Flow In Cu Research Articles

Autowave Process of Plastic Flow in Cu–Ni Alloys

Autowave Process of Plastic Flow in Cu–Ni Alloys

Azimuthal anisotropy in Cu+Au collisions at sNN=200 GeV

The azimuthal anisotropic flow of identified and unidentified charged particles has been systematically studied in Cu+Au collisions at $\sqrt{s_{_{NN}}}$ = 200 GeV for harmonics $n=$ 1-4 in the pseudorapidity range $|\eta|<1$. The directed flow in Cu+Au collisions is compared with the rapidity-odd and, for the first time, the rapidity-even components of charged particle directed flow in Au+Au collisions at $\sqrt{s_{_{NN}}}$ = 200~GeV. The slope of the directed flow pseudorapidity dependence in Cu+Au collisions is found to be similar to that in Au+Au collisions, with the intercept shifted toward positive $\eta$ values, i.e., the Cu-going direction. The mean transverse momentum projected onto the spectator plane, $\langle p_x\rangle$, in Cu+Au collision also exhibits approximately linear dependence on $\eta$ with the intercept at about $\eta\approx-0.4$, closer to the rapidity of the Cu+Au system center-of-mass. The observed dependencies find natural explanation in a picture of the directed flow originating partly due the "tilted source" and partly due to the rapidity dependent asymmetry in the initial density distribution. Charge-dependence of the $\langle p_x\rangle$ was also observed in Cu+Au collisions, indicating an effect of the initial electric field created by charge difference of the spectator protons in two colliding nuclei. The rapidity-even component of directed flow in Au+Au collisions is close to that in Pb+Pb collisions at $\sqrt{s_{_{NN}}}$ = 2.76 TeV, indicating a similar magnitude of dipole-like fluctuations in the initial-state density distribution. Higher harmonic flow in Cu+Au collisions exhibits similar trends to those observed in Au+Au and Pb+Pb collisions and is qualitatively reproduced by a viscous hydrodynamic model and a multi-phase transport model. For all harmonics with $n\ge2$ we observe an approximate scaling of $v_n$ with the number of constituent quarks.

Charge-Dependent Directed Flow in Cu+Au Collisions at sqrt[s_{NN}]=200 GeV.

We present the first measurement of charge-dependent directed flow in Cu+Au collisions at sqrt[s_{NN}]=200 GeV. The results are presented as a function of the particle transverse momentum and pseudorapidity for different centralities. A finite difference between the directed flow of positive and negative charged particles is observed that qualitatively agrees with the expectations from the effects of the initial strong electric field between two colliding ions with different nuclear charges. The measured difference in directed flow is much smaller than that obtained from the parton-hadron-string-dynamics model, which suggests that most of the electric charges, i.e., quarks and antiquarks, have not yet been created during the lifetime of the strong electric field, which is of the order of, or less than, 1 fm/c.

Charge-dependent anisotropic flow in Cu + Au collisions

We present the first measurements of charge-dependent directed flow in Cu+Au collisions at sNN=200 GeV. The directed flow has been measured as functions of the transverse momentum and pseudorapidity with the STAR detector. The results show a small but finite difference between positively and negatively charged particles. The difference is qualitatively explained by the patron-hadron-string-dynamics (PHSD) model including the effect of the electric field, but much smaller than the model calculation, which indicates only a small fraction of all final state quarks are created within the lifetime of the initial electric field. Higher-order azimuthal anisotropic flow is also presented up to the fourth-order for unidentified charged particles and up to the third-order for identified charged particles (π, K, and p). For unidentified particles, the results are reasonably described by the event-by-event viscous hydrodynamic model with η/s=0.08−0.16. The trends observed for identified particles in Cu+Au collisions are similar to those observed in symmetric (Au+Au) collisions.

PHENIX results on flow observables in asymmetric Cu + Au collisions

Measurements of anisotropic flow from Cu+Au sNN=200 GeV collisions in PHENIX at RHIC in 2012 are presented for inclusive charged particles and identified hadrons π±, K±, p, and p‾ at midrapidity. Fourier coefficients characterizing the azimuthal distribution of produced particles with respect to the event plane measured at forward rapidity are examined over a broad range of pT and collision centrality. Directed, elliptic, and triangular moments (v1, v2, v3 as functions of pT) all exhibit mass ordering. Comparisons are made to Cu+Cu and Au+Au systems as well as to hydrodynamical and transport model calculations [A. Adare, et al., “Measurements of directed, elliptic, and triangular flow in Cu+Au collisions at sNN=200 GeV”, arXiv:1509.07784.]. Unlike v2 and v3, v1 decreases with centrality, mass ordering is seen for all three, and v2 and v3 with respect to transverse momentum feature common scaling with 1/(εnNpart1/3).

Measurements of identified particle anisotropic flow in Cu + Au and U + U collisions by PHENIX experiment

In this paper, new measurements of anisotropic flow ( v 1 , v 2 ) for identified particles such as pions and protons in Cu + Au collisions at s N N = 200 GeV and U + U collisions at s N N = 193 GeV are reported. The anisotropic flow is studied as a function of p T and centrality in these two collision systems. In ultra-central U + U collisions (0–2% centrality), v 2 of protons shows a weak p T dependence for p T < 1.0 GeV/c . A positive v 1 for charged pions is observed for p T > 1 GeV/c with respect to the first-order event plane, the angle of which is determined by the Au-going spectators. The scaling of identified particle v 2 with the number of valence quarks ( n q ) has been observed in these two collision systems, with the transverse kinetic energy.

Elliptic flow and initial eccentricity in Cu+Cu and Au+Au collisions at RHIC

We present a systematic study of elliptic flow as a function of centrality, pseudorapidity, transverse momentum and energy for Cu+Cu and Au+Au collisions from the PHOBOS experiment. New data on elliptic flow in Cu+Cu collisions at are shown. Elliptic flow scaled by participant eccentricity is found to be similar for both systems when collisions with the same number of participants or the same average area density are compared. This similarity is observed over a wide range in pseudorapidity and transverse momentum, indicating that participant eccentricity is the relevant quantity for generating the azimuthal asymmetry leading to the observed elliptic flow.

Hadron-string cascade versus hydrodynamics in Cu+Cu collisions atsNN=200GeV

Single particle spectra as well as elliptic flow in Cu+Cu collisions at $\sqrt{{s}_{\mathit{NN}}}=200$ GeV are investigated within a hadronic cascade model and an ideal hydrodynamic model. Pseudorapidity distribution and transverse momentum spectra for charged hadrons are surprisingly comparable between these two models. However, a large deviation is predicted for the elliptic flow. The forthcoming experimental data will clarify the transport and thermalization aspects of matter produced in Cu+Cu collisions.

Superplastic Behavior and Activation Energies for Plastic Flow in Cu–Ag Mocrocomposites

No abstracts.

Characteristics of low temperature serrated flow in CuBe alloy

In the homogenized Cu2Be alloy discontinuous flow has been investigated at 4.2 K. The behaviour of serrated yielding is dependent on the strain rate and sample diameter. The strain rate sensitivity of the yield stress is slightly negative whereas the stress for the onset of serrated flow increases with increasing strain rate. The dependence of this stress as well as the yield stress on the sample diameter indicates that thermal instability plays an important role. In der homogenisierten Legierung Cu2Be wurde diskontinuierliches Fließen bei 4.2 K untersucht. Das Verhalten des diskontinuierlichen Fließen ist von der Verformungsgeschwindigkeit abhängig. Die Geschwindigkeitsempfindlichkeit der kritischen Fließspannung ist schwach negativ. Die Einsatz-spannung für diskontinuierliches Fließen steigt mit der Verformungsgeschwindigkeit. Beide charak-teristische Spannungen sind vom Probendurchmesser abhängig, was darauf schlißen läßt, daß eine thermische Instabilität eine wichtige Rolle spielt.

Study of the instability boundaries of plastic flow in Cu + 14 at.% Al single crystals at low temperatures

AbstractThe authors experimentally revealed the existence of the temperature‐strain rate region of jumplike deformation in Cu + 14 at.% Al single crystals between 4.2 and 25 K. For each particular temperature in this temperature range, there are a lower and an upper critical strain rates, between which deformation is jumplike. The character of transients occurring during strain rate variation was investigated by increasing the strain rate to the lower critical value. The experimental data are explained in terms of the thermomechanical instability concept and inertial effects of the sample‐machine system.

Onset of serrated flow in CuBe alloys

Onset of serrated flow in CuBe alloys