Anomalous centrality evolution of two-particle angular correlations from Au-Au collisions at √sNN = 62 and 200 GeV

Znanstveni rad - Izvorni znanstveni rad

• Autor: G. Agakishiev
• Autor: ...
• Autor: Mirko Planinić
• Autor: ...
• Autor: Nikola Poljak
• Autor: ...
• Autor: Y. Zoulkarneeva
• Kolaboracija: STAR Collaboration
• Autorova ustanova: Sveučilište u Zagrebu; Prirodoslovno-matematički fakultet; (Fizički odsjek)
• Znanstveno / umjetničko područje, polje i grana: PRIRODNE ZNANOSTI; Fizika

Sažetak (engleski)

We present two-dimensional (2D) two-particle angular correlations measured with the STAR detector on relative pseudorapidity η and azimuth ϕ for charged particles from Au-Au collisions at √sNN=62 and 200 GeV with transverse momentum pt≥0.15 GeV/c, |η|≤1, and 2π in azimuth. Observed correlations include a same-side (relative azimuth <π/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 η width of the same-side 2D peak also increases rapidly (η elongation), and the ϕ 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.

• Ključne riječi (engleski): anomalous; centrality; correlations; STAR
• Jezik: engleski
• Vrsta publikacije: Znanstveni rad - Izvorni znanstveni rad
• Status objave: Objavljen
• Vrsta recenzije: Recenziran - međunarodna recenzija
• Verzija publikacije: Objavljena verzija rada (izdavačev PDF)
• Naslov časopisa: Physical Review C - Nuclear Physics
• Brojčani podaci: vol. 86, br. 6, 064902
• p-ISSN: 0556-2813
• e-ISSN: 1089-490X
• DOI: https://doi.org/10.1103/PhysRevC.86.064902
• URN:NBN: urn:nbn:hr:217:207894
• Datum objave publikacije: 2012
• Projekt: Šifra: 119-0982887-1006; Naziv (hrvatski): Istraživanje hadronskih sustava upotrebom relativističkih projektila; Voditelj: Mirko Planinić; Pravna nadležnost: Hrvatska; Financijer: MZOS; Linija financiranja: ZP
• URL dokumenta: http://link.aps.org/doi/10.1103/PhysRevC.86.064902
• Vrsta resursa: Tekst
• Prava pristupa: Otvoreni pristup
• Javna napomena: Copyright (2012) by the American Physical Society. Received 17 September 2011; revised manuscript received 11 November 2012; published 12 December 2012.
• Datum i vrijeme pohrane: 2019-11-21 12:25:00