| 31. |
- Adare, A., et al.
(författare)
-
Measurement of transverse single-spin asymmetries for J/psi production in polarized p plus p collisions at root s=200 GeV
- 2010
-
Ingår i: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 82:11
-
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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| 32. |
- Adare, A., et al.
(författare)
-
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
-
Ingår i: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 90:1
-
Tidskriftsartikel (refereegranskat)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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| 33. |
- Adare, A., et al.
(författare)
-
Spectra and ratios of identified particles in Au plus Au and d plus Au collisions at root s(NN)=200 GeV
- 2013
-
Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 88:2
-
Tidskriftsartikel (refereegranskat)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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| 34. |
- Adare, A., et al.
(författare)
-
Systematic study of charged-pion and kaon femtoscopy in Au plus Au collisions at root s(NN)=200 GeV
- 2015
-
Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 92:3
-
Tidskriftsartikel (refereegranskat)abstract
- We present a systematic study of charged-pion and kaon interferometry in Au + Au collisions at root s(NN) = 200 GeV. The kaon mean source radii are found to be larger than pion radii in the outward and longitudinal directions for the same transverse mass; this difference increases for more central collisions. The azimuthal-angle dependence of the radii was measured with respect to the second-order event plane and similar oscillations of the source radii were found for pions and kaons. Hydrodynamic models qualitatively describe the similar oscillations of the mean source radii for pions and kaons, but they do not fully describe the transverse-mass dependence of the oscillations.
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| 35. |
- Adler, S. S., et al.
(författare)
-
Azimuthal angle correlations for rapidity separated hadron pairs in d+Au collisions at root s(NN)=200 GeV
- 2006
-
Ingår i: Physical Review Letters. - 1079-7114. ; 96:22
-
Tidskriftsartikel (refereegranskat)abstract
- Deuteron-gold (d+Au) collisions at the Relativistic Heavy Ion Collider provide ideal platforms for testing QCD theories in dense nuclear matter at high energy. In particular, models suggesting strong saturation effects for partons carrying small nucleon momentum fraction (x) predict modifications to jet production at forward rapidity (deuteron-going direction) in d+Au collisions. We report on two-particle azimuthal angle correlations between charged hadrons at forward/backward (deuteron/gold going direction) rapidity and charged hadrons at midrapidity in d+Au and p+p collisions at root s(NN)=200 GeV. Jet structures observed in the correlations are quantified in terms of the conditional yield and angular width of away-side partners. The kinematic region studied here samples partons in the gold nucleus with x similar to 0.1 to similar to 0.01. Within this range, we find no x dependence of the jet structure in d+Au collisions.
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| 36. |
- Adler, S. S., et al.
(författare)
-
Centrality dependence of charged hadron production in deuteron plus gold and nucleon plus gold collisions at root S-NN=200 GeV
- 2008
-
Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 77:1
-
Tidskriftsartikel (refereegranskat)abstract
- We present transverse momentum (p(T)) spectra of charged hadrons measured in deuteron-gold and nucleon-gold collisions at root s(NN)=200 GeV for four centrality classes. Nucleon-gold collisions were selected by tagging events in which a spectator nucleon was observed in one of two forward rapidity detectors. The spectra and yields were investigated as a function of the number of binary nucleon-nucleon collisions, nu, suffered by deuteron nucleons. A comparison of charged particle yields to those in p+p collisions show that yield per nucleon-nucleon collision saturates with nu for high momentum particles. We also present the charged hadron to neutral pion ratios as a function of p(T).
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| 37. |
- Adler, S. S., et al.
(författare)
-
Centrality dependence of pi(0) and eta production at large transverse momentum in root s(NN) = 200 GeV d+Au collisions
- 2007
-
Ingår i: Physical Review Letters. - 1079-7114. ; 98:17
-
Tidskriftsartikel (refereegranskat)abstract
- The dependence of transverse momentum spectra of neutral pions and eta mesons with p(T) < 16 GeV/c and p(T) < 12 GeV/c, respectively, on the centrality of the collision has been measured at midrapidity by the PHENIX experiment at the BNL Relativistic Heavy Ion Collider (RHIC) in d + Au collisions at root s(NN) = 200 GeV. The measured yields are compared to those in p + p collisions at the same root s(NN) scaled by the number of underlying nucleon-nucleon collisions in d + Au. At all centralities, the yield ratios show no suppression, in contrast to the strong suppression seen for central An + Au collisions at RHIC. Only a weak p(T) and centrality dependence can be observed.
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| 38. |
- Adler, S. S., et al.
(författare)
-
High transverse momentum eta meson production in p+p, d+Au, and Au+Au collisions at root s(NN)=200 GeV
- 2007
-
Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 75:2
-
Forskningsöversikt (refereegranskat)abstract
- Inclusive transverse momentum spectra of eta mesons in the range p(T)approximate to 2-12 GeV/c have been measured at midrapidity (vertical bar eta vertical bar < 0.35) by the PHENIX experiment at RHIC in p+p,d+Au, and Au+Au collisions at root s(NN)=200 GeV. The eta mesons are reconstructed through their eta ->gamma gamma channel for the three colliding systems as well as through the eta ->pi(0)pi(+)pi(-) decay mode in p+p and d+Au collisions. The nuclear modification factor in d+Au collisions, R-dAu(p(T))approximate to 1.0-1.1, suggests at most only modest p(T) broadening ("Cronin enhancement"). In central Au+Au reactions, the eta yields are significantly suppressed, with R-AuAu(p(T))approximate to 0.2. The ratio of eta to pi(0) yields is approximately constant as a function of p(T) for the three colliding systems in agreement with the high-p(T) world average of R-eta/pi(0)approximate to 0.5 in hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions for a wide range of center-of-mass energies (root sNN approximate to 3-1800 GeV) as well as, for high scaled momentum x(p), in e(+)e(-) annihilations at root s=91.2 GeV. These results are consistent with a scenario where high-p(T) eta production in nuclear collisions at the Relativistic Heavy Ion Collider is largely unaffected by initial-state effects but where light-quark mesons (pi(0),eta) are equally suppressed due to final-state interactions of the parent partons in the dense medium produced in Au+Au reactions.
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| 39. |
- Adler, S. S., et al.
(författare)
-
Jet properties from dihadron correlations in p plus p collisions at root s=200 GeV
- 2006
-
Ingår i: Physical Review D (Particles, Fields, Gravitation and Cosmology). - 1550-2368. ; 74:7
-
Tidskriftsartikel (refereegranskat)abstract
- The properties of jets produced in p+p collisions at root s=200 GeV are measured using the method of two-particle correlations. The trigger particle is a leading particle from a large transverse momentum jet while the associated particle comes from either the same jet or the away-side jet. Analysis of the angular width of the near-side peak in the correlation function determines the jet-fragmentation transverse momentum j(T). The extracted value, root < j(T)(2)>=585 +/- 6(stat)+/- 15(sys) MeV/c, is constant with respect to the trigger particle transverse momentum, and comparable to the previous lower root s measurements. The width of the away-side peak is shown to be a convolution of j(T) with the fragmentation variable, z, and the partonic transverse momentum, k(T). The < z > is determined through a combined analysis of the measured pi(0) inclusive and associated spectra using jet-fragmentation functions measured in e(+)e(-) collisions. The final extracted values of k(T) are then determined to also be independent of the trigger particle transverse momentum, over the range measured, with value of root < k(T)(2)>=2.68 +/- 0.07(stat)+/- 0.34(sys) GeV/c.
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| 40. |
- Adler, S. S., et al.
(författare)
-
Jet structure from dihadron correlations in d+Au collisions at root S-NN=200 GeV
- 2006
-
Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 73:5
-
Tidskriftsartikel (refereegranskat)abstract
- Dihadron correlations at high transverse momentum p(T) in d+Au collisions at root s(NN)=200 GeV at midrapidity are measured by the PHENIX experiment at the Relativistic Heavy Ion Collider. From these correlations, we extract several structural characteristics of jets: the root-mean-squared transverse momentum of fragmenting hadrons with respect to the jet root < j(T)(2)>, the mean sine-squared of the azimuthal angle between the jet axes < sin(2)phi(jj)>, and the number of particles produced within the dijet that are associated with a high-p(T) particle (dN/dx(E) distributions). We observe that the fragmentation characteristics of jets in d+Au collisions are very similar to those in p+p collisions and that there is little dependence on the centrality of the d+Au collision. This is consistent with the nuclear medium having little influence on the fragmentation process. Furthermore, there is no statistically significant increase in the value of < sin(2)phi(jj)> from p+p to d+Au collisions. This constrains the effect of multiple scattering that partons undergo in the cold nuclear medium before and after a hard collision.
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