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Title: Importance of non-flow in mixed-harmonic multi-particle correlations in small collision systems

Abstract

Recently CMS Collaboration measured mixed-harmonic four-particle azimuthal correlations, known as symmetric cumulants SC(n, m), in pp and p+Pb collisions, and interpreted the non-zero SC(n, m) as evidence for long-range collectivity in these small collision systems. Using the PYTHIA and HIJING models which do not have genuine long-range collectivity, we show that the CMS results, obtained with standard cumulant method, could be dominated by non-flow effects associated with jet and dijets, especially in pp collisions. We show that the non-flow effects are largely suppressed using the recently proposed subevent cumulant methods by requiring azimuthal correlation between two or more pseudorapidity ranges. As a result, we argue that the reanalysis of SC(n, m) using the subevent method in experiments is necessary before they can used to provide further evidences for a long-range multi-particle collectivity and constraints on theoretical models in small collision systems.

Authors:
 [1];  [2]; ORCiD logo [3]; ORCiD logo [2]
  1. Stony Brook Univ., Stony Brook, NY (United States)
  2. Univ. of Copenhagen, Copenhagen (Denmark)
  3. Stony Brook Univ., Stony Brook, NY (United States); Brookhaven National Lab. (BNL), Upton, NY (United States)
Publication Date:
Research Org.:
Brookhaven National Lab. (BNL), Upton, NY (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
OSTI Identifier:
1439313
Report Number(s):
BNL-205708-2018-JAAM
Journal ID: ISSN 0370-2693; TRN: US1900601
Grant/Contract Number:  
SC0012704
Resource Type:
Accepted Manuscript
Journal Name:
Physics Letters. Section B
Additional Journal Information:
Journal Volume: 777; Journal Issue: C; Journal ID: ISSN 0370-2693
Publisher:
Elsevier
Country of Publication:
United States
Language:
English
Subject:
73 NUCLEAR PHYSICS AND RADIATION PHYSICS

Citation Formats

Huo, Peng, Gajdosova, Katarina, Jia, Jiangyong, and Zhou, You. Importance of non-flow in mixed-harmonic multi-particle correlations in small collision systems. United States: N. p., 2017. Web. doi:10.1016/j.physletb.2017.12.035.
Huo, Peng, Gajdosova, Katarina, Jia, Jiangyong, & Zhou, You. Importance of non-flow in mixed-harmonic multi-particle correlations in small collision systems. United States. doi:10.1016/j.physletb.2017.12.035.
Huo, Peng, Gajdosova, Katarina, Jia, Jiangyong, and Zhou, You. Mon . "Importance of non-flow in mixed-harmonic multi-particle correlations in small collision systems". United States. doi:10.1016/j.physletb.2017.12.035. https://www.osti.gov/servlets/purl/1439313.
@article{osti_1439313,
title = {Importance of non-flow in mixed-harmonic multi-particle correlations in small collision systems},
author = {Huo, Peng and Gajdosova, Katarina and Jia, Jiangyong and Zhou, You},
abstractNote = {Recently CMS Collaboration measured mixed-harmonic four-particle azimuthal correlations, known as symmetric cumulants SC(n, m), in pp and p+Pb collisions, and interpreted the non-zero SC(n, m) as evidence for long-range collectivity in these small collision systems. Using the PYTHIA and HIJING models which do not have genuine long-range collectivity, we show that the CMS results, obtained with standard cumulant method, could be dominated by non-flow effects associated with jet and dijets, especially in pp collisions. We show that the non-flow effects are largely suppressed using the recently proposed subevent cumulant methods by requiring azimuthal correlation between two or more pseudorapidity ranges. As a result, we argue that the reanalysis of SC(n, m) using the subevent method in experiments is necessary before they can used to provide further evidences for a long-range multi-particle collectivity and constraints on theoretical models in small collision systems.},
doi = {10.1016/j.physletb.2017.12.035},
journal = {Physics Letters. Section B},
number = C,
volume = 777,
place = {United States},
year = {2017},
month = {12}
}

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Figures / Tables:

Figure 1 Figure 1: The SC(n,m) calculated for charged particles with 0.3 < pT < 3 GeV with the standard cumulant method in 13 TeV pp collisions (left panel) and 5.02 TeV p+Pb collisions (right panel) compared between data (solid symbols) and Monte Carlo models (open symbols).

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Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.