Ekaterina Retinskaya, Matthew Luzum, Jean-Yves Ollitrault
Published 2012-03-05, updated 2013-04-30Version 4
We analyze published data from the ALICE Collaboration in order to obtain the first extraction of the recently-proposed rapidity-even directed flow observable v1. An accounting of the correlation due to the conservation of transverse momentum restores the factorization seen by ALICE in all other Fourier harmonics and thus indicates that the remaining correlation gives a reliable measurement of directed flow. We then carry out the first viscous hydrodynamic calculation of directed flow, and show that it is less sensitive to viscosity than higher harmonics. This allows for a direct extraction of the dipole asymmetry of the initial state, providing a strict constraint on the non-equilibrium dynamics of the early-time system. A prediction is then made for v1 in Au-Au collisions at RHIC.
Comments: v4: Replaced Fig.4. Hydro calculation was supposed to use parameters from Ref.[32], but had the wrong initial temperature. Text unchanged. v3:Added data files. v2: Several values in Table 1 corrected and estimate of systematic error added (Table 1 and Fig.2). Mistake corrected in the Phobos Monte-Carlo Glauber calculation (Fig.3). Same as published version except for fixed typos in Table I
Journal: Phys.Rev.Lett.108:252302,2012
Three-Particle Correlations from Parton Cascades in Au+Au Collisions
Elliptic flow in 200 A GeV Au+Au collisions and 2.76 A TeV Pb+Pb collisions: insights from viscous hydrodynamics + hadron cascade hybrid model
Suppression of high $p_T$ hadron spectra in $p+A$ collisions
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