A. A. Bickley
University of Colorado Boulder
Network
Latest external collaboration on country level. Dive into details by clicking on the dots.
Publication
Featured researches published by A. A. Bickley.
Nuclear Physics | 2005
B. B. Back; M. D. Baker; M. Ballintijn; D.S. Barton; Bruce Becker; Russell Richard Betts; A. A. Bickley; R. Bindel; A. Budzanowski; Wit Busza; A. Carroll; Z. Chai; M.P. Decowski; E. García; T. Gburek; N. George; K. Gulbrandsen; S. Gushue; C. Halliwell; J. Hamblen; A.S. Harrington; M. Hauer; G.A. Heintzelman; C. Henderson; David Jonathan Hofman; R. S. Hollis; R. Holynski; Burt Holzman; A. Iordanova; E. Johnson
This paper describes the conclusions that can be drawn from the data taken thus far with the PHOBOS detector at RHIC. In the most central Au+Au collisions at the highest beam energy, evidence is found for the formation of a very high energy density system whose description in terms of simple hadronic degrees of freedom is inappropriate. Furthermore, the constituents of this novel system are found to undergo a significant level of interaction. The properties of particle production at RHIC energies are shown to follow a number of simple scaling behaviors, some of which continue trends found at lower energies or in simpler systems. As a function of centrality, the total number of charged particles scales with the number of participating nucleons. When comparing Au+Au at different centralities, the dependence of the yield on the number of participants at higher p T (∼4 GeV/c) is very similar to that at low transverse momentum. The measured values of charged particle pseudorapidity density and elliptic flow were found to be independent of energy over a broad range of pseudorapidities when effectively viewed in the rest frame of one of the colliding nuclei, a property we describe as “extended longitudinal scaling”. Finally, the centrality and energy dependences of several observables were found to factorize to a surprising degree.
Physical Review Letters | 2007
A. Adare; S. Afanasiev; C. Aidala; N. N. Ajitanand; Y. Akiba; H. Al-Bataineh; J. Alexander; A. Al-Jamel; K. Aoki; L. Aphecetche; R. Armendariz; S. H. Aronson; J. Asai; E. T. Atomssa; R. Averbeck; T. C. Awes; B. Azmoun; V. Babintsev; G. Baksay; L. Baksay; A. Baldisseri; K. N. Barish; P. D. Barnes; B. Bassalleck; S. Bathe; S. Batsouli; V. Baublis; F. Bauer; A. Bazilevsky; S. Belikov
Differential measurements of elliptic flow (v2) for Au+Au and Cu+Cu collisions at sqrt[sNN]=200 GeV are used to test and validate predictions from perfect fluid hydrodynamics for scaling of v2 with eccentricity, system size, and transverse kinetic energy (KE T). For KE T identical with mT-m up to approximately 1 GeV the scaling is compatible with hydrodynamic expansion of a thermalized fluid. For large values of KE T mesons and baryons scale separately. Quark number scaling reveals a universal scaling of v2 for both mesons and baryons over the full KE T range for Au+Au. For Au+Au and Cu+Cu the scaling is more pronounced in terms of KE T, rather than transverse momentum.
Physical Review Letters | 2007
B. Alver; A. Iordanova; K. W. Wozniak; C. Halliwell; A. C. Mignerey; Constantin Loizides; Andrzej Olszewski; H. Seals; P. Steinberg; M. Hauer; F.L.H. Wolfs; S.S. Vaurynovich; C. Henderson; Willis Lin; B. Wyslouch; E. Garcia; P. Walters; I. Harnarine; Claude B. Reed; A. A. Bickley; S. Wyngaardt; G. van Nieuwenhuizen; Baker; B. Holzman; A. Szostak; G. S. F. Stephans; S. Manly; R. R. Betts; M. Ballintijn; M. B. Tonjes
This Letter presents measurements of the elliptic flow of charged particles as a function of pseudorapidity and centrality from Cu-Cu collisions at 62.4 and 200 GeV using the PHOBOS detector at the Relativistic Heavy Ion Collider. The elliptic flow in Cu-Cu collisions is found to be significant even for the most central events. For comparison with the Au-Au results, it is found that the detailed way in which the collision geometry (eccentricity) is estimated is of critical importance when scaling out system-size effects. A new form of eccentricity, called the participant eccentricity, is introduced which yields a scaled elliptic flow in the Cu-Cu system that has the same relative magnitude and qualitative features as that in the Au-Au system.
Physical Review C | 2011
B. Alver; B. B. Back; M. D. Baker; M. Ballintijn; D.S. Barton; R. R. Betts; A. A. Bickley; R. Bindel; A. Budzanowski; W. Busza; A. Carroll; Z. Chai; V. Chetluru; M.P. Decowski; E. García; T. Gburek; N. George; K. Gulbrandsen; S. Gushue; C. Halliwell; J. Hamblen; G.A. Heintzelman; C. Henderson; D. J. Hofman; R. S. Hollis; R. Holynski; B. Holzman; A. Iordanova; E. Johnson; J.L. Kane
Pseudorapidity distributions of charged particles emitted in Au+Au, Cu+Cu, d+Au, and p+p collisions over a wide energy range have been measured using the PHOBOS detector at the BNL Relativistic Heavy-Ion Collider (RHIC). The centrality dependence of both the charged particle distributions and the multiplicity at midrapidity were measured. Pseudorapidity distributions of charged particles emitted with |{eta}|<5.4, which account for between 95% and 99% of the total charged-particle emission associated with collision participants, are presented for different collision centralities. Both the midrapidity density dN{sub ch}/d{eta} and the total charged-particle multiplicity N{sub ch} are found to factorize into a product of independent functions of collision energy, {radical}(s{sub N{sub N}}), and centrality given in terms of the number of nucleons participating in the collision, N{sub part}. The total charged particle multiplicity, observed in these experiments and those at lower energies, assumes a linear dependence of (lns{sub N{sub N}}){sup 2} over the full range of collision energy of {radical}(s{sub N{sub N}})=2.7-200 GeV.
Physical Review Letters | 2006
A. Adare; S. Afanasiev; C. Aidala; N. N. Ajitanand; Y. Akiba; H. Al-Bataineh; J. Alexander; K. Aoki; L. Aphecetche; R. Armendariz; S. H. Aronson; J. Asai; E. T. Atomssa; R. Averbeck; T. C. Awes; B. Azmoun; V. Babintsev; G. Baksay; L. Baksay; A. Baldisseri; K. N. Barish; P. D. Barnes; B. Bassalleck; S. Bathe; S. Batsouli; V. Baublis; A. Bazilevsky; S. Belikov; R. Bennet; Y. Berdnikov
The momentum distribution of electrons from decays of heavy flavor (charm and bottom) for midrapidity absolute value of y < 0.35 in p + p collisions at square root of s = 200 GeV has been measured by the PHENIX experiment at the BNL Relativistic Heavy Ion Collider over the transverse momentum range 0.3 < pT < 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+/-0.02stat+/-0.18sys for 0.3 < pT < 9 GeV/c. The total charm production cross section at this energy has also been deduced to be sigma cc = 567+/-57stat+/-193sys microb.
Physical Review Letters | 2003
B. B. Back; A. Iordanova; A. Budzanowski; C. Halliwell; J. Zhang; A. Olszewski; P. Steinberg; F.L.H. Wolfs; W. Skulski; B. Wyslouch; K. W. Wozniak; C. Henderson; Willis Lin; E. Garcia; A.S. Harrington; C. Reed; A. A. Bickley; G. van Nieuwenhuizen; A. H. Wuosmaa; Baker; B. Holzman; C. Vale; R. Teng; I. C. Park; Bruce Becker; S. Manly; R. R. Betts; M. Ballintijn; M. B. Tonjes; D.S. Barton
We have measured transverse momentum distributions of charged hadrons produced in d+Au collisions at sqrt[s(NN)]=200 GeV. The spectra were obtained for transverse momenta 0.25<p(T)<6.0 GeV/c, in a pseudorapidity range of 0.2<eta<1.4 in the deuteron direction. The evolution of the spectra with collision centrality is presented in comparison to p+pmacr; collisions at the same collision energy. With increasing centrality, the yield at high transverse momenta increases more rapidly than the overall particle density, leading to a strong modification of the spectral shape. This change in spectral shape is qualitatively different from observations in Au+Au collisions at the same energy. The results provide important information for discriminating between different models for the suppression of high-p(T) hadrons observed in Au+Au collisions.
Physical Review C | 2011
A. Adare; S. Afanasiev; C. Aidala; N. N. Ajitanand; Y. Akiba; H. Al-Bataineh; J. Alexander; K. Aoki; Y. Aramaki; E. T. Atomssa; R. Averbeck; T. C. Awes; B. Azmoun; V. Babintsev; M. Bai; G. Baksay; L. Baksay; K. N. Barish; B. Bassalleck; A. T. Basye; S. Bathe; V. Baublis; C. Baumann; A. Bazilevsky; S. Belikov; R. Belmont; R. Bennett; A. Berdnikov; Y. Berdnikov; A. A. Bickley
Heavy quarkonia are observed to be suppressed in relativistic heavy-ion collisions relative to their production in p + p collisions scaled by the number of binary collisions. In order to determine if this suppression is related to color screening of these states in the produced medium, one needs to account for other nuclear modifications including those in cold nuclear matter. In this paper, we present new measurements from the PHENIX 2007 data set of J/psi yields at forward rapidity (1.2 < vertical bar y vertical bar < 2.2) in Au + Au collisions at root s(NN) = 200 GeV. The data confirm the earlier finding that the suppression of J/. at forward rapidity is stronger than at midrapidity, while also extending the measurement to finer bins in collision centrality and higher transverse momentum (p(T)). We compare the experimental data to the most recent theoretical calculations that incorporate a variety of physics mechanisms including gluon saturation, gluon shadowing, initial-state parton energy loss, cold nuclear matter breakup, color screening, and charm recombination. We find J/psi suppression beyond cold-nuclear-matter effects. However, the current level of disagreement between models and d + Au data precludes using these models to quantify the hot-nuclear-matter suppression.
Physical Review C | 2005
B. B. Back; W. Kucewicz; A. Iordanova; A. Budzanowski; C. Halliwell; Andrzej Olszewski; L. Rosenberg; P. Steinberg; M. Reuter; W. Skulski; J.-L. Tang; K. Wozniak; C. Henderson; Willis Lin; B. Wyslouch; E. García; C. Reed; A. A. Bickley; M. Nguyen; G. van Nieuwenhuizen; Baker; I.C. Park; G. S. F. Stephans; S. Manly; R.R. Betts; M. Ballintijn; R. Verdier; Marguerite Tonjes; G.A. Heintzelman; D.S. Barton
This paper describes the measurement of elliptic flow for charged particles in Au+Au collisions at sqrt(sNN)=200 GeV using the PHOBOS detector at the Relativistic Heavy Ion Collider (RHIC). The measured azimuthal anisotropy is presented over a wide range of pseudorapidity for three broad collision centrality classes for the first time at this energy. Two distinct methods of extracting the flow signal were used in order to reduce systematic uncertainties. The elliptic flow falls sharply with increasing eta at 200 GeV for all the centralities studied, as observed for minimum-bias collisions at sqrt(sNN)=130 GeV.
Physical Review Letters | 2004
B. B. Back; A. Iordanova; K. W. Wozniak; C. Halliwell; J. Zhang; A. Olszewski; P. Steinberg; F.L.H. Wolfs; W. Skulski; B. Wyslouch; C. Henderson; Willis Lin; E. Garcia; A.S. Harrington; C. Reed; A. A. Bickley; G. van Nieuwenhuizen; Baker; B. Holzman; C. Vale; I. C. Park; Bruce Becker; S. Manly; R. R. Betts; M. Ballintijn; M. B. Tonjes; D.S. Barton; P. Sarin; A. Carroll; W. Busza
The measured pseudorapidity distribution of primary charged particles in minimum-bias d+Au collisions at sqrt[s(NN)]=200 GeV is presented for the first time. This distribution falls off less rapidly in the gold direction as compared to the deuteron direction. The average value of the charged particle pseudorapidity density at midrapidity is |eta|< or =0.6)=9.4+/-0.7(syst) and the integrated primary charged particle multiplicity in the measured region is 82+/-6(syst). Estimates of the total charged particle production, based on extrapolations outside the measured pseudorapidity region, are also presented. The pseudorapidity distribution, normalized to the number of participants in d+Au collisions, is compared to those of Au+Au and p+(-)p systems at the same energy. The d+Au distribution is also compared to the predictions of the parton saturation model, as well as microscopic models.
Physical Review C | 2013
A. Adare; S. Afanasiev; C. Aidala; N. N. Ajitanand; Y. Akiba; H. Al-Bataineh; J. Alexander; K. Aoki; Y. Aramaki; E. T. Atomssa; R. Averbeck; T. C. Awes; B. Azmoun; V. Babintsev; M. Bai; G. Baksay; L. Baksay; K. N. Barish; B. Bassalleck; A. T. Basye; S. Bathe; V. Baublis; C. Baumann; A. Bazilevsky; S. Belikov; R. Belmont; R. Bennett; A. Berdnikov; Y. Berdnikov; A. A. Bickley
The PHENIX experiment has measured the production of pi(0)s in Au + Au collisions at root S-NN = 200 GeV. The new data offer a fourfold increase in recorded luminosity, providing higher precision and a larger reach in transverse momentum, p(T), to 20 GeV/c. The production ratio of eta/pi(0) is 0.46 +/- 0.01(stat) +/- 0.05(syst), constant with p(T) and collision centrality. The observed ratio is consistent with earlier measurements, as well as with the p + p and d + Au values. pi(0) are suppressed by a factor of 5, as in earlier findings. However, with the improved statistical precision a small but significant rise of the nuclear modification factor R-AA vs p(T), with a slope of 0.0106 +/-(0.0034)(0.0029) (Gev/c)(-1), is discernible in central collisions. A phenomenological extraction of the average fractional parton energy loss shows a decrease with increasing p(T). To study the path-length dependence of suppression, the pi(0) yield is measured at different angles with respect to the event plane; a strong azimuthal dependence of the pi(0) R-AA is observed. The data are compared to theoretical models of parton energy loss as a function of the path length L in the medium. Models based on perturbative quantum chromodynamics are insufficient to describe the data, while a hybrid model utilizing pQCD for the hard interactions and anti-de-Sitter space/conformal field theory (AdS/CFT) for the soft interactions is consistent with the data. DOI: 10.1103/PhysRevC.87.034911