Initial conditions of QCD conserved charges in high energy nuclear collisions

In the hydrodynamical modeling of heavy-ion collisions it is necessary to
know the initial conditions for the full energy-momentum tensor and the
baryon, strange and electric (BSQ) conserved charges of Quantum
Chromodynamics (QCD). Different initial state models have been proposed to
determine the initial values of the energy-momentum tensor. However, little
is known for the initial conditions of the conserved charges BSQ. In this
talk, I will present a new procedure for dynamically generating conserved
charges BSQ to supplement an arbitrary initial condition for
ultrarelativistic heavy ion collisions. This algorithm, which we denote
ICCING (Initial Conserved Charges in Nuclear Geometries), treats an initial
distribution of energy density as if it were composed entirely of gluons. It
then samples the probabilities for a gluon to split into a quark-antiquark
pair, which we have calculated in the Color-Glass Condensate (CGC)
framework, to redistribute this energy density in space along with the
conserved charges carried only by quarks. In this way, we provide a new tool
to the community which can be incorporated into any framework to initialize
the QCD conserved charges. Interestingly, we find that the quark flavors
couple differently to the collision geometry: up and down quarks are
produced by the bulk event geometry, while strange and charm quarks are
preferentially produced from hot spots. As such, different quark flavors can
possess significantly different eccentricities which drive the ensuing
flavor-dependent flow response.

References:  1801.08986 [arxiv.org] ,  1808.04896 [arxiv.org] , 1911.10272
[arxiv.org] , 1911.12454 [arxiv.org]