| 1. |
- Adler, SS, et al.
(författare)
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Bose-Einstein correlations of charged pion pairs in Au+Au collisions at root(NN)-N-s = 200 GeV
- 2004
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Ingår i: Physical Review Letters. - 1079-7114. ; 93:15
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Tidskriftsartikel (refereegranskat)abstract
- Bose-Einstein correlations of identically charged pion pairs were measured by the PHENIX experiment at midrapidity in Au+Au collisions at roots(NN)=200 GeV. The Bertsch-Pratt radius parameters were determined as a function of the transverse momentum of the pair and as a function of the centrality of the collision. Using the standard core-halo partial Coulomb fits, and a new parametrization which constrains the Coulomb fraction as determined from the unlike-sign pion correlation, the ratio R-out/R-side is within 0.8-1.1 for 0.25<<1.2 GeV/c. The centrality dependence of all radii is well described by a linear scaling in N-part(1/3), and R-out/R-side for similar to0.45 GeV/c is approximately constant at unity as a function of centrality.
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| 2. |
- Adler, SS, et al.
(författare)
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Elliptic flow of identified hadrons in Au+Au collisions at root s(NN)=200 GeV
- 2003
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Ingår i: Physical Review Letters. - 1079-7114. ; 91:18: 182301
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Tidskriftsartikel (refereegranskat)abstract
- The anisotropy parameter (v(2)), the second harmonic of the azimuthal particle distribution, has been measured with the PHENIX detector in Au+Au collisions at roots(NN)=200 GeV for identified and inclusive charged particle production at central rapidities (eta<0.35) with respect to the reaction plane defined at high rapidities (eta=3-4 ). We observe that the v(2) of mesons falls below that of (anti)baryons for p(T)>2 GeV/c, in marked contrast to the predictions of a hydrodynamical model. A quark-coalescence model is also investigated.
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| 3. |
- Adler, SS, et al.
(författare)
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J/psi production from proton-proton collisions at root s=200 GeV
- 2004
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Ingår i: Physical Review Letters. - 1079-7114. ; 92:5
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Tidskriftsartikel (refereegranskat)abstract
- J/psi production has been measured in proton-proton collisions at roots=200 GeV over a wide rapidity and transverse momentum range by the PHENIX experiment at the Relativistic Heavy Ion Collider. Distributions of the rapidity and transverse momentum, along with measurements of the mean transverse momentum and total production cross section are presented and compared to available theoretical calculations. The total J/psi cross section is 4.0+/-0.6(stat)+/-0.6(syst)+/-0.4(abs) mub. The mean transverse momentum is 1.80+/-0.23(stat)+/-0.16(syst) GeV/c.
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| 4. |
- Adler, SS, et al.
(författare)
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J/psi production in Au-Au collisions at root s(NN)=200 GeV
- 2004
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 69:1
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Tidskriftsartikel (refereegranskat)abstract
- First results on charm quarkonia production in heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) are presented. The yield of J/psi's measured in the PHENIX experiment via electron-positron decay pairs at midrapidity for Au-Au reactions at roots(NN) = 200 GeV is analyzed as a function of collision centrality. For this analysis we have studied 49.3x10(6) minimum bias Au-Au reactions. We present the J/psi invariant yield dN/dy for peripheral and midcentral reactions. For the most central collisions where we observe no signal above background, we quote 90% confidence level upper limits. We compare these results with our J/psi measurement from proton-proton reactions at the same energy. We find that our measurements are not consistent with models that predict strong enhancement relative to binary collision scaling.
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| 5. |
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| 6. |
- Adler, SS, et al.
(författare)
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Scaling properties of proton and antiproton production in root s(NN)=200 GeV Au+Au collisions
- 2003
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Ingår i: Physical Review Letters. - 1079-7114. ; 91:17: 172301
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Tidskriftsartikel (refereegranskat)abstract
- We report on the yield of protons and antiprotons, as a function of centrality and transverse momentum, in Au+Au collisions at rootS(NN)=200 GeV measured at midrapidity by the PHENIX experiment at the BNL Relativistic Heavy Ion Collider. In central collisions at intermediate transverse momenta (1.5
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| 7. |
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| 8. |
- Adler, SS, et al.
(författare)
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Double helicity asymmetry in inclusive midrapidity pi(0) production for polarized p+p collisions at root s=200 GeV
- 2004
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Ingår i: Physical Review Letters. - 1079-7114. ; 93:20: 202002
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Tidskriftsartikel (refereegranskat)abstract
- We present a measurement of the double longitudinal spin asymmetry in inclusive pi(0) production in polarized proton-proton collisions at roots=200 GeV. The data were taken at the Relativistic Heavy Ion Collider with average beam polarizations of 0.27. The measurements are the first in a program to study the longitudinal spin structure of the proton, using strongly interacting probes, at collider energies. The asymmetry is presented for transverse momenta 1-5 GeV/c at midrapidity, where next-to-leading-order perturbative quantum chromodynamic (NLO pQCD) calculations well describe the unpolarized cross section. The observed asymmetry is small and is compared to a NLO pQCD calculation with a range of polarized gluon distributions.
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| 9. |
- Alcorn, J, et al.
(författare)
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Basic instrumentation for Hall A at Jefferson Lab
- 2004
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - : Elsevier BV. - 0167-5087 .- 0168-9002. ; 522:3, s. 294-346
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Tidskriftsartikel (refereegranskat)abstract
- The instrumentation in Hall A at the Thomas Jefferson National Accelerator Facility was designed to study electro-and photo-induced reactions at very high luminosity and good momentum and angular resolution for at least one of the reaction products. The central components of Hall A are two identical high resolution spectrometers, which allow the vertical drift chambers in the focal plane to provide a momentum resolution of better than 2 x 10(-4). A variety of Cherenkov counters, scintillators and lead-glass calorimeters provide excellent particle identification. The facility has been operated successfully at a luminosity well in excess of 10(38) CM-2 s(-1). The research program is aimed at a variety of subjects, including nucleon structure functions, nucleon form factors and properties of the nuclear medium. (C) 2003 Elsevier B.V. All rights reserved.
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| 10. |
- Choi, Y S, et al.
(författare)
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Fast antenna selection algorithms for MIMO systems
- 2003
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Ingår i: IEEE 58th Vehicular Technology Conference, 2003. VTC 2003-Fall.. - 1090-3038. - 0780379543 ; 3, s. 1733-1737
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Konferensbidrag (refereegranskat)abstract
- We consider the capacity of multiple-input-multiple-output (MIMO) systems with reduced complexity. One link end uses all available antennas, while the other chooses the "best" L out of N antennas. The selection of the optimum antenna subset requires an exhaustive search of all possible combinations, involving (/sub L//sup N/) computations of determinants of size L /spl times/ L, which can become prohibitively complex. In this paper, we suggest a class of fast antenna selection algorithm that are based on the correlation or mutual information between the signals at the different antenna elements. It requires less than N/sup 2/ vector multiplications and thus leads to dramatic savings on the computation time. Its performance is very close to the optimum selection procedure: the capacity penalty is less than l bit/s/Hz for the analyzed examples. The algorithm thus offers the possibility of almost-optimum selection even in fast-changing environments.
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| 11. |
- Kim, Beom Jun, et al.
(författare)
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Dynamic instabilities induced by asymmetric influence : Prisoners' dilemma game in small-world networks
- 2002
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Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - 1063-651X .- 1095-3787. ; 66:2, s. 021907-
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Tidskriftsartikel (refereegranskat)abstract
- A two-dimensional small-world-type network, subject to spatial prisoners' dilemma dynamics and containing an influential node defined as a special node, with a finite density of directed random links to the other nodes in the network, is numerically investigated. It is shown that the degree of cooperation does not remain at a steady state level but displays a punctuated equilibrium-type behavior manifested by the existence of sudden breakdowns of cooperation. The breakdown of cooperation is linked to an imitation of a successful selfish strategy of the influential node. It is also found that while the breakdown of cooperation occurs suddenly, its recovery requires longer time. This recovery time may, depending on the degree of steady state cooperation, either increase or decrease with an increasing number of long-range connections.
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| 12. |
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| 13. |
- Kim, Beom Jun, et al.
(författare)
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XY model in small-world networks
- 2001
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Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - 1063-651X .- 1095-3787. ; 64:5, s. 056135-
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Tidskriftsartikel (refereegranskat)abstract
- The phase transition in the XY model on one-dimensional small-world networks is investigated by means of Monte Carlo simulations. It is found that long-range order is present at finite temperatures, even for very small values of the rewiring probability, suggesting a finite-temperature transition for any nonzero rewiring probability. Nature of the phase transition is discussed in comparison with the globally coupled XY model.
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| 14. |
- Kim, Beom Jun, et al.
(författare)
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XY model in small-world networks
- 2001
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Ingår i: Physical Review E. - 1063-651X. ; 64:5, s. 056135-
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Tidskriftsartikel (refereegranskat)
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| 15. |
- Lee, S., et al.
(författare)
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Effect of be doping on the properties of GaMnAs ferromagnetic semiconductors
- 2003
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 93:10 3, s. 8307-8309
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Tidskriftsartikel (refereegranskat)abstract
- The effect of Be doping on the properties of GaMnAs ferromagnetic semiconductors was analyzed. The samples were characterized using SQUID and magnetotransport measurements. The observed increase in the critical temperature in Ga 1-xMn xAs for the low range of x can be explained by the increase of free carrier concentrations in the system arising from Be doping.
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| 16. |
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| 17. |
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| 18. |
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| 19. |
- Seong, K, et al.
(författare)
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A new adaptive transmission scheme for wireless communication systems utilizing frequency diversity
- 2002
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Ingår i: Wireless personal communications. - 0929-6212 .- 1572-834X. ; 23:1, s. 45-53
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we propose a new adaptive transmission scheme for wireless communication systems utilizing frequency diversity combining technique. The capacity of Rayleigh fading chanels under the proposed adaptive transmission scheme is analytically evaluated and compared with the capacity under the conventional adaptive transmission scheme. The results show that the channel capacity under the new adaptive scheme exceeds that under the conventional one, and this capacity increment becomes more apparent especially for lower average carrier-to-noise ratio (CNR) and larger number of diversity branches. Also, the capacity with the new scheme isshown to exceed even the capacity of AWGN channels for some small values of CNR and large number of diversity branches.
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| 20. |
- Youn, Byeng Dong, et al.
(författare)
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Techniques for estimating uncertainty propagation in probabilistic design of multilevel systems
- 2004
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Ingår i: A collection of technical papers. - Reston, Va. : American Institute of Aeronautics and Astronautics, AIAA. - 1563477165 ; , s. 1893-1902
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Konferensbidrag (refereegranskat)abstract
- In probabilistic design of multilevel systems, the challenge is to estimate uncertainty propagation since outputs of subsystems at lower levels constitute inputs of subsystems at higher levels. Three uncertainty propagation estimation techniques are compared in this paper in terms of numerical efficiency and accuracy: root sum square (linearization), distribution-based moment approximation, and Taguchi-based integration. When applied to simulation-based, multilevel system design optimization under uncertainty, it is investigated which type of applications each method is best suitable for. The probabilistic formulation of the analytical target cascading methodology is used to solve the multilevel problem. A hierarchical bi-level engine design problem is employed to investigate unique features of the presented techniques for uncertainty propagation. This study aims at helping potential users to identify appropriate techniques for their applications. Copyright © 2004 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.
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