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Full-Text Articles in Physics

Measurement Of High-P(T) Single Electrons From Heavy-Flavor Decays In P+P Collisions At Root S=200 Gev, Andrew Adare, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, H. Pei, Marzia Rosati, S. Skutnik, Carla Vale, Et Al., Phenix Collaboration Dec 2006

Measurement Of High-P(T) Single Electrons From Heavy-Flavor Decays In P+P Collisions At Root S=200 Gev, Andrew Adare, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, H. Pei, Marzia Rosati, S. Skutnik, Carla Vale, Et Al., Phenix Collaboration

Physics and Astronomy Publications

The momentum distribution of electrons from decays of heavy flavor (charm and bottom) for midrapidity |y|< 0.35 in p+p collisions at s=200 GeV has been measured by the PHENIX experiment at the BNL Relativistic Heavy Ion Collider over the transverse momentum range 0.3 < p(T)< 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 +/- 0.02(stat)+/- 0.18(sys) for 0.3 < p(T)< 9 GeV/c. The total charm production cross section at this energy has also been deduced to be sigma(cc)=567 +/- 57(stat)+/- 193(sys) mu b.


Jet Properties From Dihadron Correlations In P Plus P Collisions At Root S=200 Gev, S. S. Adler, Sergey Belikov, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, H Pei, Jan Rak, Marzia Rosati, F. K. Wohn, X. Zong, Et Al., Phenix Collaboration Oct 2006

Jet Properties From Dihadron Correlations In P Plus P Collisions At Root S=200 Gev, S. S. Adler, Sergey Belikov, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, H Pei, Jan Rak, Marzia Rosati, F. K. Wohn, X. Zong, Et Al., Phenix Collaboration

Physics and Astronomy Publications

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 ...


Chemical Diffusion Of Co In Mixed Co+O Adlayers And Reaction-Front Propagation In Co Oxidation On Pd(100), Da-Jiang Liu, James W. Evans Aug 2006

Chemical Diffusion Of Co In Mixed Co+O Adlayers And Reaction-Front Propagation In Co Oxidation On Pd(100), Da-Jiang Liu, James W. Evans

Physics and Astronomy Publications

Within the framework of a realistic atomistic lattice-gas model, we present the theoretical formulation and simulation procedures for precise analysis of the chemical diffusion flux of highly mobile CO within a nonuniform interacting mixed CO+O adlayer on a Pd(100) surface. The approach applies in both regimes of relatively immobile unequilibrated and fairly mobile near-equilibrated O adlayer distributions. Spatiotemporal behavior in surface reactions is controlled by chemical diffusion in mixed adlayers. Thus, we naturally integrate the above analysis with a previously developed multiscale modeling strategy to describe mesoscale reaction front propagation in CO oxidation on Pd(100). This treatment ...


Nuclear Effects On Hadron Production In D Plus Au Collisions At Root S-Nn=200 Gev Revealed By Comparison With P Plus P Data, S. S. Adler, Sergey Belikov, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, H. Pei, Jan Rak, Marzia Rosati, F. K. Wohn, X. Zong, Et Al., Phenix Collaboration Aug 2006

Nuclear Effects On Hadron Production In D Plus Au Collisions At Root S-Nn=200 Gev Revealed By Comparison With P Plus P Data, S. S. Adler, Sergey Belikov, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, H. Pei, Jan Rak, Marzia Rosati, F. K. Wohn, X. Zong, Et Al., Phenix Collaboration

Physics and Astronomy Publications

PHENIX has measured the centrality dependence of midrapidity pion, kaon, and proton transverse momentum distributions in d+Au and p+p collisions at root s(NN) = 200 GeV. The p+p data provide a reference for nuclear effects in d+Au and previously measured Au+Au collisions. Hadron production is enhanced in d+Au, relative to independent nucleon-nucleon scattering, as was observed in lower energy collisions. The nuclear modification factor for (anti)protons is larger than that for pions. The difference increases with centrality but is not sufficient to account for the abundance of baryon production observed in central Au ...


Dense-Medium Modifications To Jet-Induced Hadron Pair Distributions In Au+Au Collisions At Root(Nn)-N-S=200 Gev, S. S. Adler, Sergey Belikov, S. Bhagavatula, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Jan Rak, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration Aug 2006

Dense-Medium Modifications To Jet-Induced Hadron Pair Distributions In Au+Au Collisions At Root(Nn)-N-S=200 Gev, S. S. Adler, Sergey Belikov, S. Bhagavatula, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Jan Rak, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration

Physics and Astronomy Publications

Azimuthal correlations of jet-induced high-p(T) charged hadron pairs are studied at midrapidity in Au+Au collisions at root s(NN)=200 GeV. The distribution of jet-associated partner hadrons (1.0 < p(T)< 2.5 GeV/c) per trigger hadron (2.5 < p(T)< 4.0 GeV/c) is found to vary with collision centrality, in both shape and yield, indicating a significant effect of the nuclear collision medium on the jet fragmentation process.


Azimuthal Angle Correlations For Rapidity Separated Hadron Pairs In D+Au Collisions At Root S(Nn)=200 Gev, S. S. Adler, Sergey Belikov, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, H. Pei, Jan Rak, Marzia Rosati, F. K. Wohn, X. Zong, Et Al., Phenix Collaboration Jun 2006

Azimuthal Angle Correlations For Rapidity Separated Hadron Pairs In D+Au Collisions At Root S(Nn)=200 Gev, S. S. Adler, Sergey Belikov, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, H. Pei, Jan Rak, Marzia Rosati, F. K. Wohn, X. Zong, Et Al., Phenix Collaboration

Physics and Astronomy Publications

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 ...


Jet Structure From Dihadron Correlations In D+Au Collisions At Root S-Nn=200 Gev, S. S. Adler, Sergey Belikov, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, H. Pei, Jan Rak, Marzia Rosati, F. K. Wohn, X. Zong, Et Al., Phenix Collaboration May 2006

Jet Structure From Dihadron Correlations In D+Au Collisions At Root S-Nn=200 Gev, S. S. Adler, Sergey Belikov, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, H. Pei, Jan Rak, Marzia Rosati, F. K. Wohn, X. Zong, Et Al., Phenix Collaboration

Physics and Astronomy Publications

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 ...


Common Suppression Pattern Of Eta And Pi(0) Mesons At High Transverse Momentum In Au Plus Au Collisions At Root Snn=200 Gev, S. S. Adler, Sergey Belikov, S. Bhagavatula, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Jan Rak, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration May 2006

Common Suppression Pattern Of Eta And Pi(0) Mesons At High Transverse Momentum In Au Plus Au Collisions At Root Snn=200 Gev, S. S. Adler, Sergey Belikov, S. Bhagavatula, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Jan Rak, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration

Physics and Astronomy Publications

Inclusive transverse momentum spectra of eta mesons have been measured within p(T)=2-10 GeV/c at midrapidity by the PHENIX experiment in Au+Au collisions at root s(NN) = 200 GeV. In central Au+Au the eta yields are significantly suppressed compared to peripheral Au+Au, d+Au, and p+p yields scaled by the corresponding number of nucleon-nucleon collisions. The magnitude, centrality, and p(T) dependence of the suppression is common, within errors, for eta and pi(0). The ratio of eta to pi(0) spectra at high p(T) amounts to 0.40 < R-eta/pi(0)< 0.48 for the three systems, in agreement with the world average measured in hadronic and nuclear reactions and, at large scaled momentum, in e(+)e(-) collisions.


Improved Measurement Of Double Helicity Asymmetry In Inclusive Midrapidity Pi(0) Production For Polarized P+P Collisions At Root S=200 Gev, S. S. Adler, Sergey Belikov, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, H. Pei, Jan Rak, Marzia Rosati, S. Skutnik, F. K. Wohn, X. Zong, Et Al., Phenix Collaboration May 2006

Improved Measurement Of Double Helicity Asymmetry In Inclusive Midrapidity Pi(0) Production For Polarized P+P Collisions At Root S=200 Gev, S. S. Adler, Sergey Belikov, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, H. Pei, Jan Rak, Marzia Rosati, S. Skutnik, F. K. Wohn, X. Zong, Et Al., Phenix Collaboration

Physics and Astronomy Publications

We present an improved measurement of the double helicity asymmetry for pi(0) production in polarized proton-proton scattering at root s=200 GeV employing the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The improvements to our previous measurement come from two main factors: Inclusion of a new data set from the 2004 RHIC run with higher beam polarizations than the earlier run and a recalibration of the beam polarization measurements for the earlier run, which resulted in reduced uncertainties and increased beam polarizations. The results are compared to a Next to Leading Order (NLO) perturbative Quantum Chromodynamics (pQCD ...


Atomistic Lattice-Gas Modeling Of Co Oxidation On Pd(100): Temperature-Programed Spectroscopy And Steady-State Behavior, Da-Jiang Liu, James W. Evans Apr 2006

Atomistic Lattice-Gas Modeling Of Co Oxidation On Pd(100): Temperature-Programed Spectroscopy And Steady-State Behavior, Da-Jiang Liu, James W. Evans

Physics and Astronomy Publications

We have developed an atomistic lattice-gas model for the catalytic oxidation of CO on single-crystal Pd(100) surfaces under ultrahigh vacuum conditions. This model necessarily incorporates an detailed description of adlayer ordering and adsorption-desorption kinetics both for CO on Pd(100), and for oxygen on Pd(100). Relevant energetic parameters are determined by comparing model predictions with experiment, together with some guidance from density functional theory calculations. The latter also facilitates description of the interaction and reaction of adsorbed CO and oxygen. Kinetic Monte Carlo simulations of this reaction model are performed to predict temperature- programed reaction spectra, as well ...


Mound Slope And Shape Selection During Unstable Multilayer Growth: Analysis Of Step-Dynamics Models Including Downward Funneling, Maozhi Li, James W. Evans Mar 2006

Mound Slope And Shape Selection During Unstable Multilayer Growth: Analysis Of Step-Dynamics Models Including Downward Funneling, Maozhi Li, James W. Evans

Physics and Astronomy Publications

Step-dynamics models are developed for mound shape evolution during multilayer homoepitaxial growth in the presence of inhibited interlayer transport. Unconventionally, our models also incorporate downward funneling (DF) of atoms deposited at step edges. The extent of DF can be reduced continuously to zero where one recovers traditional step dynamics models. This allows direct comparison between the behavior of models with and without DF. We show that DF greatly enhances growth of the height of valleys at the mound bases to an extent compatible with slope selection. To elucidate the selected shapes of finite mounds, we consider a suitably defined net ...


Nuclear Modification Of Electron Spectra And Implications For Heavy Quark Energy Loss In Au + Au Collisions At Root S(Nn)=200 Gev, S. S. Adler, Sergey Belikov, S. Bhagavatula, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Jan Rak, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration Jan 2006

Nuclear Modification Of Electron Spectra And Implications For Heavy Quark Energy Loss In Au + Au Collisions At Root S(Nn)=200 Gev, S. S. Adler, Sergey Belikov, S. Bhagavatula, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Jan Rak, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration

Physics and Astronomy Publications

The PHENIX experiment has measured midrapidity (vertical bar eta vertical bar < 0.35) transverse momentum spectra (0.4 < p(T)< 5.0 GeV/c) of electrons as a function of centrality in Au+Au collisions at root s(NN) = 200 GeV. Contributions from photon conversions and from light hadron decays, mainly Dalitz decays of pi(0) and eta mesons, were removed. The resulting nonphotonic electron spectra are primarily due to the semileptonic decays of hadrons carrying heavy quarks. Nuclear modification factors were determined by comparison to nonphotonic electrons in p+p collisions. A significant suppression of electrons at high p(T) is observed in central Au+Au collisions, indicating substantial energy loss of heavy quarks.


Measurement Of Identified Pi(0) And Inclusive Photon Second-Harmonic Parameter V(2) And Implications For Direct Photon Production In Root S(Nn)=200 Gev, S. S. Adler, Sergey Belikov, S. Bhagavatula, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Jan Rak, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration Jan 2006

Measurement Of Identified Pi(0) And Inclusive Photon Second-Harmonic Parameter V(2) And Implications For Direct Photon Production In Root S(Nn)=200 Gev, S. S. Adler, Sergey Belikov, S. Bhagavatula, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Jan Rak, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration

Physics and Astronomy Publications

The azimuthal distribution of identified pi(0) and inclusive photons has been measured in root s(NN)=200 GeV Au+Au collisions with the PHENIX experiment at the Relativistic Heavy-Ion Collider (RHIC). The second-harmonic parameter (v(2)) was measured to describe the observed anisotropy of the azimuthal distribution. The measured inclusive photon v(2) is consistent with the value expected for the photons from hadron decay and is also consistent with the lack of direct photon signal over the measured p(T) range 1-6 GeV/c. An attempt is made to extract v(2) of direct photons.


Single Electrons From Heavy-Flavor Decays In P + P Collisions At Root S=200 Gev, S. S. Adler, Sergey Belikov, S. Bhagavatula, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Jan Rak, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration Jan 2006

Single Electrons From Heavy-Flavor Decays In P + P Collisions At Root S=200 Gev, S. S. Adler, Sergey Belikov, S. Bhagavatula, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, Jan Rak, Marzia Rosati, F. K. Wohn, Et Al., Phenix Collaboration

Physics and Astronomy Publications

The invariant differential cross section for inclusive electron production in p+p collisions at root s=200 GeV has been measured by the PHENIX experiment at the BNL Relativistic Heavy Ion Collider over the transverse momentum range 0.4 <= p(T) <= 5.0 GeV/c in the central rapidity region (vertical bar eta vertical bar <= 0.35). The contribution to the inclusive electron spectrum from semileptonic decays of hadrons carrying heavy flavor, i.e., charm quarks or, at high p(T), bottom quarks, is determined via three independent methods. The resulting electron spectrum from heavy-flavor decays is compared to recent leading and next-to-leading order perturbative QCD calculations. The total cross section of charm quark-antiquark pair production is determined to be sigma(c (c) over bar) = 0.92 +/- 0.15(stat) +/- 0.54(syst) mb.


J/Psi Production And Nuclear Effects For D+Au And P+P Collisions At Root S-Nn=200 Gev, S. S. Adler, Sergey Belikov, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, H. Pei, Jan Rak, Marzia Rosati, F. K. Wohn, X. Zong, Et Al., Phenix Collaboration Jan 2006

J/Psi Production And Nuclear Effects For D+Au And P+P Collisions At Root S-Nn=200 Gev, S. S. Adler, Sergey Belikov, Paul Constantin, Nathan C. Grau, John C. Hill, John G. Lajoie, Alexandre Lebedev, Craig Ogilvie, H. Pei, Jan Rak, Marzia Rosati, F. K. Wohn, X. Zong, Et Al., Phenix Collaboration

Physics and Astronomy Publications

J/psi production in d+Au and p+p collisions at root s(NN)=200 GeV has been measured by the PHENIX experiment at rapidities -2.2 < y <+2.4. The cross sections and nuclear dependence of J/psi production versus rapidity, transverse momentum, and centrality are obtained and compared to lower energy p+A results and to theoretical models. The observed nuclear dependence in d+Au collisions is found to be modest, suggesting that the absorption in the final state is weak and the shadowing of the gluon distributions is small and consistent with Dokshitzer-Gribov-Lipatov-Altarelli-Parisi-based parametrizations that fit deep-inelastic scattering and Drell-Yan data at lower energies.


Cloning, Expression, Purification, Crystallization And Preliminary X-Ray Diffraction Analysis Of The Regulator Acrr From Escherichia Coli, Ming Li, Xi Qiu, Chih-Chia Su, Feng Long, Ruoyu Gu, Gerry Mcdermott, Edward Yu Jan 2006

Cloning, Expression, Purification, Crystallization And Preliminary X-Ray Diffraction Analysis Of The Regulator Acrr From Escherichia Coli, Ming Li, Xi Qiu, Chih-Chia Su, Feng Long, Ruoyu Gu, Gerry Mcdermott, Edward Yu

Physics and Astronomy Publications

This paper describes the cloning, expression, purification and preliminary X-ray data analysis of the AcrR regulatory protein. The Escherichia coli AcrR is a member of the TetR family of transcriptional regulators. It regulates the expression of the AcrAB multidrug transporter. Recombinant AcrR with a 6×His tag at the C-terminus was expressed in E. coli and purified by metal-affinity chromatography. The protein was crystallized using hanging-drop vapor diffusion. X-ray diffraction data were collected from cryocooled crystals at a synchrotron light source. The best crystal diffracted to 2.5 Å. The space group was determined to be P32, with ...


Conformation Of The Acrb Multidrug Efflux Pump In Mutants Of The Putative Proton Relay Pathway, Chih-Chia Su, Ming Li, Ruoyu Gu, Yumiko Takatsuka, Gerry Mcdermott, Hiroshi Nikaido, Edward Yu Jan 2006

Conformation Of The Acrb Multidrug Efflux Pump In Mutants Of The Putative Proton Relay Pathway, Chih-Chia Su, Ming Li, Ruoyu Gu, Yumiko Takatsuka, Gerry Mcdermott, Hiroshi Nikaido, Edward Yu

Physics and Astronomy Publications

We previously reported the X-ray structures of wild-type Escherichia coli AcrB, a proton motive force-dependent multidrug efflux pump, and its N109A mutant. These structures presumably reflect the resting state of AcrB, which can bind drugs. After ligand binding, a proton may bind to an acidic residue(s) in the transmembrane domain, i.e., Asp407 or Asp408, within the putative network of electrostatically interacting residues, which also include Lys940 and Thr978, and this may initiate a series of conformational changes that result in drug expulsion. Herein we report the X-ray structures of four AcrB mutants, the D407A, D408A, K940A, and T978A ...


Production Of Q Anti-Q Pairs In Proton-Nucleus Collisions At High Energies, Yuri V. Kovchegov, Kirill Tuchin Jan 2006

Production Of Q Anti-Q Pairs In Proton-Nucleus Collisions At High Energies, Yuri V. Kovchegov, Kirill Tuchin

Physics and Astronomy Publications

We calculate production of quark-antiquark pairs in high energy proton-nucleus collisions both in the quasiclassical approximation of McLerran-Venugopalan model and including quantum small-x evolution. The resulting production cross section is explicitly expressed in terms of Glauber-Mueller multiple rescatterings in the classical case and in terms of dipole-nucleus scattering amplitude in the quantum evolution case. We generalize the result of beyond the aligned jet configurations. We expand on the earlier results of Blaizot, Gelis and Venugopalan by deriving quark production cross section including quantum evolution corrections in rapidity intervals both between the quarks and the target and between the quarks and ...