Heavy ion collisions reproduce droplets of the
trillions-of-degrees-hot liquid that filled the microseconds-old
universe, called quark-gluon plasma (QGP). Over the past twenty years,
data obtained via recreating this primordial fluid have shown that it
is the most liquid liquid in the universe, making it the first complex
matter to form as well as the source of all protons and neutrons.
After a look at what we have learned about the formation and
properties of this original liquid from heavy ion collisions, I will
focus on the road ahead. I will frame questions that motivate
experimental measurements coming soon, including: How does liquid QGP
change as it is doped with an excess of quarks over antiquarks? Is
there a critical point in the region of the QCD phase diagram as a
function of temperature and doping that heavy ion collisions can
explore? How does a strongly coupled liquid emerge, given that what
you will see if you can probe QGP with high resolution is weakly
coupled quarks and gluons? How can we use jets to see the inner
workings of QGP and answer this question?
I. Giardina, G. Cavoto