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Anomalous centrality evolution of two-particle angular correlations from Au-Au collisions at root s(NN)=62 and 200 GeV
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SYSNO ASEP 0388197 Document Type J - Journal Article R&D Document Type Journal Article Subsidiary J Článek ve WOS Title Anomalous centrality evolution of two-particle angular correlations from Au-Au collisions at root s(NN)=62 and 200 GeV Author(s) Agakishiev, G. (RU)
Aggarwal, M. M. (IN)
Ahammed, Z. (IN)
Alakhverdyants, A. V. (RU)
Alekseev, I. (RU)
Alford, J. (US)
Anderson, B. D. (US)
Anson, C. (US)
Arkhipkin, D. (US)
Averichev, G. S. (RU)
Balewski, J. (US)
Bielčíková, Jana (UJF-V) RID, ORCID, SAI
Chaloupka, Petr (UJF-V) RID
Chung, Paul (UJF-V)
Hajková, O. (CZ)
Kapitán, Jan (UJF-V)
Pachr, M. (CZ)
Rusňák, Jan (UJF-V) RID, ORCID, SAI
Šumbera, Michal (UJF-V) RID, ORCID, SAI
Tlustý, David (UJF-V)Number of authors 353 Source Title Physical Review. C - ISSN 0556-2813
Roč. 86, č. 6 (2012), s. 064902Number of pages 30 s. Language eng - English Country US - United States Keywords heavy ion collisions ; QCD matter ; STAR Subject RIV BG - Nuclear, Atomic and Molecular Physics, Colliders R&D Projects LA09013 GA MŠMT - Ministry of Education, Youth and Sports (MEYS) Institutional support UJF-V - RVO:61389005 UT WOS 000312293400004 DOI 10.1103/PhysRevC.86.064902 Annotation We present two-dimensional (2D) two-particle angular correlations measured with the STAR detector on relative pseudorapidity eta and azimuth phi for charged particles from Au-Au collisions at root s(NN) = 62 and 200 GeV with transverse momentum p(t) >= 0.15 GeV/c, vertical bar eta vertical bar <= 1, and 2 pi in azimuth. Observed correlations include a same-side (relative azimuth <pi/2) 2D peak, a closely related away-side azimuth dipole, and an azimuth quadrupole conventionally associated with elliptic flow. The same-side 2D peak and away-side dipole are explained by semihard parton scattering and fragmentation (minijets) in proton-proton and peripheral nucleus-nucleus collisions. Those structures follow N-N binary-collision scaling in Au-Au collisions until midcentrality, where a transition to a qualitatively different centrality trend occurs within one 10% centrality bin. Above the transition point the number of same-side and away-side correlated pairs increases rapidly relative to binary-collision scaling, the eta width of the same-side 2D peak also increases rapidly (eta elongation), and the phi width actually decreases significantly. Those centrality trends are in marked contrast with conventional expectations for jet quenching in a dense medium. The observed centrality trends are compared to perturbative QCD predictions computed in HIJING, which serve as a theoretical baseline, and to the expected trends for semihard parton scattering and fragmentation in a thermalized opaque medium predicted by theoretical calculations and phenomenological models. We are unable to reconcile a semihard parton scattering and fragmentation origin for the observed correlation structure and centrality trends with heavy-ion collision scenarios that invoke rapid parton thermalization. If the collision system turns out to be effectively opaque to few-GeV partons the present observations would be inconsistent with the minijet picture discussed here. Workplace Nuclear Physics Institute Contact Markéta Sommerová, sommerova@ujf.cas.cz, Tel.: 266 173 228 Year of Publishing 2013
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