Examining the Necessity to Include Event-By-Event Fluctuations in Experimental Evaluations of Elliptical Flow

Andrade, Raquel Dully; Grassi, F.; Hama, Yogiro; Kodama, T.; Socolowski, O.

doi:10.1103/physrevlett.97.202302

Cited by 155 publications

(153 citation statements)

References 16 publications

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“…In very central collisions the ratio of conversion efficiencies for event-byevent vs. single-shot hydrodynamics is closer to 1, but it degrades strongly in very peripheral collisions where event-by-event evolution generates on average 30−40% less elliptic flow than single-shot hydrodynamics. The generic tendency of event-by-event hydrodynamic evolution of fluctuating initial profiles to generate less elliptic flow than expected from hydrodynamic evolution of the corresponding smooth average profile has been observed before [27,30]; our systematic study in Fig. 13a quantifies this effect over the full range of collision centralities.…”

Section: B Elliptic and Triangular Flowmentioning

confidence: 90%

“…In addition, widely held beliefs as to which moments of the initial eccentricity distribution are directly related to which moments of the final flow distribution [17,21,26] must be tested by generating the final states hydrodyamically event by event, i.e. separately for each fluctuating initial condition [20,[27][28][29][30][31]. These are the goals addressed in the present article.…”

Section: Introductionmentioning

confidence: 99%

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Event-by-event shape and flow fluctuations of relativistic heavy-ion collision fireballs

2011

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Heavy-ion collisions create deformed quark-gluon plasma (QGP) fireballs which explode anisotropically. The viscosity of the fireball matter determines its ability to convert the initial spatial deformation into momentum anisotropies that can be measured in the final hadron spectra. A quantitatively precise empirical extraction of the QGP viscosity thus requires a good understanding of the initial fireball deformation. This deformation fluctuates from event to event, and so does the finally observed momentum anisotropy. We present a harmonic decomposition of the initial fluctuations in shape and orientation of the fireball and perform event-by-event (2+1)-dimensional ideal fluid dynamical simulations to extract the resulting fluctuations in the magnitude and direction of the corresponding harmonic components of the final anisotropic flow at midrapidity. The final harmonic flow coefficients are found to depend non-linearly on the initial harmonic eccentricity coefficients. We show that, on average, initial density fluctuations suppress the buildup of elliptic flow relative to what one obtains from a smooth initial profile of the same eccentricity, and discuss implications for the phenomenological extraction of the QGP shear viscosity from experimental elliptic flow data.

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Section: B Elliptic and Triangular Flowmentioning

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Event-by-event shape and flow fluctuations of relativistic heavy-ion collision fireballs

2011

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“…Hydrodynamics with fluctuating IC reproduces the experimental charged particle elliptic flow even for the most central collisions at the Relativistic Heavy Ion Collider (RHIC) [1] which was underestimated by all earlier hydrodynamic calculations using smooth IC. E-by-E hydrodynamics also gives a better agreement of the experimental charged particle spectra towards higher p T by hardening the spectra [1,5], helps to understand the various structures observed in two-particle correlations [6] and is a necessary element in determining the shear viscosity (η/s) from simultaneous measurements of elliptic and triangular flow coefficients [7].…”

Section: Introductionmentioning

confidence: 99%

Elliptic flow of thermal photons from an event-by-event hydrodynamic model

et al. 2013

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Elliptic flow of direct photons in relativistic heavy ion collisions is believed to be dominated by contribution from thermal radiation of quark gluon plasma up to pT ∼ 5 GeV/c, although other sources start outshining the thermal contribution at already smaller values of pT in the direct photon spectrum. The elliptic flow of thermal photons from ideal hydrodynamics considering a smooth initial density distribution under-predicts the PHENIX direct photon data from 200A GeV Au+Au collisions at RHIC by a large margin in the range 1 < pT < 5 GeV/c. However, a significant enhancement of thermal photon production due to fluctuations in the initial QCD matter density distributions is expected. We show that such fluctuations result in substantially larger photon elliptic flow for pT > 2.5 GeV/c compared to a smooth initial-state-averaged density profile. The results from event-by-event hydrodynamics are found to be sensitive to the fluctuation size parameter. However, the effects of initial state fluctuations are insufficient to account for the discrepancy to the PHENIX data for direct photon elliptic flow. Furthermore, the photon v2 is reduced even more when we include the NLO pQCD prompt photon component. We also calculate the spectra and elliptic flow of thermal photons for 2.76A TeV Pb+Pb collisions at LHC and for the 0-40% centrality bin. Thermal photons from event-by-event hydrodynamics along with prompt photons from NLO pQCD calculations explain the ALICE preliminary direct photon data well in the region pT ≥ 2.5 GeV/c. Similar to RHIC, the elliptic flow results at LHC are again found to be much smaller than the ALICE preliminary v2 data.

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“…These fluctuations may be produced by inhomogeneous initial conditions which, as pointed out in [10], are the result of quantum fluctuations in the densities of the two colliding nuclei and also in the energy deposition mechanism. These fluctuations and their phenomenological implications have been studied extensively [11][12][13][14][15] because they may be responsible for the angular correlations of particle emission observed in heavy-ion experiments. There are also hydrodynamic fluctuations [10], which are the result of finite particle number effects in a given fluid cell.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear waves in second order conformal hydrodynamics

et al. 2015

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In this work we study wave propagation in dissipative relativistic fluids described by a simplified set of the 2nd order viscous conformal hydrodynamic equations corresponding to Israel-Stewart theory. Small amplitude waves are studied within the linearization approximation while waves with large amplitude are investigated using the reductive perturbation method, which is generalized to the case of 2nd order relativistic hydrodynamics. Our results indicate the presence of a "soliton-like" wave solution in Israel-Stewart hydrodynamics despite the presence of dissipation and relaxation effects.

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Examining the Necessity to Include Event-By-Event Fluctuations in Experimental Evaluations of Elliptical Flow

Cited by 155 publications

References 16 publications

Event-by-event shape and flow fluctuations of relativistic heavy-ion collision fireballs

Event-by-event shape and flow fluctuations of relativistic heavy-ion collision fireballs

Elliptic flow of thermal photons from an event-by-event hydrodynamic model

Nonlinear waves in second order conformal hydrodynamics

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