Anomalous centrality evolution of two-particle angular correlations from Au-Au collisions at root s(NN)=62 and 200 GeV
Contribuinte(s) |
UNIVERSIDADE DE SÃO PAULO |
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Data(s) |
01/11/2013
01/11/2013
2012
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Resumo |
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. DOI: 10.1103/PhysRevC.86.064902 RHIC Operations Group and RCF at BNL RHIC Operations Group and RCF at BNL NERSC Center at LBNL NERSC Center at LBNL Open Science Grid consortium Open Science Grid consortium Offices of NP and HEP within the U.S. DOE Office of Science offices of NP and HEP within the US DOE Office of Science US NSF U.S. NSF Sloan Foundation Sloan Foundation DFG cluster of excellence Origin and Structure of the Universe of Germany DFG cluster of excellence "Origin and Structure of the Universe" of Germany CNRS/IN2P3 CNRS/IN2P3 FAPESP CNPq of Brazil FAPESP CNPq of Brazil Ministry of Education and Science of the Russian Federation Ministry of Education and Science of the Russian Federation NNSFC NNSFC CAS CAS MoST MoST MoE of China MoE of China GA GA MSMT of the Czech Republic MSMT of the Czech Republic FOM FOM NWO of the Netherlands NWO of the Netherlands DAE DAE DST DST CSIR of India CSIR of India Polish Ministry of Science and Higher Education Polish Ministry of Science and Higher Education Korea Research Foundation Korea Research Foundation Ministry of Science, Education and Sports of the Republic of Croatia Ministry of Science, Education, and Sports of the Republic of Croatia RosAtom of Russia RosAtom of Russia |
Identificador |
PHYSICAL REVIEW C, COLLEGE PK, v. 86, n. 6, supl. 1, Part 6, pp. 491-501, DEC 12, 2012 0556-2813 http://www.producao.usp.br/handle/BDPI/37458 10.1103/PhysRevC.86.064902 |
Idioma(s) |
eng |
Publicador |
AMER PHYSICAL SOC COLLEGE PK |
Relação |
PHYSICAL REVIEW C |
Direitos |
openAccess Copyright AMER PHYSICAL SOC |
Palavras-Chave | #QUARK-GLUON PLASMA #HEAVY-ION COLLISIONS #NUCLEUS-NUCLEUS COLLISIONS #TRANSVERSE-MOMENTUM #CROSS-SECTIONS #PERFECT LIQUID #QCD MATTER #ENERGY #MODEL #THERMALIZATION #PHYSICS, NUCLEAR |
Tipo |
article original article publishedVersion |