resonance decays, the ridge structure is observed to persist up to a very large gap of ∆η~ 8 for the first time in p–Pb collisions. This shows that the collective flow-like correlations extend over an extensive pseudorapidity range also in small collision systems such as p–Pb collisions. The pseudorapidity dependence of the second-order anisotropic flow coefficient,v2(η), is extracted from the long-range correlations. Thev2(η) results are presented for a wide pseudorapidity range of –3.1< η <4.8 in various centrality classes in p–Pb collisions. To gain a comprehensive understanding of the source of anisotropic flow in small collision systems, thev2(η) measurements are compared with hydrodynamic and transport model calculations. The comparison suggests that the final-state interactions play a dominant role in developing the anisotropic flow in small collision systems.
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Multiplicity and event-scale dependent flow and jet fragmentation in pp collisions at $$ \sqrt{s} $$ = 13 TeV and in p–Pb collisions at $$ \sqrt{s_{\textrm{NN}}} $$ = 5.02 TeV
A<sc>bstract</sc> Long- and short-range correlations for pairs of charged particles are studied via two-particle angular correlations in pp collisions at$$ \sqrt{s} $$ = 13 TeV and p–Pb collisions at$$ \sqrt{s_{\textrm{NN}}} $$ = 5.02 TeV. The correlation functions are measured as a function of relative azimuthal angle ∆φand pseudorapidity separation ∆ηfor pairs of primary charged particles within the pseudorapidity interval |η|<0.9 and the transverse-momentum interval 1< pT<4 GeV/c. Flow coefficients are extracted for the long-range correlations (1.6<|∆η|<1.8) in various high-multiplicity event classes using the low-multiplicity template fit method. The method is used to subtract the enhanced yield of away-side jet fragments in high-multiplicity events. These results show decreasing flow signals toward lower multiplicity events. Furthermore, the flow coefficients for events with hard probes, such as jets or leading particles, do not exhibit any significant changes compared to those obtained from high-multiplicity events without any specific event selection criteria. The results are compared with hydrodynamic-model calculations, and it is found that a better understanding of the initial conditions is necessary to describe the results, particularly for low-multiplicity events.
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- PAR ID:
- 10514245
- Author(s) / Creator(s):
- ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; more »
- Publisher / Repository:
- link.springer.com
- Date Published:
- Journal Name:
- Journal of High Energy Physics
- Volume:
- 2024
- Issue:
- 3
- ISSN:
- 1029-8479
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1007/JHEP03(2024)092
