| 11. |
- Adare, A., et al.
(författare)
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Forward J/ψ production in U + U collisions at sNN =193 GeV
- 2016
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Ingår i: Physical Review C. - 2469-9985. ; 93:3
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Tidskriftsartikel (refereegranskat)abstract
- The invariant yields, dN/dy, for J/ψ production at forward rapidity (1.2<|y|<2.2) in U+U collisions at sNN=193GeV have been measured as a function of collision centrality. The invariant yields and nuclear-modification factor RAA are presented and compared with those from Au+Au collisions in the same rapidity range. Additionally, the direct ratio of the invariant yields from U+U and Au+Au collisions within the same centrality class is presented, and used to investigate the role of cc coalescence. Two different parametrizations of the deformed Woods-Saxon distribution were used in Glauber calculations to determine the values of the number of nucleon-nucleon collisions in each centrality class, Ncoll, and these were found to give significantly different Ncoll values. Results using Ncoll values from both deformed Woods-Saxon distributions are presented. The measured ratios show that the J/ψ suppression, relative to binary collision scaling, is similar in U+U and Au+Au for peripheral and midcentral collisions, but that J/ψ show less suppression for the most central U+U collisions. The results are consistent with a picture in which, for central collisions, increase in the J/ψ yield due to cc coalescence becomes more important than the decrease in yield due to increased energy density. For midcentral collisions, the conclusions about the balance between cc coalescence and suppression depend on which deformed Woods-Saxon distribution is used to determine Ncoll.
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| 12. |
- Adare, A., et al.
(författare)
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Systematic study of azimuthal anisotropy in Cu plus Cu and Au plus Au collisions at root s(NN)=62.4 and 200 GeV
- 2015
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 92:3
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the dependence of azimuthal anisotropy nu(2) for inclusive and identified charged hadrons in Au + Au and Cu + Cu collisions on collision energy, species, and centrality. The values of nu(2) as a function of transverse momentum pT and centrality in Au + Au collisions at root s(NN) = 200 and 62.4 GeV are the same within uncertainties. However, in Cu + Cu collisions we observe a decrease in nu(2) values as the collision energy is reduced from 200 to 62.4 GeV. The decrease is larger in the more peripheral collisions. By examining both Au + Au and Cu + Cu collisions we find that nu(2) depends both on eccentricity and the number of participants, N-part. We observe that nu(2) divided by eccentricity (epsilon) monotonically increases with N-part and scales as N-part(1/3). The Cu + Cu data at 62.4 GeV falls below the other scaled nu(2) data. For identified hadrons, nu(2) divided by the number of constituent quarks n(q) is independent of hadron species as a function of transverse kinetic energy K E-T = m(T) - m between 0.1 < K E-T / n(q) < 1 GeV. Combining all of the above scaling and normalizations, we observe a near-universal scaling, with the exception of the Cu + Cu data at 62.4 GeV, of nu(2)/(nq center dot e center dot N-part(1/3)) vs K E-T / n(q) for all measured particles.
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| 13. |
- Adare, A., et al.
(författare)
-
PHENIX Collaboration
- 2016
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Ingår i: ; , s. 964-970
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Konferensbidrag (refereegranskat)
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| 14. |
- Adare, A., et al.
(författare)
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phi meson production in d plus Au collisions at root s(NN)=200 GeV
- 2015
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 92:4
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Tidskriftsartikel (refereegranskat)abstract
- The PHENIX Collaboration has measured phi meson production in d + Au collisions at root s(NN) = 200 GeV using the dimuon and dielectron decay channels. The phi meson is measured in the forward (backward) d-going (Au-going) direction, 1.2 < y < 2.2 (-2.2 < y < -1.2) in the transverse-momentum (pT) range from 1-7 GeV/c and at midrapidity vertical bar y vertical bar < 0.35 in the p(T) range below 7 GeV/c. The phi meson invariant yields and nuclear-modification factors as a function of p(T), rapidity, and centrality are reported. An enhancement of phi meson production is observed in the Au-going direction, while suppression is seen in the d-going direction, and no modification is observed at midrapidity relative to the yield in p + p collisions scaled by the number of binary collisions. Similar behavior was previously observed for inclusive charged hadrons and open heavy flavor, indicating similar cold-nuclear-matter effects.
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| 15. |
- Adare, A., et al.
(författare)
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Centrality categorization Rp(d)+A in high-energy collisions
- 2014
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 90:3
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Tidskriftsartikel (refereegranskat)abstract
- High-energy proton- and deuteron-nucleus collisions provide an excellent tool for studying a wide array of physics effects, including modifications of parton distribution functions in nuclei, gluon saturation, and color neutralization and hadronization in a nuclear environment, among others. All of these effects are expected to have a significant dependence on the size of the nuclear target and the impact parameter of the collision, also known as the collision centrality. In this article, we detail a method for determining centrality classes in p(d) + A collisions via cuts on the multiplicity at backward rapidity (i.e., the nucleus-going direction) and for determining systematic uncertainties in this procedure. For d + Au collisions at root s(NN) = 200 GeV we find that the connection to geometry is confirmed by measuring the fraction of events in which a neutron from the deuteron does not interact with the nucleus. As an application, we consider the nuclear modification factors Rp(d)+A, for which there is a bias in the measured centrality-dependent yields owing to auto correlations between the process of interest and the backward-rapidity multiplicity. We determine the bias-correction factors within this framework. This method is further tested using the HIJING Monte Carlo generator. We find that for d + Au collisions at root s(NN) = 200 GeV, these bias corrections are small and vary by less than 5% (10%) up to p(T) = 10 (20) GeV/c. In contrast, for p + Pb collisions at v root s(NN) = 5.02 TeV we find that these bias factors are an order of magnitude larger and strongly pT dependent, likely attributable to the larger effect of multiparton interactions.
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| 16. |
- Adare, A., et al.
(författare)
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Ground and excited state charmonium production in p plus p collisions at root s=200 GeV
- 2012
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Ingår i: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 85:9
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Tidskriftsartikel (refereegranskat)abstract
- We report on charmonium measurements [J/psi (1S), psi' (2S), and chi(c) (1P)] in p + p collisions at root s = 200 GeV. We find that the fraction of J/psi coming from the feed-down decay of psi' and chi(c) in the midrapidity region (vertical bar y vertical bar < 0: 35) is 9.6 +/- 2.4% and 32 +/- 9%, respectively. We also present the p(T) and rapidity dependencies of the J/psi yield measured via dielectron decay at midrapidity (vertical bar y vertical bar < 0.35) and via dimuon decay at forward rapidity (1.2 < vertical bar y vertical bar < 2.2). The statistical precision greatly exceeds that reported in our previous publication [Phys. Rev. Lett. 98, 232002 (2007)]. The new results are compared with other experiments and discussed in the context of current charmonium production models.
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| 17. |
- Adare, A., et al.
(författare)
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Measurement of High-p(T) single electrons from heavy-flavor decays in p+p collisions at root s=200 GeV
- 2006
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Ingår i: Physical Review Letters. - 1079-7114. ; 97:25
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Tidskriftsartikel (refereegranskat)abstract
- The momentum distribution of electrons from decays of heavy flavor (charm and bottom) for midrapidity |y|< 0.35 in p+p collisions at s=200 GeV has been measured by the PHENIX experiment at the BNL Relativistic Heavy Ion Collider over the transverse momentum range 0.3 < p(T)< 9 GeV/c. Two independent methods have been used to determine the heavy-flavor yields, and the results are in good agreement with each other. A fixed-order-plus-next-to-leading-log perturbative QCD calculation agrees with the data within the theoretical and experimental uncertainties, with the data/theory ratio of 1.71 +/- 0.02(stat)+/- 0.18(sys) for 0.3 < p(T)< 9 GeV/c. The total charm production cross section at this energy has also been deduced to be sigma(cc)=567 +/- 57(stat)+/- 193(sys) mu b.
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| 18. |
- Adare, A., et al.
(författare)
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Measurement of transverse single-spin asymmetries for J/psi production in polarized p plus p collisions at root s=200 GeV
- 2010
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Ingår i: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 82:11
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Tidskriftsartikel (refereegranskat)abstract
- We report the first measurement of transverse single-spin asymmetries in J/psi production from transversely polarized p + p collisions at root s = 200 GeV with data taken by the PHENIX experiment in 2006 and 2008. The measurement was performed over the rapidity ranges 1.2 < vertical bar y vertical bar < 2.2 and vertical bar y vertical bar < 0.35 for transverse momenta up to 6 GeV/c. J/psi production at the Relativistic Heavy Ion Collider is dominated by processes involving initial-state gluons, and transverse single-spin asymmetries of the J/psi can provide access to gluon dynamics within the nucleon. Such asymmetries may also shed light on the long-standing question in QCD of the J/psi production mechanism. Asymmetries were obtained as a function of J/psi transverse momentum and Feynman-x, with a value of -0.086 +/- 0.026(stat) +/- 0.003(syst) in the forward region. This result suggests possible nonzero trigluon correlation functions in transversely polarized protons and, if well defined in this reaction, a nonzero gluon Sivers distribution function.
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| 19. |
- Adare, A., et al.
(författare)
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Cold nuclear matter effects on J/psi production as constrained by deuteron-gold measurements at root S-NN=200 GeV
- 2008
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 77:2, s. 15-024912
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Tidskriftsartikel (refereegranskat)abstract
- We present a new analysis of J/psi production yields in deuteron-gold collisions at root s(NN) =200 GeV using data taken from the PHENIX experiment in 2003 and previously published in S. S. Adler [Phys. Rev. Lett 96, 012304 (2006)]. The high statistics proton-proton J/psi data taken in 2005 are used to improve the baseline measurement and thus construct updated cold nuclear matter modification factors (R-dAu). A suppression of J/psi in cold nuclear matter is observed as one goes forward in rapidity (in the deuteron-going direction), corresponding to a region more sensitive to initial-state low-x gluons in the gold nucleus. The measured nuclear modification factors are compared to theoretical calculations of nuclear shadowing to which a J/psi (or precursor) breakup cross section is added. Breakup cross sections of sigma(breakup)=2.8(-1.4)(+1.7) (2.2(-1.5)(+1.6)) mb are obtained by fitting these calculations to the data using two different models of nuclear shadowing. These breakup cross-section values are consistent within large uncertainties with the 4.2 +/- 0.5 mb determined at lower collision energies. Projecting this range of cold nuclear matter effects to copper-copper and gold-gold collisions reveals that the current constraints are not sufficient to firmly quantify the additional hot nuclear matter effect.
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| 20. |
- Adare, A., et al.
(författare)
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Gluon-Spin Contribution to the Proton Spin from the Double-Helicity Asymmetry in Inclusive pi(0) Production in Polarized p plus p Collisions at root s=200 GeV
- 2009
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Ingår i: Physical Review Letters. - 1079-7114. ; 103:1
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Tidskriftsartikel (refereegranskat)abstract
- The double helicity asymmetry in neutral pion production for p(T) = 1 to 12 GeV/c was measured with the PHENIX experiment to access the gluon-spin contribution, Delta G, to the proton spin. Measured asymmetries are consistent with zero, and at a theory scale of mu 2 = 4 GeV2 a next to leading order QCD analysis gives Delta G([0.02,0.3]) = 0.2, with a constraint of -0.7 < Delta G([0.02,0.3]) < 0.5 at Delta chi(2) = 9 (similar to 3 sigma) for the sampled gluon momentum fraction (x) range, 0.02 to 0.3. The results are obtained using predictions for the measured asymmetries generated from four representative fits to polarized deep inelastic scattering data. We also consider the dependence of the Delta G constraint on the choice of the theoretical scale, a dominant uncertainty in these predictions.
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