Open Access. Powered by Scholars. Published by Universities.®

Physics Commons

Open Access. Powered by Scholars. Published by Universities.®

Iowa State University

2006

Discipline
Keyword
Publication
Publication Type

Articles 1 - 30 of 58

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.


Elastic Properties Of Gd5si2ge2 Studied With An Ultrasonic Pulse-Echo Technique, O. Svitelskiy, A. Suslov, Deborah L. Schlagel, Thomas A. Lograsso, Karl A. Gschneidner Jr., Vitalij K. Pecharsky Nov 2006

Elastic Properties Of Gd5si2ge2 Studied With An Ultrasonic Pulse-Echo Technique, O. Svitelskiy, A. Suslov, Deborah L. Schlagel, Thomas A. Lograsso, Karl A. Gschneidner Jr., Vitalij K. Pecharsky

Ames Laboratory Publications

We present the results of a study of the elastic properties of Gd5Si2Ge2, an alloy with giant magnetocaloric, magnetostrictive, and colossal magnetoresistive properties. Sound wave velocities measured in a number of different geometries allowed us to determine the whole elastic tensor for the monoclinic phase of this material. The anisotropy of the crystal is explored using the polar plots of the variations in the main crystallographic planes of the sound speed, the Young’s modulus, the shear modulus, and the linear compressibility. The effect of hydrostatic pressure on the Gd5Si2Ge2 ...


Posterminaries: After Nabarro, Alexander H. King Nov 2006

Posterminaries: After Nabarro, Alexander H. King

Alexander H. King

With the passing of Frank Nabarro in July of this year, we have lost one of the founding fathers of materials science. His name appears in many of the textbooks from which we train our students today, and also on the spines of several volumes on dislocation theory, including his classic monograph on the subject. He rightly stands among the gods of our field. Ninety years old at his death, he was a sprightly dancer at the frontiers of knowledge, right up to the end.


Numerical Simulations Of Gas-Liquid Flow Dynamics In Bubble Columns, Deify Law, Francine Battaglia, Theodore J. Heindel Nov 2006

Numerical Simulations Of Gas-Liquid Flow Dynamics In Bubble Columns, Deify Law, Francine Battaglia, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

There is great potential for using computational fluid dynamics (CFD) as a tool in scale-up and design of bubble columns. Full-scale experimentation in bubble columns is expensive and CFD is an alternative approach to study bubble column hydrodynamics. However, CFD can be computationally intensive as a predictive tool for a full three-dimensional geometry. In this paper, a 0.2 m diameter semi-batch bubble column is numerically simulated and the results are compared to experimental measurements performed by Rampure et al. [1]. The objectives are to examine and determine an appropriate set of numerical parameters and to determine if two-dimensional simulations ...


Phase Field Theory Of Surface- And Size-Induced Microstructures, Valery I. Levitas, D.W. Lee, D. L. Preston Oct 2006

Phase Field Theory Of Surface- And Size-Induced Microstructures, Valery I. Levitas, D.W. Lee, D. L. Preston

Valery I. Levitas

New surface- and size-induced microstructures are found as analytic solutions to a phase field theory of first-order phase transformations. A recently developed exact stability criterion, based on most destabilizing fluctuations, is used to analyze the stability and physical interpretation of each microstructure. Conditions for barrierless surface nucleation, i.e. relationship between surface energy, driving force for the transformation and sample size, are found. If they are met, some of these microstructures are destroyed resulting in the barrierless transformation to alternative phases.


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 ...


Sum Frequency Generation Vibrational Spectroscopic And High-Pressure Scanning Tunneling Microscopic Studies Of Benzene Hydrogenation On Pt(111), Kaitlin M. Bratlie, Max O. Montano, Lucio D. Flores, Matti Paajanen, Gabor A. Somorjai Oct 2006

Sum Frequency Generation Vibrational Spectroscopic And High-Pressure Scanning Tunneling Microscopic Studies Of Benzene Hydrogenation On Pt(111), Kaitlin M. Bratlie, Max O. Montano, Lucio D. Flores, Matti Paajanen, Gabor A. Somorjai

Kaitlin M. Bratlie

Sum frequency generation (SFG) vibrational spectroscopy and high-pressure scanning tunneling microscopy (HP-STM) have been used in combination for the first time to study a catalytic reaction. These techniques have been able to identify surface intermediates in situ during benzene hydrogenation on a Pt(111) single-crystal surface at Torr pressures.


Comment On “Structural Stability Of Complex Hydrides: Libh4 Revisited”, Duane D. Johnson, Nikolai A. Zarkevich Sep 2006

Comment On “Structural Stability Of Complex Hydrides: Libh4 Revisited”, Duane D. Johnson, Nikolai A. Zarkevich

Duane D. Johnson

A Comment on the Letter by Zbigniew Łodziana and Tejs Vegge, Phys. Rev. Lett. 93, 145501 (2004).


Short-Range Anisotropic Ferromagnetic Correlations In The Paramagnetic And Antiferromagnetic Phases Of Gd5ge4, Zhong W. Ouyang, Vitalij K. Pecharsky, Karl A. Gschneidner Jr., Deborah L. Schlagel, Thomas A. Lograsso Sep 2006

Short-Range Anisotropic Ferromagnetic Correlations In The Paramagnetic And Antiferromagnetic Phases Of Gd5ge4, Zhong W. Ouyang, Vitalij K. Pecharsky, Karl A. Gschneidner Jr., Deborah L. Schlagel, Thomas A. Lograsso

Ames Laboratory Publications

Signatures of short range anisotropic ferromagnetic correlations and ferromagnetic clustering, manifested as unusually large hysteresis and other anomalies of the low magnetic field dc magnetization and ac magnetic susceptibility, have been observed in both the antiferromagnetic and paramagnetic states of single crystal Gd5Ge4. Ferromagnetic correlations, which are most pronounced in a weak magnetic field applied along the b axis, are readily suppressed by fields exceeding ∼5 kOe and are believed to be related to a Griffiths-like phase that develops in Gd5Ge4 below TG≅240 K.


Posterminaries: The Scales Of Judgement, Alexander H. King Sep 2006

Posterminaries: The Scales Of Judgement, Alexander H. King

Alexander H. King

Materials scientists are generally well-versed in physics, and physics, above all, is a science of measurements. The first instinct of a physicist is to parse a problem in terms of its measurables in the dimensions of mass, length, and time, and it is the shifting of attention down the scale of length that particularly characterizes our present times as the Nano Age.


Magnetism Of (Dy0.5er0.5)Al2 Single Crystal In Ac And Dc Magnetic Fields, Evgenii M. Levin, Karl A. Gschneidner Jr., Thomas A. Lograsso, Deborah L. Schlagel Aug 2006

Magnetism Of (Dy0.5er0.5)Al2 Single Crystal In Ac And Dc Magnetic Fields, Evgenii M. Levin, Karl A. Gschneidner Jr., Thomas A. Lograsso, Deborah L. Schlagel

Ames Laboratory Publications

The temperature (4.2–90 K), ac magnetic field (1.25–50 Oe), frequency (5–125 Hz), and bias dc magnetic field (0–10 kOe) dependencies of the real and imaginary components of the ac magnetic susceptibility, and the temperature (4.2–250 K) and dc magnetic field(0.1–50 kOe) dependencies of the dc magnetic susceptibility and magnetization of a(Dy0.5Er0.5)Al2 single crystal have been studied. Isothermal magnetization measurement in a dc magnetic field indicates that (Dy0.5Er0.5)Al2 orders ferromagnetically at 37 K. The ac ...


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.


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 ...


Characterization Of Aperiodic And Periodic Thin Cu Films Formed On The Five-Fold Surface Of I-Al70pd21mn9 Using Medium-Energy Ion Scattering Spectroscopy, J. A. Smerdon, J. Ledieu, R. Mcgrath, T. C. Q. Noakes, P. Bailey, M. Draxler, C. F. Mcconville, Thomas A. Lograsso, A. R. Ross Jul 2006

Characterization Of Aperiodic And Periodic Thin Cu Films Formed On The Five-Fold Surface Of I-Al70pd21mn9 Using Medium-Energy Ion Scattering Spectroscopy, J. A. Smerdon, J. Ledieu, R. Mcgrath, T. C. Q. Noakes, P. Bailey, M. Draxler, C. F. Mcconville, Thomas A. Lograsso, A. R. Ross

Ames Laboratory Publications

The elucidation of the local atomic structure of a pseudomorphic film of Cu deposited on the five-fold surface of i-Al70Pd21Mn9using medium-energy ion scattering spectroscopy is reported. Monte Carlo calculations, using the VEGAS code, have been utilized to simulate the blocking of 100 keV He+ ions scattered from the overlayer. The coordinates of the Cu atoms in the overlayer derived from this procedure are consistent with a structure occurring in five rotational domains. Each domain consists of nanoscale strips of fcc Cu(100) with the ⟨110⟩ azimuth aligned along the five-fold directions of the quasicrystalline ...


Temperature And Magnetic-Field Dependence Of The Elastic Constants Of Ni-Mn-Al Magnetic Heusler Alloys, Xavier Moya, Lluís Mañosa, Antoni Planes, Thorsten Krenke, Mehmet Acet, Michel Morin, Jerel L. Zarestky, Thomas A. Lograsso Jul 2006

Temperature And Magnetic-Field Dependence Of The Elastic Constants Of Ni-Mn-Al Magnetic Heusler Alloys, Xavier Moya, Lluís Mañosa, Antoni Planes, Thorsten Krenke, Mehmet Acet, Michel Morin, Jerel L. Zarestky, Thomas A. Lograsso

Ames Laboratory Publications

We report on measurements of the adiabatic second-order elastic constants of the off-stoichiometric Ni54Mn23Al23 single-crystalline Heusler alloy. The variation in the temperature dependence of the elastic constants has been investigated across the magnetic transition and over a broad temperature range. Anomalies in the temperature behavior of the elastic constants have been found in the vicinity of the magnetic phase transition. Measurements under applied magnetic field, both isothermal and variable temperature, show that the value of the elastic constants depends on magnetic order, thus giving evidence for magnetoelastic coupling in this alloy system.


Magnetic Anisotropy And Magnetic Phase Diagram Of Gd5ge4, Zhong W. Ouyang, Vitalij K. Pecharsky, Karl A. Gschneidner Jr., Deborah L. Schlagel, Thomas A. Lograsso Jul 2006

Magnetic Anisotropy And Magnetic Phase Diagram Of Gd5ge4, Zhong W. Ouyang, Vitalij K. Pecharsky, Karl A. Gschneidner Jr., Deborah L. Schlagel, Thomas A. Lograsso

Ames Laboratory Publications

The magnetization of single crystal Gd5Ge4, which in a zero magnetic field orders antiferromagnetically at 128 K, indicates a reversible spin-flop transition when the magnetic field is along the c axis and the absence of similar transformations when the magnetic field vector is perpendicular to the c axis. This anisotropic behavior is due to variation of magnetization energy between the c axis and the a or b axes of the orthorhombic crystal caused by a different alignment of the Gd moments with respect to the magnetic field vector. The anisotropy of the antiferromagnetic state diminishes with the ...


Ginzburg-Landau Theory Of Microstructures: Stability, Transient Dynamics, And Functionally Graded Nanophases, Valery I. Levitas, D. L. Preston, Dong Wook Lee Jul 2006

Ginzburg-Landau Theory Of Microstructures: Stability, Transient Dynamics, And Functionally Graded Nanophases, Valery I. Levitas, D. L. Preston, Dong Wook Lee

Valery I. Levitas

The stability, transient dynamics, and physical interpretation of microstructures obtained from a Ginzburg-Landau theory of first-order phase transformations are studied. The Jacobi condition for stability fails numerically, thus an alternative exact stability criterion, based on critical (most destabilizing) fluctuations, is developed. The degree-of-stability parameter is introduced to quantify the physical stability of long-lived unstable microstructures. For nanofilms, the existence of functionally graded nanophases is demonstrated. Numerical simulations indicate that graded nanophases can be produced by dissolving material from both surfaces of a nanofilm. Stability under finite fluctuations and post-bifurcation microstructure evolution are investigated numerically.


Similitude Analysis For Gas-Liquid-Fiber Flows In Cocurrent Bubble Columns, Chengzhi Tang, Theodore J. Heindel Jul 2006

Similitude Analysis For Gas-Liquid-Fiber Flows In Cocurrent Bubble Columns, Chengzhi Tang, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Gas-liquid-fiber systems are different from conventional gas-liquid-solid systems in that the solid material (i.e., fiber) is flexible, has a large aspect ratio, and forms flocs or networks when its mass fraction is above a critical value. With its wide application to the pulp and paper industry, it is important to investigate the hydrodynamics of gas-liquid-fiber systems. In this paper, 19 parameters that influence gas holdup in gas-liquid-fiber bubble columns are critically examined and then a dimensional analysis based on the Buckingham Pi Theorem is used to derive the dimensionless parameters governing gas-liquid-fiber bubble column hydrodynamics. Seven dimensionless parameters that ...


The Effect Of A Modified Downcomer On The Hydrodynamics In An External Loop Airlift Reactor, Samuel T. Jones, Theodore J. Heindel Jul 2006

The Effect Of A Modified Downcomer On The Hydrodynamics In An External Loop Airlift Reactor, Samuel T. Jones, Theodore J. Heindel

Mechanical Engineering Conference Presentations, Papers, and Proceedings

Gas holdup and superficial liquid velocity in the downcomer and riser are studied for an external loop airlift reactor with an area ratio of 1:16. Two downcomer configurations are investigated consisting of the downcomer open or closed to the atmosphere. Experiments for these two configurations are carried out over a range of superficial gas velocities from UG = 0.5 to 20 cm/s using three aeration plates with open area ratios of 0.62, 0.99 and 2.22%. These results are compared to a bubble column operated with similar operating conditions. Experimental results show that the gas holdup ...


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 ...


Strongly Anisotropic Roughness In Surfaces Driven By An Oblique Particle Flux, Beate Schmittmann, Gunner Pruessner, Hans-Karl Janssen May 2006

Strongly Anisotropic Roughness In Surfaces Driven By An Oblique Particle Flux, Beate Schmittmann, Gunner Pruessner, Hans-Karl Janssen

Beate Schmittmann

Using field theoretic renormalization, an MBE-type growth process with an obliquely incident influx of atoms is examined. The projection of the beam on the substrate plane selects a “parallel” direction, with rotational invariance restricted to the transverse directions. Depending on the behavior of an effective anisotropic surface tension, a line of second-order transitions is identified, as well as a line of potentially first-order transitions, joined by a multicritical point. Near the second-order transitions and the multicritical point, the surface roughness is strongly anisotropic. Four different roughness exponents are introduced and computed, describing the surface in different directions, in real or ...


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 ...


Variation Of Magnetostriction With Temperature In Tb5si2.2ge1.8 Single Crystal, A. P. Ring, H. L. Ziegler, Thomas A. Lograsso, Deborah L. Schlagel, J. E. Snyder, David C. Jiles Apr 2006

Variation Of Magnetostriction With Temperature In Tb5si2.2ge1.8 Single Crystal, A. P. Ring, H. L. Ziegler, Thomas A. Lograsso, Deborah L. Schlagel, J. E. Snyder, David C. Jiles

Ames Laboratory Conference Papers, Posters, and Presentations

The Tb5(SixGe4−x) alloy system is similar to the better known Gd5(SixGe4−x), except it has a more complex magnetic and structural phase diagram. Gd5(SixGe1−x)4 has received much attention recently due to its giant magnetocaloric effect, colossal magnetostriction and giant magnetoresistance in the vicinity of a first order combined magnetic-structural phase transition. The magnetostriction changes that accompany the phase transitions of single crystal Tb5(Si2.2Ge1.8) have been investigated at temperatures between 20 and150 K by measurements of ...


Magnetostructural Transitions And Adiabatic Temperature Variation In Polycrystal And Single-Crystal Ni2mnga Alloys, C. P. Sasso, M. Pasquale, L. Giudici, S. Besseghini, E. Villa, L. H. Lewis, Thomas A. Lograsso, Deborah L. Schlagel Apr 2006

Magnetostructural Transitions And Adiabatic Temperature Variation In Polycrystal And Single-Crystal Ni2mnga Alloys, C. P. Sasso, M. Pasquale, L. Giudici, S. Besseghini, E. Villa, L. H. Lewis, Thomas A. Lograsso, Deborah L. Schlagel

Ames Laboratory Conference Papers, Posters, and Presentations

The magnetocaloric response of off-stoichiometric Ni2MnGa polycrystal and single-crystal samples with a Curie temperature coincident with the martensitic transition temperature was investigated. The direct measurement of temperature change (ΔTad) during an adiabatic transformation under a maximum field variation ΔH = 5.6×106 A/m (7 T) was performed. The polycrystalline sample shows a maximum ΔTad ≈ 1.5 K at a temperature close to the structural transition. The value of ΔTad and the 20 K span of the ΔTad peak encourage further studies of the effect of microstructure on ...


Spontaneous Generation Of Voltage In Single-Crystal Gd5si2ge2 During Magnetostructural Phase Transformations, Min Zou, H. Tang, Deborah L. Schlagel, Thomas A. Lograsso, Karl A. Gschneidner Jr., Vitalij K. Pecharsky Apr 2006

Spontaneous Generation Of Voltage In Single-Crystal Gd5si2ge2 During Magnetostructural Phase Transformations, Min Zou, H. Tang, Deborah L. Schlagel, Thomas A. Lograsso, Karl A. Gschneidner Jr., Vitalij K. Pecharsky

Ames Laboratory Conference Papers, Posters, and Presentations

The spontaneous generation of voltage (SGV) in single-crystal and polycrystallineGd5Si2Ge2 during the coupled magnetostructural transformation has been examined. Our experiments show reversible, measurable, and repeatable SGV responses of the materials to the temperature and magnetic field. The parameters of the response and the magnitude of the signal are anisotropic and rate dependent. The magnitude of the SGV signal and the critical temperatures and critical magnetic fields at which the SGV occurs vary with the rate of temperature and magnetic-field changes.


Lattice And Spin Dynamics In Bcc Fe, 10 At. % Be, P. Zhao, J. Cullen, M. Wuttig, H. J. Kang, J. W. Lynn, Thomas A. Lograsso, O. Moze Apr 2006

Lattice And Spin Dynamics In Bcc Fe, 10 At. % Be, P. Zhao, J. Cullen, M. Wuttig, H. J. Kang, J. W. Lynn, Thomas A. Lograsso, O. Moze

Ames Laboratory Conference Papers, Posters, and Presentations

Body centered cubic Fe1−xBex alloys are known to display an enhanced tetragonal magnetostriction compared to Fe. In order to characterize the enhanced magnetoelasticity observed in this alloy system, we present detailed inelastic neutron scattering measurements of the phonon dispersion relations of a single crystal of bcc Fe, 10 at. %Be along the high symmetry directions [100], [110], and [111] at room temperature. We observe in particular that the frequency of transverse phonons propagating along the [110] direction with a [10] polarization at the zone boundary is reduced by 10% with respect to bcc Fe (the corresponding ...


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 ...