| 1. |
- Adare, A., et al.
(author)
-
Measurement of K-S(0) and K*(0) in p plus p, d plus Au, and Cu plus Cu collisions at root s(NN)=200 GeV
- 2014
-
In: Physical Review C (Nuclear Physics). - 0556-2813. ; 90:5
-
Journal article (peer-reviewed)abstract
- The PHENIX experiment at the Relativistic Heavy Ion Collider has performed a systematic study of K-S(0) and K*(0) meson production at midrapidity in p + p, d + Au, and Cu + Cu collisions at root s(NN) = 200 GeV. The K-S(0) and K*(0) mesons are reconstructed via their K-S(0) -> pi(0)(-> gamma gamma) pi(0)(-> gamma gamma) and K*(0) -> K-+/-pi(-/+) decay modes, respectively. The measured transverse-momentum spectra are used to determine the nuclear modification factor of K-S(0) and K*(0) mesons in d + Au and Cu + Cu collisions at different centralities. In the d + Au collisions, the nuclear modification factor of K-S(0) and K*(0) mesons is almost constant as a function of transverse momentum and is consistent with unity, showing that cold-nuclear-matter effects do not play a significant role in the measured kinematic range. In Cu + Cu collisions, within the uncertainties no nuclear modification is registered in peripheral collisions. In central collisions, both mesons show suppression relative to the expectations from the p + p yield scaled by the number of binary nucleon-nucleon collisions in the Cu + Cu system. In the p(T) range 2-5 GeV/c, the strange mesons (K-S(0), K*(0)) similarly to the phi meson with hidden strangeness, showan intermediate suppression between the more suppressed light quark mesons (pi(0)) and the nonsuppressed baryons (p, (p) over bar). At higher transverse momentum, p(T) > 5 GeV/c, production of all particles is similarly suppressed by a factor of approximate to 2.
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| 2. |
- Adare, A., et al.
(author)
-
Production of omega mesons in p plus p, d plus Au, Cu plus Cu, and Au plus Au collisions at root s(NN)=200 GeV
- 2011
-
In: Physical Review C (Nuclear Physics). - 0556-2813. ; 84:4
-
Journal article (peer-reviewed)abstract
- The PHENIX experiment at the Relativistic Heavy Ion Collider has measured omega meson production via leptonic and hadronic decay channels in p + p, d + Au, Cu+ Cu, and Au + Au collisions at root s(NN) = 200 GeV. The invariant transverse momentum spectra measured in different decay modes give consistent results. Measurements in the hadronic decay channel in Cu Cu and Au + Au collisions show that. production has a suppression pattern at high transverse momentum, similar to that of pi(0) and eta in central collisions, but no suppression is observed in peripheral collisions. The nuclear modification factors, R-AA, are consistent in Cu + Cu and Au + Au collisions at similar numbers of participant nucleons.
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| 3. |
- Adare, A., et al.
(author)
-
Direct photon production in d+Au collisions at root s(NN)=200 GeV
- 2013
-
In: Physical Review C (Nuclear Physics). - 0556-2813. ; 87:5
-
Journal article (peer-reviewed)abstract
- Direct photons have been measured in root s(NN) = 200 GeV d + Au collisions at midrapidity. A wide p(T) range is covered by measurements of nearly real virtual photons (1 < p(T) < 6 GeV/c) and real photons (5 < p(T) < 16 GeV/c). The invariant yield of the direct photons in d + Au collisions over the scaled p + p cross section is consistent with unity. Theoretical calculations assuming standard cold-nuclear-matter effects describe the data well for the entire p(T) range. This indicates that the large enhancement of direct photons observed in Au + Au collisions for 1.0 < p(T) < 2.5 GeV/c is attributable to a source other than the initial-state nuclear effects.
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| 4. |
- Adare, A., et al.
(author)
-
Nuclear modification factors of phi mesons in d plus Au, Cu plus Cu, and Au plus Au collisions at root s(NN)=200 GeV
- 2011
-
In: Physical Review C (Nuclear Physics). - 0556-2813. ; 83:2
-
Journal article (peer-reviewed)abstract
- The PHENIX experiment at the Relativistic Heavy Ion Collider has performed systematic measurements of phi meson production in the K+K- decay channel at midrapidity in p + p, d + Au, Cu + Cu, and Au + Au collisions at root s(NN) = 200 GeV. Results are presented on the phi invariant yield and the nuclear modification factor R-AA for Au + Au and Cu + Cu, and R-dA for d + Au collisions, studied as a function of transverse momentum (1 < p(T) < 7 GeV/c) and centrality. In central and midcentral Au + Au collisions, the R-AA of phi exhibits a suppression relative to expectations from binary scaled p + p results. The amount of suppression is smaller than that of the pi(0) and the. in the intermediate p(T) range (2-5 GeV/c), whereas, at higher p(T), the phi, pi(0), and. show similar suppression. The baryon (proton and antiproton) excess observed in central Au + Au collisions at intermediate p(T) is not observed for the phi meson despite the similar masses of the proton and the phi. This suggests that the excess is linked to the number of valence quarks in the hadron rather than its mass. The difference gradually disappears with decreasing centrality, and, for peripheral collisions, the R-AA values for both particle species are consistent with binary scaling. Cu + Cu collisions show the same yield and suppression as Au + Au collisions for the same number of N-part. The R-dA of phi shows no evidence for cold nuclear effects within uncertainties.
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| 5. |
- Adare, A., et al.
(author)
-
Medium Modification of Jet Fragmentation in Au plus Au Collisions at root S-NN=200 GeV Measured in Direct Photon-Hadron Correlations
- 2013
-
In: Physical Review Letters. - 1079-7114. ; 111:3
-
Journal article (peer-reviewed)abstract
- The jet fragmentation function is measured with direct photon-hadron correlations in p + p and Au + Au collisions at root S-NN = 200 GeV. The P-T of the photon is an excellent approximation to the initial P-T of the jet and the ratio Z(T) = P-T(h)/P-T(gamma) is used as a proxy for the jet fragmentation function. A statistical subtraction is used to extract the direct photon-hadron yields in Au + Au collisions while a photon isolation cut is applied in p + p. I-AA, the ratio of hadron yield opposite the photon in Au + Au to that in p + p, indicates modification of the jet fragmentation function. Suppression, most likely due to energy loss in the medium, is seen at high Z(T). The associated hadron yield at low Z(T) is enhanced at large angles. Such a trend is expected from redistribution of the lost energy into increased production of low-momentum particles.
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| 6. |
- Adare, A., et al.
(author)
-
Cross section and transverse single-spin asymmetry of eta mesons in p up arrow plus p collisions at root s=200 GeV at forward rapidity
- 2014
-
In: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 90:7
-
Journal article (peer-reviewed)abstract
- We present a measurement of the cross section and transverse single-spin asymmetry (AN) for. mesons at large pseudorapidity from root s = 200 GeV p up arrow + p collisions. The measured cross section for 0.5 < p(T) < 5.0 GeV/c and 3.0 < vertical bar eta vertical bar < 3.8 is well described by a next-to-leading-order perturbative-quantum-chromodynamics calculation. The asymmetries A(N) have been measured as a function of Feynman-x (x(F)) from 0.2 < vertical bar x(F)vertical bar < 0.7, as well as transverse momentum (p(T)) from 1.0 < p(T) < 4.5 GeV/c. The asymmetry averaged over positive x(F) is < A(N)> = 0.061 +/- 0.014. The results are consistent with prior transverse single-spin measurements of forward eta and pi(0) mesons at various energies in overlapping x(F) ranges. Comparison of different particle species can help to determine the origin of the large observed asymmetries in p up arrow + p collisions.
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| 7. |
- Adare, A., et al.
(author)
-
gamma (1S+2S+3S) production in d plus Au and p plus p collisions at root s(NN)=200 GeV and cold-nuclear-matter effects
- 2013
-
In: Physical Review C (Nuclear Physics). - 0556-2813. ; 87:4
-
Journal article (peer-reviewed)abstract
- The three gamma states, gamma (1S + 2S + 3S), are measured in d + Au and p + p collisions at root s(NN) = 200 GeV and rapidities 1.2 < vertical bar y vertical bar < 2.2 by the PHENIX experiment at the Relativistic Heavy Ion Collider. Cross sections for the inclusive gamma (1S + 2S + 3S) production are obtained. The inclusive yields per binary collision for d + Au collisions relative to those in p + p collisions (R-dAu) are found to be 0.62 +/- 0.26 (stat) +/- 0.13 (syst) in the gold-going direction and 0.91 +/- 0.33 (stat) +/- 0.16 (syst) in the deuteron-going direction. The measured results are compared to a nuclear-shadowing model, EPS09 [Eskola et al., J. High Energy Phys. 04 (2009) 065], combined with a final-state breakup cross section, sigma(br), and compared to lower energy p + A results. We also compare the results to the PHENIX J/psi results [Adare et al., Phys. Rev. Lett. 107, 142301 (2011)]. The rapidity dependence of the observed gamma suppression is consistent with lower energy p + A measurements. DOI: 10.1103/PhysRevC.87.044909
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| 8. |
- Adare, A., et al.
(author)
-
Low-mass vector-meson production at forward rapidity in p plus p collisions at root s=200 GeV
- 2014
-
In: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 90:5
-
Journal article (peer-reviewed)abstract
- The PHENIX experiment at the Relativistic Heavy Ion Collider has measured low-mass vector-meson ,omega, rho, and phi, production through the dimuon decay channel at forward rapidity (1.2 < vertical bar y vertical bar < 2.2) in p + p collisions at root s = 200 GeV. The differential cross sections for these mesons are measured as a function of both p(T) and rapidity. We also report the integrated differential cross sections over 1 < p(T) < 7 GeV/c and 1.2 < vertical bar y vertical bar < 2.2: d sigma/dy(omega + rho rho -> mu mu) = 80 +/- 6(stat) +/- 12(syst)nb and d sigma/dy(phi -> mu mu) = 27 +/- 3(stat) +/- 4(syst)nb. These results are compared with midrapidity measurements and calculations.
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| 9. |
- Adare, A., et al.
(author)
-
Azimuthal correlations of electrons from heavy-flavor decay with hadrons in p plus p and Au plus Au collisions at root s(NN)=200 GeV
- 2011
-
In: Physical Review C (Nuclear Physics). - 0556-2813. ; 83:4
-
Journal article (peer-reviewed)abstract
- Measurements of electrons from the decay of open-heavy-flavor mesons have shown that the yields are suppressed in Au+Au collisions compared to expectations from binary-scaled p+p collisions. These measurements indicate that charm and bottom quarks interact with the hot dense matter produced in heavy-ion collisions much more than expected. Here we extend these studies to two-particle correlations where one particle is an electron from the decay of a heavy-flavor meson and the other is a charged hadron from either the decay of the heavy meson or from jet fragmentation. These measurements provide more detailed information about the interactions between heavy quarks and the matter, such as whether the modification of the away-side-jet shape seen in hadron-hadron correlations is present when the trigger particle is from heavy-meson decay and whether the overall level of away-side-jet suppression is consistent. We statistically subtract correlations of electrons arising from background sources from the inclusive electron-hadron correlations and obtain two-particle azimuthal correlations at root s(NN) = 200 GeV between electrons from heavy-flavor decay with charged hadrons in p+p and also first results in Au+Au collisions. We find the away-side-jet shape and yield to be modified in Au+Au collisions compared to p+p collisions.
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| 10. |
- Adare, A., et al.
(author)
-
Cold Nuclear Matter Effects on J/psi Yields as a Function of Rapidity and Nuclear Geometry in d plus A Collisions at root S-NN=200 GeV
- 2011
-
In: Physical Review Letters. - 1079-7114. ; 107:14
-
Journal article (peer-reviewed)abstract
- We present measurements of J/psi yields in d + Au collisions at root S-NN = 200 GeV recorded by the PHENIX experiment and compare them with yields in p + p collisions at the same energy per nucleon-nucleon collision. The measurements cover a large kinematic range in J/psi rapidity (-2.2 < y < 2.4) with high statistical precision and are compared with two theoretical models: one with nuclear shadowing combined with final state breakup and one with coherent gluon saturation effects. In order to remove model dependent systematic uncertainties we also compare the data to a simple geometric model. The forward rapidity data are inconsistent with nuclear modifications that are linear or exponential in the density weighted longitudinal thickness, such as those from the final state breakup of the bound state.
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| 11. |
- Adare, A., et al.
(author)
-
Ground and excited state charmonium production in p plus p collisions at root s=200 GeV
- 2012
-
In: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 85:9
-
Journal article (peer-reviewed)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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| 12. |
- Adare, A., et al.
(author)
-
Heavy-flavor electron-muon correlations in p plus p and d plus Au collisions at root s(NN)=200 GeV
- 2014
-
In: Physical Review C (Nuclear Physics). - 0556-2813. ; 89:3
-
Journal article (peer-reviewed)abstract
- Background: Heavy-flavor modification in relativistic p(d) + A collisions are sensitive to different kinds of strong-interaction physics ranging from modifications of the nuclear wave function to initial- and final-state energy loss. Modifications to single heavy-flavor particles and their decay leptons at midrapidity and forward rapidity are well established at the Relativistic Heavy Ion Collider (RHIC). Purpose: This paper presents measurements of azimuthal correlations of electron-muon pairs produced from heavy-flavor decays, primarily c (c) over bar, in root s(NN) = 200 GeV p + p and d + Au collision using the PHENIX detector at RHIC. The electrons are measured at midrapidity while the muons in the pair are measured at forward rapidity, defined as the direction of the deuteron beam, in order to utilize the deuteron to probe low-x partons in the gold nucleus. Methods: This analysis uses the central spectrometer arms for electron identification and forward spectrometer arms for muon identification. Azimuthal correlations are built in all sign combinations for e-mu pairs. Subtracting the like-sign yield from the unlike-sign yield removes the correlations from light flavor decays and conversions. Results: Comparing the p + p results with several different Monte Carlo event generators, we find the results are consistent with a total charm cross section sigma(c (c) over bar) = 538 +/- 46 (stat) +/- 197 (data syst) +/- 174 (model syst) mu b. These generators also indicate that the back-to-back peak at Delta phi = pi is dominantly from the leading-order contributions (gluon fusion), while higher-order processes (flavor excitation and gluon splitting) contribute to the yield at all Delta phi. We observe a suppression in the pair yield per collision in d + Au. We find the pair yield suppression factor for 2.7 < Delta phi < 3.2 rad is J(dA) = 0.433 +/- 0.087 (stat) +/- 0.135 (syst). Conclusions: The e-mu pairs result from partons at x(Au) similar to 10(-2) at Q(2) = 10 GeV/c(2) at the edge of the shadowing region. The pair suppression indicates modification to c (c) over bar pairs for these kinematics in the cold nuclear medium at RHIC.
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| 13. |
- Adare, A., et al.
(author)
-
Measurement of transverse single-spin asymmetries for J/psi production in polarized p plus p collisions at root s=200 GeV
- 2010
-
In: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 82:11
-
Journal article (peer-reviewed)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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| 14. |
- Adare, A., et al.
(author)
-
Measurement of transverse-single-spin asymmetries for midrapidity and forward-rapidity production of hadrons in polarized p plus p collisions at root s=200 and 62.4 GeV
- 2014
-
In: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 90:1
-
Journal article (peer-reviewed)abstract
- Measurements of transverse-single-spin asymmetries (A(N)) in p + p collisions at root s = 62.4 and 200 GeV with the PHENIX detector at the Relativistic Heavy Ion Collider are presented. At midrapidity, A(N) is measured for neutral pion and eta mesons reconstructed from diphoton decay, and, at forward rapidities, neutral pions are measured using both diphotons and electromagnetic clusters. The neutral-pion measurement of A(N) at midrapidity is consistent with zero with uncertainties a factor of 20 smaller than previous publications, which will lead to improved constraints on the gluon Sivers function. At higher rapidities, where the valence quark distributions are probed, the data exhibit sizable asymmetries. In comparison with previous measurements in this kinematic region, the new data extend the kinematic coverage in root s and p(T), and it is found that the asymmetries depend only weakly on root s. The origin of the forward A(N) is presently not understood quantitatively. The extended reach to higher p(T) probes the transition between transverse momentum dependent effects at low p(T) and multiparton dynamics at high p(T).
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| 15. |
- Adare, A., et al.
(author)
-
Suppression of away-side jet fragments with respect to the reaction plane in Au plus Au collisions at root s(NN)=200 GeV
- 2011
-
In: Physical Review C (Nuclear Physics). - 0556-2813. ; 84:2
-
Journal article (peer-reviewed)abstract
- Pair correlations between large transverse momentum neutral pion triggers (p(T) = 4-7 GeV/c) and charged hadron partners (p(T) = 3-7 GeV/c) in central (0%-20%) and midcentral (20%-60%) Au + Au collisions at root s(NN) = 200 GeV are presented as a function of trigger orientation with respect to the reaction plane. The particles are at larger momentum than where jet shape modifications have been observed, and the correlations are sensitive to the energy loss of partons traveling through hot densematter. An out-of-plane trigger particle produces only 26 +/- 20% of the away-side pairs that are observed opposite of an in-plane trigger particle for midcentral (20%-60%) collisions. In contrast, near-side jet fragments are consistent with no suppression or dependence on trigger orientation with respect to the reaction plane. These observations are qualitatively consistent with a picture of little near-side parton energy loss either due to surface bias or fluctuations and increased away-side parton energy loss due to a long path through the medium. The away-side suppression as a function of reaction-plane angle is shown to be sensitive to both the energy loss mechanism and the space-time evolution of heavy-ion collisions.
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| 16. |
- Adare, A., et al.
(author)
-
Transition in Yield and Azimuthal Shape Modification in Dihadron Correlations in Relativistic Heavy Ion Collisions
- 2010
-
In: Physical Review Letters. - 1079-7114. ; 104:25
-
Journal article (peer-reviewed)abstract
- Hard-scattered parton probes produced in collisions of large nuclei indicate large partonic energy loss, possibly with collective produced-medium response to the lost energy. We present measurements of pi(0) trigger particles at transverse momenta p(T)(t) = 4-12 GeV/c and associated charged hadrons (p(T)(a) = 0.5-7 GeV/c) vs relative azimuthal angle Delta phi in Au + Au and p + p collisions at root s(NN) = 200 GeV. The Au + Au distribution at low p(T)(a), whose shape has been interpreted as a medium effect, is modified for p(T)(t) < 7 GeV/c. At higher p(T)(t), the data are consistent with unmodified or very weakly modified shapes, even for the lowest measured p(T)(a), which quantitatively challenges some medium response models. The associated yield of hadrons opposing the trigger particle in Au + Au relative to p + p (I-AA) is suppressed at high p(T) (I-AA approximate to 0.35-0.5), but less than for inclusive suppression (R-AA approximate to 0.2).
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| 17. |
- Adare, A., et al.
(author)
-
Transverse momentum dependence of eta meson suppression in Au plus Au collisions at root s(NN)=200 GeV
- 2010
-
In: Physical Review C (Nuclear Physics). - 0556-2813. ; 82:1
-
Journal article (peer-reviewed)abstract
- New measurements by the PHENIX experiment at the Relativistic Heavy Ion Collider for. production at midrapidity as a function of transverse momentum ((PT)) and collision centrality in root s(NN) = 200 GeV Au + Au and p + p collisions are presented. They indicate nuclear modification factors (R-AA) which are similar in both magnitude and trend to those found in earlier pi(0) measurements. Linear fits to R-AA as a function of (PT) in 5-20 GeV/c show that the slope is consistent with zero within two standard deviations at all centralities, although a slow rise cannot be excluded. Having different statistical and systematic uncertainties, the pi(0) and eta measurements are complementary at high (PT); thus, along with the extended (PT) range of these data they can provide additional constraints for theoretical modeling and the extraction of transport properties.
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| 18. |
- Klionsky, Daniel J., et al.
(author)
-
Guidelines for the use and interpretation of assays for monitoring autophagy
- 2012
-
In: Autophagy. - : Informa UK Limited. - 1554-8635 .- 1554-8627. ; 8:4, s. 445-544
-
Research review (peer-reviewed)abstract
- In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. A key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process vs. those that measure flux through the autophagy pathway (i.e., the complete process); thus, a block in macroautophagy that results in autophagosome accumulation needs to be differentiated from stimuli that result in increased autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular autophagy assays, we hope to encourage technical innovation in the field.
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| 19. |
- Adare, A., et al.
(author)
-
Cold-Nuclear-Matter Effects on Heavy-Quark Production at Forward and Backward Rapidity in d + Au Collisions at root s(NN) = GeV
- 2014
-
In: Physical Review Letters. - 1079-7114. ; 112:25
-
Journal article (peer-reviewed)abstract
- The PHENIX experiment has measured open heavy-flavor production via semileptonic decay over the transverse momentum range 1 < p(T) < 6 GeV/c at forward and backward rapidity (1.4 < vertical bar y vertical bar < 2.0) in d + Au and p + p collisions at root s(NN) = 200 GeV. In central d + Au collisions, relative to the yield in p + p collisions scaled by the number of binary nucleon-nucleon collisions, a suppression is observed at forward rapidity (in the d-going direction) and an enhancement at backward rapidity (in the Au-going direction). Predictions using nuclear-modified-parton-distribution functions, even with additional nuclear-p(T) broadening, cannot simultaneously reproduce the data at both rapidity ranges, which implies that these models are incomplete and suggests the possible importance of final-state interactions in the asymmetric d + Au collision system. These results can be used to probe cold-nuclear-matter effects, which may significantly affect heavy-quark production, in addition to helping constrain the magnitude of charmonia-breakup effects in nuclear matter.
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| 20. |
- Adare, A., et al.
(author)
-
Nuclear matter effects on J/psi production in asymmetric Cu plus Au collisions at root S-NN=200 GeV
- 2014
-
In: Physical Review C (Nuclear Physics). - 0556-2813. ; 90:6
-
Journal article (peer-reviewed)abstract
- We report on J/psi production from asymmetric Cu + Au heavy-ion collisions at root S-NN = 200 GeV at the Relativistic Heavy Ion Collider at both forward (Cu-going direction) and backward (Au-going direction) rapidities. The nuclear modification of J/psi yields in Cu + Au collisions in the Au-going direction is found to be comparable to that inAu + Au collisions when plotted as a function of the number of participating nucleons. In the Cu-going direction, J/psi production shows a stronger suppression. This difference is comparable in magnitude and has the same sign as the difference expected from shadowing effects due to stronger low-x gluon suppression in the larger Au nucleus.
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| 21. |
- Adare, A., et al.
(author)
-
Spectra and ratios of identified particles in Au plus Au and d plus Au collisions at root s(NN)=200 GeV
- 2013
-
In: Physical Review C (Nuclear Physics). - 0556-2813. ; 88:2
-
Journal article (peer-reviewed)abstract
- The transverse momentum (p(T)) spectra and ratios of identified charged hadrons (pi(+/-), K-+/-, p, (p) over bar) produced in root s(NN) = 200 GeV Au + Au and d + Au collisions are reported in five different centrality classes for each collision species. The measurements of pions and protons are reported up to p(T) = 6 GeV/c (5 GeV/c), and the measurements of kaons are reported up to p(T) = 4 GeV/c (3.5 GeV/c) in Au + Au (d + Au) collisions. In the intermediate p(T) region, between 2 and 5 GeV/c, a significant enhancement of baryon-to-meson ratios compared to those measured in p + p collisions is observed. This enhancement is present in both Au + Au and d + Au collisions and increases as the collisions become more central. We compare a class of peripheral Au + Au collisions with a class of central d + Au collisions which have a comparable number of participating nucleons and binary nucleon-nucleon collisions. The p(T)-dependent particle ratios for these classes display a remarkable similarity, which is then discussed.
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| 22. |
- Adare, A., et al.
(author)
-
Centrality categorization Rp(d)+A in high-energy collisions
- 2014
-
In: Physical Review C (Nuclear Physics). - 0556-2813. ; 90:3
-
Journal article (peer-reviewed)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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| 23. |
- Adare, A., et al.
(author)
-
Cold-Nuclear-Matter Effects on Heavy-Quark Production in d+Au Collisions at root S-NN=200 GeV
- 2012
-
In: Physical Review Letters. - 1079-7114. ; 109:24
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Journal article (peer-reviewed)abstract
- The PHENIX experiment has measured electrons and positrons at midrapidity from the decays of hadrons containing charm and bottom quarks produced in d + Au and p + p collisions at root S-NN = 200 GeV in the transverse-momentum range 0.85 <= p(T)(e) <= 8.5 GeV/c. In central d + Au collisions, the nuclear modification factor R-dA at 1.5 < p(T) < 5 GeV/c displays evidence of enhancement of these electrons, relative to those produced in p + p collisions, and shows that the mass-dependent Cronin enhancement observed at the Relativistic Heavy Ion Collider extends to the heavy D meson family. A comparison with the neutral-pion data suggests that the difference in cold-nuclear-matter effects on light- and heavy-flavor mesons could contribute to the observed differences between the pi(0) and heavy-flavor-electron nuclear modification factors R-AA. DOI: 10.1103/PhysRevLett.109.242301
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| 24. |
- Adare, A., et al.
(author)
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Inclusive double-helicity asymmetries in neutral-pion and eta-meson production in + collisions at root s=200 GeV
- 2014
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In: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 90:1
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Journal article (peer-reviewed)abstract
- Results are presented from data recorded in 2009 by the PHENIX experiment at the Relativistic Heavy Ion Collider for the double-longitudinal spin asymmetry, A(LL), for pi(0) and eta production in root s = 200 GeV polarized p + p collisions. Comparison of the pi(0) results with different theory expectations based on fits of other published data showed a preference for small positive values of gluon polarization, Delta G, in the proton in the probed Bjorken x range. The effect of adding the new 2009 pi(0) data to a recent global analysis of polarized scattering data is also shown, resulting in a best fit Delta G(DSSV)([0.05,0.2]) = 0.06(-0.15)(+0.11) in the range 0.05 < x < 0.2, with the uncertainty at Delta chi(2) = 9 when considering only statistical experimental uncertainties. Shifting the PHENIX data points by their systematic uncertainty leads to a variation of the best-fit value of Delta G(DSSV)([0.05,0.2]) between 0.02 and 0.12, demonstrating the need for full treatment of the experimental systematic uncertainties in future global analyses.
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| 25. |
- Adare, A., et al.
(author)
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Nuclear Modification of psi ', chi(c), and J/psi Production in d plus Au Collisions at root s(NN)=200 GeV
- 2013
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In: Physical Review Letters. - 1079-7114. ; 111:20
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Journal article (peer-reviewed)abstract
- We present results for three charmonia states (psi' chi(c), and J/ psi) in d + Au collisions at vertical bar y vertical bar < 0.35 and root s(NN) = 200 GeV. We find that the modification of the psi' yield relative to that of the J/ psi scales approximately with charged particle multiplicity at midrapidity across p + A, d + Au, and A + A results from the Super Proton Synchrotron and the Relativistic Heavy Ion Collider. In large-impact-parameter collisions we observe a similar suppression for the psi' and J/ psi, while in small-impact-parameter collisions the more weakly bound psi' is more strongly suppressed. Owing to the short time spent traversing the Au nucleus, the larger psi' suppression in central events is not explained by an increase of the nuclear absorption owing to meson formation time effects.
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