Measuring shear viscosity using correlations

Gavin, Sean; Abdelaziz, Mohamed

doi:10.1590/s0103-97332007000600020

Cited by 6 publications

(9 citation statements)

References 19 publications

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“…It is therefore very reassuring when actual empirical evidence in support of the supposed phase diagram accrues, particularly the crossover at small baryon density, as for example the scaling of moments of the distribution for baryon-number fluctuations with volume (or as proxy, number of participants) [10,11]. And we have relatively solid evidence that the ratio of viscosity to entropy density is low [12,13] and not too far above the renowned 1/(4π) bound [14].…”

Section: Introductionmentioning

confidence: 57%

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Angular power spectrum in publically released ALICE events

Llanes-Estrada

Martinez

2018

Nuclear Physics A

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Section: Introductionmentioning

confidence: 57%

“…This number, with a large uncertainty, is not huge, though other extractions of this quantity also based on statistical methods [13] yield results about a factor 10 smaller. Of course we do not take the result of Eq.…”

Section: A Possible Extraction Of η/Smentioning

confidence: 92%

Angular power spectrum in publically released ALICE events

Llanes-Estrada

Martinez

2018

Nuclear Physics A

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“…Additionally, one can also use the measureC, defined in Sect. 2, to study the transverse momentum correlations [3,11,12]. We argue that a differential version of all the observables, as defined in the previous section, may provide an equivalent or even better way to estimate the medium viscosity.…”

Section: Transverse Momentum Differential Correlationsmentioning

confidence: 90%

“…Extensions of fluctuation variables Φ pt [9] and σ pt [10] are also possible. In this work, we study three differential observables namely, inclusive and event-wise correlation functions and a differential version of the measureC, used by Gavin [11,12] to estimate the viscosity per unit entropy of the matter formed in A + A collisions. The observable definitions and notation used in this work are presented in Sect.…”

Section: Introductionmentioning

confidence: 99%

Methods for the study of transverse momentum differential correlations

Sharma

Pruneau

2009

Phys. Rev. C

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We introduce and compare three differential correlation functions for the study of transverse momentum correlation in p + p and A + A collisions. These consist of inclusive, event-wise and a differential version of the correlation measureC introduced by Gavin [1] for experimental study of the viscosity per unit entropy of the matter produced in A + A collisions. We study the quantitative difference between the three observables on the basis of PYTHIA simulations of p + p collisions and A+A collisions consisting of an arbitrary superposition of p+p collision events at √ s =200 GeV. We observe that inclusive and event-wise correlation functions are remarkably identical to each other where as the observableC differs from the two. We study the robustness and efficiency dependencies of these observables based on truncated Taylor expansions in efficiency in p + p collisions and on the basis of Monte Carlo simulation using an adhoc detector efficiency parameterization. We find that all the three observables are essentially independent of detector efficiency. We additionally study the scaling of the correlation measures and find all the observables exhibit an approximate 1/N dependence of the number of participants (N) in A + A collisions. Finally, we study the impact of flow-like anisotropy on the inclusive correlation function and find flow imparts azimuthal modulations similar to those observed with two-particle densities.

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“…It was shown in [12][13][14] that transverse momentum diffuses longitudinally with the viscosity playing a role in determining the diffusion constant. Restating the arguments, one can consider a boost-invariant system with a momentum per rapidity slice, P x (η) or P y (η), where…”

Section: Momentum Diffusion and Viscositymentioning

confidence: 99%

Effects of momentum conservation and flow on angular correlations observed in experiments at the BNL Relativistic Heavy Ion Collider

2011

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Correlations of azimuthal angles observed at RHIC have gained great attention due to the prospect of identifying fluctuations of parity-odd regions in the field sector of QCD. Whereas the observable of interest related to parity fluctuations involves subtracting opposite-sign from same-sign correlations, the STAR collaboration reported the same-sign and opposite-sign correlations separately. It is shown here how momentum conservation combined with collective elliptic flow contributes significantly to this class of correlations, though not to the difference between the opposite-and same-sign observables. The effects are modeled with a crude simulation of a pion gas. Though the simulation reproduces the scale of the correlation, the centrality dependence is found to be sufficiently different in character to suggest additional considerations beyond those present in the pion gas simulation presented here.

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Measuring shear viscosity using correlations

Abstract: Measurements of transverse momentum fluctuations can be used to determine the shear viscosity [1]. We use current data to estimate the viscosity-to-entropy ratio in the range from 0.08 to 0.3, and discuss how future measurements can reduce this uncertainty.

Cited by 6 publications

References 19 publications

Angular power spectrum in publically released ALICE events

Angular power spectrum in publically released ALICE events

Methods for the study of transverse momentum differential correlations

Effects of momentum conservation and flow on angular correlations observed in experiments at the BNL Relativistic Heavy Ion Collider

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