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Title: Revealing long-range multiparticle collectivity in small collision systems via subevent cumulants

Journal Article · · Physical Review C
 [1];  [2];  [3]
  1. Stony Brook Univ., NY (United States). Department of Chemistry; Brookhaven National Lab. (BNL), Upton, NY (United States). Physics Department
  2. Stony Brook Univ., NY (United States). Department of Chemistry
  3. Polish Academy of Sciences, Krakow (Poland). Institute of Nuclear Physics

Multi-particle azimuthal cumulants, often used to study collective flow in high-energy heavy-ion collisions, have recently been applied in small collision systems such as pp and p+A to extract the second-order azimuthal harmonic flow v2. Recent observation of four-, six- and eight-particle cumulants with “correct sign” c2{4} < 0, c2{6} > 0, c2{8} < 0 and approximate equality of the inferred single-particle harmonic flow, v2{4} ≈ v2{6} ≈ v2{8}, have been used as strong evidence for a collective emission of all soft particles produced in the collisions. In this paper, we show that these relations in principle could be violated due to the non-Gaussianity in the event-by-event fluctuation of flow and/or non-flow. Furthermore, we show, using pp events generated with the PYTHIA model, that c2{2k} obtained with standard cumulant method are dominated by non-flow from dijets. An alternative cumulant method based on two or more η-separated subevents is proposed to suppress the dijet contribution. The new method is shown to be able to recover a flow signal as low as 4% imposed on the PYTHIA events, independently of how the event activity class is defined. Therefore the subevent cumulant method offers a more robust way of studying collectivity based on the existence of long-range azimuthal correlations between multiple distinct η ranges. Finally, the prospect of using the subevent cumulants to study collective flow in A+A collisions, in particular its longitudinal dynamics, is discussed.

Research Organization:
Brookhaven National Lab. (BNL), Upton, NY (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Nuclear Physics (NP)
Grant/Contract Number:
SC0012704
OSTI ID:
1430890
Report Number(s):
BNL-203404-2018-JAAM; PRVCAN; TRN: US1802926
Journal Information:
Physical Review C, Vol. 96, Issue 3; ISSN 2469-9985
Publisher:
American Physical Society (APS)Copyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 60 works
Citation information provided by
Web of Science

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Influence of initial-state momentum anisotropy on the final-state collectivity in small collision systems journal December 2019
Measurement of longitudinal flow decorrelations in Pb+Pb collisions at $$\sqrt{s_{\text {NN}}}=2.76$$ s NN = 2.76 and 5.02 TeV with the ATLAS detector journal February 2018
Multiparticle Production and Initial Quasitemperature from Proton-Induced Carbon Collisions at p Lab = 31  GeV/ c journal January 2020
Investigations of Anisotropic Flow Using Multiparticle Azimuthal Correlations in $pp$, $p-Pb$, Xe-Xe, and Pb-Pb Collisions at the LHC text January 2019
Observation of correlated azimuthal anisotropy Fourier harmonics in pp and pPb collisions at the LHC text January 2017
Observation of Correlated Azimuthal Anisotropy Fourier Harmonics in p p and p + Pb Collisions at the LHC journal February 2018
Effect of the QCD equation of state and strange hadronic resonances on multiparticle correlations in heavy ion collisions text January 2017
Centrality fluctuations in heavy-ion collisions text January 2018
Influence of initial-state momentum anisotropy on the final-state collectivity in small collision systems text January 2019