| 1. |
- Adare, A., et al.
(author)
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Azimuthally anisotropic emission of low-momentum direct photons in Au + Au collisions at sNN =200 GeV
- 2016
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In: Physical Review C: covering nuclear physics. - 2469-9985. ; 94:6
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Journal article (peer-reviewed)abstract
- The PHENIX experiment at the BNL Relativistic Heavy Ion Collider has measured second- and third-order Fourier coefficients of the azimuthal distributions of direct photons emitted at midrapidity in Au+Au collisions at sNN=200 GeV for various collision centralities. Combining two different analysis techniques, results were obtained in the transverse momentum range of 0.4
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| 2. |
- Adare, A., et al.
(author)
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Beam Energy and Centrality Dependence of Direct-Photon Emission from Ultrarelativistic Heavy-Ion Collisions
- 2019
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In: Physical Review Letters. - 1079-7114. ; 123:2
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Journal article (peer-reviewed)abstract
- The PHENIX collaboration presents first measurements of low-momentum (0.41 GeV/c) direct-photon yield dNγdir/dη is a smooth function of dNch/dη and can be well described as proportional to (dNch/dη)α with α≈1.25. This scaling behavior holds for a wide range of beam energies at the Relativistic Heavy Ion Collider and the Large Hadron Collider, for centrality selected samples, as well as for different A+A collision systems. At a given beam energy, the scaling also holds for high pT (>5 GeV/c), but when results from different collision energies are compared, an additional sNN-dependent multiplicative factor is needed to describe the integrated-direct-photon yield. © 2019 authors. Published by the American Physical Society.
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| 3. |
- Adare, A., et al.
(author)
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Centrality dependence of low-momentum direct-photon production in Au plus Au collisions at root s(NN)=200 GeV
- 2015
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In: Physical Review C (Nuclear Physics). - 0556-2813. ; 91:6
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Journal article (peer-reviewed)abstract
- The PHENIX experiment at RHIC has measured the centrality dependence of the direct photon yield from Au + Au collisions at root s(NN) = 200 GeV down to pT = 0.4 GeV/c. Photons are detected via photon conversions to e(+)e(-) pairs and an improved technique is applied that minimizes the systematic uncertainties that usually limit direct photon measurements, in particular at low pT. We find an excess of direct photons above the N-coll-scaled yield measured in p + p collisions. This excess yield is well described by an exponential distribution with an inverse slope of about 240 MeV/c in the pT range 0.6-2.0 GeV/c. While the shape of the pT distribution is independent of centrality within the experimental uncertainties, the yield increases rapidly with increasing centrality, scaling approximately with N-part(alpha), where alpha = 1.38 +/- 0.03(stat) +/- 0.07(syst).
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| 4. |
- Adare, A., et al.
(author)
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Charged-pion cross sections and double-helicity asymmetries in polarized p plus p collisions at root s=200 GeV
- 2015
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In: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 91:3
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Journal article (peer-reviewed)abstract
- We present midrapidity charged-pion invariant cross sections, the ratio of the pi(-) to pi(+) cross sections and the charge-separated double-spin asymmetries in polarized p + p collisions at root s = p + 200 GeV. While the cross section measurements are consistent within the errors of next-to-leading-order (NLO) perturbative quantum chromodynamics predictions (pQCD), the same calculations overestimate the ratio of the charged-pion cross sections. This discrepancy arises from the cancellation of the substantial systematic errors associated with the NLO-pQCD predictions in the ratio and highlights the constraints these data will place on flavor-dependent pion fragmentation functions. The charge-separated pion asymmetries presented here sample an x range of similar to 0.03-0.16 and provide unique information on the sign of the gluon-helicity distribution.
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| 5. |
- Adare, A., et al.
(author)
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Cross section for b(b)over-bar production via dielectrons in d plus Au collisions at root s(NN)=200 GeV
- 2015
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In: Physical Review C (Nuclear Physics). - 0556-2813. ; 91:1
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Journal article (peer-reviewed)abstract
- We report a measurement of e(+)e(-) pairs from semileptonic heavy-flavor decays in d + Au collisions at root s(NN) = 200 GeV. By exploring the mass and transverse-momentum dependence of the yield, the bottom decay contribution can be isolated from charm, and quantified by comparison to PYTHIA and MC@NLO simulations. The resulting b (b) over bar -production cross section is sigma(dAu)(b (b) over bar) = 1.37 +/- 0.28 (stat) +/- 0.46 (syst) mb, which is equivalent to a nucleon-nucleon cross section of sigma(NN)(b (b) over bar) = 3.4 +/- 0.8 (stat) +/- 1.1 ( syst) mu b.
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| 6. |
- Adare, A., et al.
(author)
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Heavy-quark production and elliptic flow in Au plus Au collisions at root(NN)-N-S=62.4 GeV
- 2015
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In: Physical Review C (Nuclear Physics). - 0556-2813. ; 91:4
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Journal article (peer-reviewed)abstract
- We present measurements of electrons and positrons from the semileptonic decays of heavy-flavor hadrons at midrapidity (vertical bar gamma vertical bar < 0.35) in Au + Au collisions at root(NN)-N-S = 62.4 GeV. The data were collected in 2010 by the PHENIX experiment that included the new hadron-blind detector. The invariant yield of electrons from heavy-flavor decays is measured as a function of transverse momentum in the range 1 < p(T)(e) < 5 GeV/c. The invariant yield per binary collision is slightly enhanced above the p + p reference in Au + Au 0%-20%, 20%-40%, and 40%-60% centralities at a comparable level. At this low beam energy this may be a result of the interplay between initial-state Cronin effects, final-state flow, and energy loss in medium. The v(2) of electrons from heavy-flavor decays is nonzero when averaged between 1.3 < p(T)(e) < 2.5 GeV/c for 0%-40% centrality collisions at root(NN)-N-S = 62.4 GeV. For 20%-40% centrality collisions, the v(2) at root(NN)-N-S = 62.4 GeV is smaller than that for heavy-flavor decays at root(NN)-N-S = 200 GeV. The v2 of the electrons from heavy-flavor decay at the lower beam energy is also smaller than v(2) for pions. Both results indicate that the heavy quarks interact with the medium formed in these collisions, but they may not be at the same level of thermalization with the medium as observed at root(NN)-N-S = 200 GeV.
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| 7. |
- Adare, A., et al.
(author)
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Lévy-stable two-pion Bose-Einstein correlations in s NN =200 GeV Au+Au collisions
- 2018
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In: Physical Review C. - 2469-9985. ; 97:6
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Journal article (peer-reviewed)abstract
- We present a detailed measurement of charged two-pion correlation functions in 0-30% centrality sNN=200 GeV Au+Au collisions by the PHENIX experiment at the Relativistic Heavy Ion Collider. The data are well described by Bose-Einstein correlation functions stemming from Lévy-stable source distributions. Using a fine transverse momentum binning, we extract the correlation strength parameter λ, the Lévy index of stability α, and the Lévy length scale parameter R as a function of average transverse mass of the pair mT. We find that the positively and the negatively charged pion pairs yield consistent results, and their correlation functions are represented, within uncertainties, by the same Lévy-stable source functions. The λ(mT) measurements indicate a decrease of the strength of the correlations at low mT. The Lévy length scale parameter R(mT) decreases with increasing mT, following a hydrodynamically predicted type of scaling behavior. The values of the Lévy index of stability α are found to be significantly lower than the Gaussian case of α=2, but also significantly larger than the conjectured value that may characterize the critical point of a second-order quark-hadron phase transition. © 2018 American Physical Society.
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| 8. |
- Adare, A., et al.
(author)
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Low-momentum direct-photon measurement in Cu + Cu collisions at sNN =200 GeV
- 2018
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In: Physical Review C. - 2469-9985. ; 98:5
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Journal article (peer-reviewed)abstract
- We measured direct photons for pT<5GeV/c in minimum bias and 0%–40% most-central events at midrapidity for Cu+Cu collisions at √sNN=200GeV. The e+e− contribution from quasireal direct virtual photons has been determined as an excess over the known hadronic contributions in the e+e− mass distribution. A clear enhancement of photons over the binary scaled p+p fit is observed for pT<4GeV/c in Cu+Cu data. The pT spectra are consistent with the Au+Au data covering a similar number of participants. The inverse slopes of the exponential fits to the excess after subtraction of the p+p baseline are 285±53(stat)±57(syst)MeV/c and 333±72(stat)±45(syst)MeV/c for minimum bias and 0%–40% most-central events, respectively. The rapidity density, dN/dy, of photons demonstrates the same power law as a function of dNch/dη observed in Au+Au at the same collision energy.
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| 9. |
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| 10. |
- Adare, A., et al.
(author)
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Measurement of gamma(1S+2S+3S) production in p plus p and Au plus Au collisions at root sNN=200 GeV
- 2015
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In: Physical Review C (Nuclear Physics). - 0556-2813. ; 91:2
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Journal article (peer-reviewed)abstract
- Measurements of bottomonium production in heavy-ion and p + p collisions at the Relativistic Heavy Ion Collider (RHIC) are presented. The inclusive yield of the three states, (1S + 2S + 3S), was measured in the PHENIX experiment via electron-positron decay pairs at midrapidity for Au + Au and p + p collisions at root sNN = 200 GeV. The (1S + 2S + 3S) -> e(+)e(-) differential cross section at midrapidity was found to be B(ee)d sigma/dy = 108 +/- 38 (stat) +/- 15 (syst) +/- 11 (luminosity) pb in p + p collisions. The nuclear modification factor in the 30% most central Au + Au collisions indicates a suppression of the total. state yield relative to the extrapolation from p + p collision data. The suppression is consistent with measurements made by STAR at RHIC and at higher energies by the CMS experiment at the Large Hadron Collider.
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