We present an analytical calculation of the covariance of the energy-momentum tensor associated to the gluon field produced in ultra-relativistic heavy ion collisions at early times, the Glasma. This object involves the two-point and single-point correlators of the energy-momentum tensor (〈Tμν (x⊥)Tσρ(y⊥)〉 and 〈Tμν (x⊥)〉, respectively) at proper time τ = 0+. Our approach is based on the Color Glass Condensate effective theory, which allows us to map the fluctuations of the valence color sources in the colliding nuclei to those of the energy-momentum tensor of the produced gluon fields via the solution of the classical equations of motion in the presence of external currents. The color sources in the two colliding nuclei are characterized by Gaussian correlations, albeit in more generality than in the McLerran-Venugopalan model, allowing for non-trivial impact parameter and transverse dependence of the two-point correlator. We compare our results to those obtained under the Glasma Graph approximation, finding agreement in the limit of short transverse separations. However, important differences arise at larger transverse separations, where our result displays a slower fall-off than the Glasma Graph result (1/r2 vs. 1/r4 power-law decay), indicating that the color screening of the correlations in the transverse plane occurs at distances larger than 1/Qs by a logarithmic factor sensitive to the infrared. In the Glasma flux tube picture, this implies that the color domains are larger than originally estimated.
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M. Luzum and H. Petersen, Initial State Fluctuations and Final State Correlations in Relativistic Heavy-Ion Collisions, J. Phys.G 41 (2014) 063102 [arXiv:1312.5503] [INSPIRE].
F. Gelis, Initial state and thermalization in the Color Glass Condensate framework, Int. J. Mod. Phys.E 24 (2015) 1530008 [arXiv:1508.07974] [INSPIRE].
A. Kurkela, A. Mazeliauskas, J.-F. Paquet, S. Schlichting and D. Teaney, Matching the non-equilibrium initial stage of heavy ion collisions to hydrodynamics with QCD kinetic theory, arXiv:1805.01604 [INSPIRE].
A. Accardi et al., Electron Ion Collider: The Next QCD Frontier, Eur. Phys. J.A 52 (2016) 268 [arXiv:1212.1701] [INSPIRE].
L.D. McLerran and R. Venugopalan, Computing quark and gluon distribution functions for very large nuclei, Phys. Rev.D 49 (1994) 2233 [hep-ph/9309289] [INSPIRE].
T. Lappi and S. Schlichting, Linearly polarized gluons and axial charge fluctuations in the Glasma, Phys. Rev.D 97 (2018) 034034 [arXiv:1708.08625] [INSPIRE].
J.-P. Blaizot, W. Broniowski and J.-Y. Ollitrault, Correlations in the Monte Carlo Glauber model, Phys. Rev.C 90 (2014) 034906 [arXiv:1405.3274] [INSPIRE].
J.-P. Blaizot, W. Broniowski and J.-Y. Ollitrault, Continuous description of fluctuating eccentricities, Phys. Lett.B 738 (2014) 166 [arXiv:1405.3572] [INSPIRE].
B. Schenke, P. Tribedy and R. Venugopalan, Event-by-event gluon multiplicity, energy density and eccentricities in ultrarelativistic heavy-ion collisions, Phys. Rev.C 86 (2012) 034908 [arXiv:1206.6805] [INSPIRE].
J.E. Bernhard, J.S. Moreland, S.A. Bass, J. Liu and U. Heinz, Applying Bayesian parameter estimation to relativistic heavy-ion collisions: simultaneous characterization of the initial state and quark-gluon plasma medium, Phys. Rev.C 94 (2016) 024907 [arXiv:1605.03954] [INSPIRE].
S. Floerchinger and U.A. Wiedemann, Characterization of initial fluctuations for the hydrodynamical description of heavy ion collisions, Phys. Rev.C 88 (2013) 044906 [arXiv:1307.7611] [INSPIRE].
S. Floerchinger and U.A. Wiedemann, Mode-by-mode fluid dynamics for relativistic heavy ion collisions, Phys. Lett.B 728 (2014) 407 [arXiv:1307.3453] [INSPIRE].
A. Kovner, L.D. McLerran and H. Weigert, Gluon production at high transverse momentum in the McLerran-Venugopalan model of nuclear structure functions, Phys. Rev.D 52 (1995) 3809 [hep-ph/9505320] [INSPIRE].
G. Chen, R.J. Fries, J.I. Kapusta and Y. Li, Early Time Dynamics of Gluon Fields in High Energy Nuclear Collisions, Phys. Rev.C 92 (2015) 064912 [arXiv:1507.03524] [INSPIRE].
H. Fujii, F. Gelis and R. Venugopalan, Quark pair production in high energy pA collisions: General features, Nucl. Phys.A 780 (2006) 146 [hep-ph/0603099] [INSPIRE].
C. Marquet, Forward inclusive dijet production and azimuthal correlations in p(A) collisions, Nucl. Phys.A 796 (2007) 41 [arXiv:0708.0231] [INSPIRE].
Y.V. Kovchegov, J. Kuokkanen, K. Rummukainen and H. Weigert, Subleading-N(c) corrections in non-linear small-x evolution, Nucl. Phys.A 823 (2009) 47 [arXiv:0812.3238] [INSPIRE].
C. Marquet and H. Weigert, New observables to test the Color Glass Condensate beyond the large-Nclimit, Nucl. Phys.A 843 (2010) 68 [arXiv:1003.0813] [INSPIRE].
J.P. Blaizot, F. Gelis and R. Venugopalan, High-energy pA collisions in the color glass condensate approach. 1. Gluon production and the Cronin effect, Nucl. Phys.A 743 (2004) 13 [hep-ph/0402256] [INSPIRE].
A. Kovner, L.D. McLerran and H. Weigert, Gluon production from nonAbelian Weizsacker-Williams fields in nucleus-nucleus collisions, Phys. Rev.D 52 (1995) 6231 [hep-ph/9502289] [INSPIRE].
R.J. Fries, J.I. Kapusta and Y. Li, Near-fields and initial energy density in the color glass condensate model, nucl-th/0604054 [INSPIRE].
F. Fillion-Gourdeau and S. Jeon, Wilson lines: Color charge densities correlators and the production of eta-prime in the CGC for pp and pA collisions, Phys. Rev.C 79 (2009) 025204 [arXiv:0808.2154] [INSPIRE].