Search results for "Elliptic Flow"
showing 10 items of 111 documents
Anisotropy of flow and the order of phase transition in relativistic heavy ion collisions
2005
Using a hydrodynamical model we study how the order of phase transition in the equation of state of strongly interacting matter affects single particle spectra, elliptic flow and higher order anisotropies in Au+Au collisions at RHIC (sqrt{s_NN}=200 GeV energy). We find that the single particle spectra are independent of the order of phase transition and that the fourth harmonic v_4(p_T) shows only a weak dependence in the p_T region where hydrodynamics is expected to work. The differential elliptic flow, v_2(p_T), of baryons shows the strongest dependence on equation of state. Surprisingly the closest fit to data was obtained when the equation of state had a strong first order phase transit…
Sensitivity of jet quenching to enhancement of the medium opacity near TC
2014
One of the main goals of the study of high transverse momentum (P_T) observables in the context of ultrarelativisic heavy-ion collisions is the determination of properties of the produced QCD matter. In particular, the transport coefficients qhat and ehat, characterizing the interaction of the medium with a high p_T parton, are accessible via high P_T probes. However, a precision extraction of their temperature dependence from current data faces the problem that neither the spacetime geometry of the evolving matter droplet nor the link between thermodynamics and transport coefficients is unambiguously known, and various conjectured scenarios how thermodynamics and transport coefficients beh…
Azimuthal anisotropy ofπ0andηmesons in Au + Au collisions atsNN=200GeV
2013
The azimuthal anisotropy coefficients v2 and v4 of p 0 and. mesons are measured in Au + Au collisions at root s(NN) = 200 GeV as a function of transverse momentum p(T) (1-14 GeV/c) and centrality. The extracted v(2) coefficients are found to be consistent between the two meson species over the measured p(T) range. The ratio of v(4)/v(2)(2) for pi(0) mesons is found to be independent of p(T) for 1- 9 GeV/c, implying a lack of sensitivity of the ratio to the change of underlying physics with p(T). Furthermore, the ratio of v(4)/v(2)(2) is systematically larger in central collisions, which may reflect the combined effects of fluctuations in the initial collision geometry and finite viscosity i…
Influence of initial state fluctuations on the production of thermal photons
2012
Inhomogeneities in the initial QCD matter density distribution increase the production of thermal photons significantly compared to a smooth initial-state-averaged profile in the region $p_T > 1$ GeV/$c$ in an ideal hydrodynamic calculation. This relative enhancement is more pronounced for peripheral collisions, for smaller size systems as well as for lower beam energies. A suitably normalized ratio of central-to-peripheral yield of thermal photons reduce the uncertainties in the hydrodynamical initial conditions and can be a useful parameter to study the density fluctuations and their size. The fluctuations in the initial density distribution also lead to a larger elliptic flow of therm…
Event-by-event hydrodynamics and elliptic flow from fluctuating initial states
2010
We develop a framework for event-by-event ideal hydrodynamics to study the differential elliptic flow which is measured at different centralities in Au+Au collisions at Relativistic Heavy Ion Collider (RHIC). Fluctuating initial energy density profiles, which here are the event-by-event analogues of the eWN profiles, are created using a Monte Carlo Glauber model. Using the same event plane method for obtaining $v_2$ as in the data analysis, we can reproduce both the measured centrality dependence and the $p_T$ shape of charged-particle elliptic flow up to $p_T\sim2$~GeV. We also consider the relation of elliptic flow to the initial state eccentricity using different reference planes, and di…
Elliptic and Hexadecapole Flow of Charged Hadrons inAu+AuCollisions atsNN=200 GeV
2010
Differential measurements of the elliptic (upsilon(2)) and hexadecapole (upsilon(4)) Fourier flow coefficients are reported for charged hadrons as a function of transverse momentum (p(T)) and collision centrality or number of participant nucleons (N-part) for Au + Au collisions at root s(NN) = 200 GeV/ The upsilon(2,4) measurements at pseudorapidity vertical bar eta vertical bar <= 0.35, obtained with four separate reaction-plane detectors positioned in the range 1.0 < vertical bar eta vertical bar < 3.9, show good agreement, indicating the absence of significant Delta eta-dependent nonflow correlations. Sizable values for upsilon(4)(p(T)) are observed with a ratio upsilon(4)(p(T), N-part)/…
Observation of Long-Range Elliptic Azimuthal Anisotropies ins=13and 2.76 TeVppCollisions with the ATLAS Detector
2016
ATLAS has measured two-particle correlations as a function of relative azimuthal-angle, $\Delta \phi$, and pseudorapidity, $\Delta \eta$, in $\sqrt{s}$=13 and 2.76 TeV $pp$ collisions at the LHC using charged particles measured in the pseudorapidity interval $|\eta|$<2.5. The correlation functions evaluated in different intervals of measured charged-particle multiplicity show a multiplicity-dependent enhancement at $\Delta \phi \sim 0$ that extends over a wide range of $\Delta\eta$, which has been referred to as the "ridge". Per-trigger-particle yields, $Y(\Delta \phi)$, are measured over 2<$|\Delta\eta|$<5. For both collision energies, the $Y(\Delta \phi)$ distribution in all multiplicity …
Dissipation and Elliptic Flow at Relativistic Energies
2004
We compare elliptic flow evolution from ideal hydrodynamics and covariant parton transport theory, and show that, for conditions expected at RHIC, dissipation significantly reduces elliptic flow even for extreme parton cross sections and/or densities ${\ensuremath{\sigma}}_{gg}\ifmmode\times\else\texttimes\fi{}dN/d\ensuremath{\eta}(b=0)\ensuremath{\sim}45\text{ }\mathrm{m}\mathrm{b}\ifmmode\times\else\texttimes\fi{}1000$. The difference between transport and hydrodynamic elliptic flow is established rather early during the evolution of the system, but the buildup of elliptic flow is insensitive to the choice of the initial (formation or thermalization) time in both models.
J/ψElliptic Flow in Pb-Pb Collisions atsNN=2.76 TeV
2013
We report on the first measurement of inclusive J/psi elliptic flow v(2) in heavy-ion collisions at the LHC. The measurement is performed with the ALICE detector in Pb-Pb collisions at root s(NN) = 2.76 TeV in the rapidity range 2.5 < y < 4.0. The dependence of the J/psi v(2) on the collision centrality and on the J/psi transverse momentum is studied in the range 0 <= p(T) < 10 GeV/c. For semicentral Pb-Pb collisions at root s(NN) = 2.76 TeV, an indication of nonzero v(2) is observed with a largest measured value of v(2) = 0.116 +/-0.046(stat) +/- 0.029(syst) for J/psi in the transverse momentum range 2 <= p(T) < 4 GeV/c. The elliptic flow measurement complements the previously reported ALI…
Quadrupole Anisotropy in Dihadron Azimuthal Correlations in Centrald+AuCollisions atsNN=200 GeV
2013
The PHENIX collaboration at the Relativistic Heavy Ion Collider (RHIC) reports measurements of azimuthal dihadron correlations near midrapidity in d + Au collisions at root s(NN) = 200 GeV. These measurements complement recent analyses by experiments at the Large Hadron Collider (LHC) involving central p + Pb collisions at root s(NN) = 5.02 TeV, which have indicated strong anisotropic long-range correlations in angular distributions of hadron pairs. The origin of these anisotropies is currently unknown. Various competing explanations include parton saturation and hydrodynamic flow. We observe qualitatively similar, but larger, anisotropies in d + Au collisions at RHIC compared to those seen…