Encoding spatial–momentum correlations in the early-time energy-momentum tensor, a simple case

by Óscar García Montero (University of Santiago de Compostela)

Monday Jun 15, 2026, 4:15 PM → 5:45 PM Europe/Berlin

D6-135 (UHG)

Saturation-based  models for the initial state of heavy-ion collisions typically use the assumption of isotropy, hence ignoring the correlations between gluon momenta within the nucleus and the later spatial color charge profile. In this way, the GBW model provides a simple and widely-used parametrization of the dipole amplitude, but in its standard form it is local and isotropic. In this work I derive an extension of the GBW dipole which encodes spatial–momentum correlations arising from the geometry of the colliding system. Starting from the Gaussian (MV) CGC effective action, I perform a gradient expansion of the color charge density. I will discuss how the positive-definiteness of this new kernel gives rise to useful validity conditions, relevant for phenomenology, and obtain the corresponding unintegrated gluon distribution. Using the kt-factorization limit of the CGC framework, I compute the energy-momentum tensor, and show how spatial gradients seed a momentum anisotropy $\epsilon_p$, offering analytic intuition for the 3+1D structure of the initial state in heavy-ion collisions.

2026-06-15_GarciaMontero_Oscar.pdf