| 1. |
- Adare, A., et al.
(författare)
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Energy loss and flow of heavy quarks in Au+Au collisions at root s(NN) = 200 GeV
- 2007
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Ingår i: Physical Review Letters. - 1079-7114. ; 98:17
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Tidskriftsartikel (refereegranskat)abstract
- The PHENIX experiment at the BNL Relativistic Heavy Ion Collider (RHIC) has measured electrons with 0.3 < p(T) < 9 GeV/c at midrapidity (y < 0.35) from heavy-flavor (charm and bottom) decays in Au + Au collisions at root s(NN) = 200 GeV. The nuclear modification factor R-AA relative to p + p collisions shows a strong suppression in central Au + Au collisions, indicating substantial energy loss of heavy quarks in the medium produced at RHIC energies. A large azimuthal anisotropy v(2) with respect to the reaction plane is observed for 0.5 < p(T) < 5 GeV/c indicating substantial heavy-flavor elliptic flow. Both R-AA and v(2) show a p(T) dependence different from those of neutral pions. A comparison to transport models which simultaneously describe R-AA(p(T)) and v(2)(p(T)) suggests that the viscosity to entropy density ratio is close to the conjectured quantum lower bound, i.e., near a perfect fluid.
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| 2. |
- Adare, A., et al.
(författare)
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Scaling properties of azimuthal anisotropy in Au plus Au and Cu plus Cu collisions at root s(NN)=200 GeV
- 2007
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Ingår i: Physical Review Letters. - 1079-7114. ; 98:16
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Tidskriftsartikel (refereegranskat)abstract
- Differential measurements of elliptic flow (v(2)) for Au+Au and Cu+Cu collisions at root s(NN)=200 GeV are used to test and validate predictions from perfect fluid hydrodynamics for scaling of v(2) with eccentricity, system size, and transverse kinetic energy (KET). For KET equivalent to m(T)-m up to similar to 1 GeV the scaling is compatible with hydrodynamic expansion of a thermalized fluid. For large values of KET mesons and baryons scale separately. Quark number scaling reveals a universal scaling of v(2) for both mesons and baryons over the full KET range for Au+Au. For Au+Au and Cu+Cu the scaling is more pronounced in terms of KET, rather than transverse momentum.
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| 3. |
- Adare, A., et al.
(författare)
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System size and energy dependence of jet-induced hadron pair correlation shapes in Cu+Cu and Au+Au collisions at root S-NN 200 and 62.4 GeV
- 2007
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Ingår i: Physical Review Letters. - 1079-7114. ; 98:23
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Tidskriftsartikel (refereegranskat)abstract
- We present azimuthal angle correlations of intermediate transverse momentum (1-4 GeV/c) hadrons from dijets in Cu+Cu and Au+Au collisions at root s(NN)=62.4 and 200 GeV. The away-side dijet induced azimuthal correlation is broadened, non-Gaussian, and peaked away from Delta phi=pi in central and semicentral collisions in all the systems. The broadening and peak location are found to depend upon the number of participants in the collision, but not on the collision energy or beam nuclei. These results are consistent with sound or shock wave models, but pose challenges to Cherenkov gluon radiation models.
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| 4. |
- Adcox, K, et al.
(författare)
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Formation of dense partonic matter in relativistic nucleus-nucleus collisions at RHIC: Experimental evaluation by the PHENIX Collaboration
- 2005
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Ingår i: Nuclear Physics, Section A. - : Elsevier BV. - 0375-9474. ; 757:1-2, s. 184-283
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Forskningsöversikt (refereegranskat)abstract
- Extensive experimental data from high-energy nucleus-nucleus collisions were recorded using the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The comprehensive set of measurements from the first three years of RHIC operation includes charged particle multiplicities, transverse energy, yield ratios and spectra of identified hadrons in a wide range of transverse momenta (PT), elliptic flow, two-particle correlations, nonstatistical fluctuations, and suppression of particle production at high PT. The results are examined with an emphasis on implications for the formation of a new state of dense matter. We find that the state of matter created at RHIC cannot be described in terms of ordinary color neutral hadrons.
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| 5. |
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| 6. |
- Adler, SS, et al.
(författare)
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Common suppression pattern of eta and pi(0) mesons at high transverse momentum in Au plus Au collisions at root SNN=200 GeV
- 2006
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Ingår i: Physical Review Letters. - 1079-7114. ; 96:20
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Tidskriftsartikel (refereegranskat)abstract
- Inclusive transverse momentum spectra of eta mesons have been measured within p(T)=2-10 GeV/c at midrapidity by the PHENIX experiment in Au+Au collisions at root s(NN) = 200 GeV. In central Au+Au the eta yields are significantly suppressed compared to peripheral Au+Au, d+Au, and p+p yields scaled by the corresponding number of nucleon-nucleon collisions. The magnitude, centrality, and p(T) dependence of the suppression is common, within errors, for eta and pi(0). The ratio of eta to pi(0) spectra at high p(T) amounts to 0.40 < R-eta/pi(0)< 0.48 for the three systems, in agreement with the world average measured in hadronic and nuclear reactions and, at large scaled momentum, in e(+)e(-) collisions.
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| 7. |
- Adler, SS, et al.
(författare)
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Deuteron and antideuteron production in Au+Au collisions at root s(NN)=200 GeV
- 2005
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Ingår i: Physical Review Letters. - 1079-7114. ; 94:12
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Tidskriftsartikel (refereegranskat)abstract
- The production of deuterons and antideuterons in the transverse momentum range 1.1 < p(T)< 4.3 GeV/c at midrapidity in Au+Au collisions at root s(NN) = 200 GeV has been studied by the PHENIX experiment at RHIC. A coalescence analysis, comparing the deuteron and antideuteron spectra with that of proton and antiproton, has been performed. The coalescence probability is equal for both deuterons and antideuterons and it increases as a function of p(T), which is consistent with an expanding collision zone. Comparing (anti)proton yields, (p) over bar /p = 0.73 +/- 0.01, with (anti)deuteron yields, (d) over bar /d = 0.47 +/- 0.03, we estimate that (n) over bar /n = 0.64 +/- 0.04. The nucleon phase space density is estimated from the coalescence measurement.
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| 8. |
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| 9. |
- Adler, SS, et al.
(författare)
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Measurement of single electron event anisotropy in Au plus Au collisions at root s(NN)=200 GeV
- 2005
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 72:2
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Tidskriftsartikel (refereegranskat)abstract
- The transverse momentum dependence of the azimuthal anisotropy parameter v(2), the second harmonic of the azimuthal distribution, for electrons at midrapidity (vertical bar eta vertical bar < 0.35) has been measured with the PHENIX detector in Au+Au collisions at root s(NN) = 200 GeV. The measurement was made with respect to the reaction plane defined at high rapidities (vertical bar eta vertical bar = 3.1-3.9). From the result we have measured the v(2) of electrons from heavy flavor decay after subtraction of the v(2) of electrons from other sources such as photon conversions and Dalitz decay from light neutral mesons. We observe a nonzero single electron v(2) with a 90% confidence level in the intermediate-p(T) region. The precision of the present data set does not permit us to conclude definitively that heavy quarks exhibit thermalization with the transverse flow of the bulk matter.
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| 10. |
- Adler, SS, et al.
(författare)
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Measurement of transverse single-spin asymmetries for midrapidity production of neutral pions and charged hadrons in polarized p+p collisions at root s=200 GeV
- 2005
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Ingår i: Physical Review Letters. - 1079-7114. ; 95
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Tidskriftsartikel (refereegranskat)abstract
- Transverse single-spin asymmetries to probe the transverse-spin structure of the proton have been measured for neutral pions and nonidentified charged hadrons from polarized proton-proton collisions at midrapidity and root s = 200 GeV. The data cover a transverse momentum (pT) range 1.0-5.0 GeV/c for neutral pions and 0.5-5.0 GeV/c for charged hadrons, at a Feynman-x value of approximately zero. The asymmetries seen in this previously unexplored kinematic region are consistent with zero within errors of a few percent. In addition, the inclusive charged hadron cross section at midrapidity from 0.5 < P-T < 7.0 GeV/c is presented and compared to next-to-leading order perturbative QCD ( pQCD) calculations. Successful description of the unpolarized cross section above similar to 2 GeV/c suggests that pQCD is applicable in the interpretation of the asymmetry results in the relevant kinematic range.
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