A data-driven approach to quantifying the Hot and Dense QCD Matter shear viscosity of nature’s most ideal liquid Unraveling the Mysteries of the Strongly Interacting Quark-Gluon-Plasma Steffen A. Bass A Community White Paper on the Future of Relativistic Heavy-Ion Physics in the US http://www.facebook.com/DukeQCD @Steffen_Bass
Introduction: • Phase diagram of matter • Quark-Gluon-Plasma
Quarks & Gluons: Elementary Building-Blocks of Matter Molecule Atom Nucleus Proton/Neutron Quark Elementary Particles: • 12 elementary building blocks of nature (plus anti-particles) • only need three for creation of ordinary matter (u, d, e) • strong force mediates the interaction between quarks via exchange of gluons
Phases of Matter gaseous by adding/removing heat, phase of matter can be changed between solid, liquid and gaseous Pressure plays an important role for the value of the transition liquid temperature between the phases boiling temperature: • sea level: 100 ℃ solid • Mt. Everest: 71 ℃
Phase Diagram Ordinary Matter: • phases determined by (electro- magnetic) interaction • apply heat & pressure to study phase-diagram 5
Phase Diagram Phases of QCD matter: Ordinary Matter: • heat & compress QCD matter: • phases determined by (electro- ‣ collide heavy atomic nuclei magnetic) interaction • numerical simulations: • apply heat & pressure to study phase-diagram ‣ solve partition function (Lattice) 5
QGP and the Early Universe • a few microseconds after the Big Bang the entire Universe was in a QGP state • compressing & heating nuclear matter allows to investigate the history of the Universe • the only means of recreating temperatures and densities of the early Universe is by colliding beams of ultra-relativistic heavy- ions
Telescopes for the Early Universe: Heavy-Ion Collider Facilities
Heating & Compressing QCD Matter The only way to heat & compress QCD matter under controlled laboratory conditions is by colliding two heavy atomic nuclei!
Heating & Compressing QCD Matter The only way to heat & compress QCD matter under controlled ALICE experiment @ CERN: laboratory conditions is by colliding two heavy atomic nuclei! • 1000+ scientists from 105+ institutions • dimensions: 26m long, 16m high, 16m wide • weight: 10,000 tons two more experiments w/ Heavy-Ions: • CMS, ATLAS
Heating & Compressing QCD Matter The only way to heat & compress QCD matter under controlled ALICE experiment @ CERN: typical Pb+Pb collision @ LHC: laboratory conditions is by colliding two heavy atomic nuclei! typical Pb+Pb collision @ LHC: • 1000s of tracks • 1000+ scientists from 105+ institutions • task: reconstruction of final state to • dimensions: 26m long, 16m high, 16m wide characterize matter created in collision • weight: 10,000 tons two more experiments w/ Heavy-Ions: • CMS, ATLAS
RHIC: A dedicated QGP Machine Brookhaven National Laboratory: Relativistic Heavy-Ion Collider
RHIC: A dedicated QGP Machine Brookhaven National Laboratory: Relativistic Heavy-Ion Collider • 2 large experiments (STAR, PHENIX) • 2 small experiments (PHOBOS, BRAHMS)
RHIC: A dedicated QGP Machine Brookhaven National Laboratory: Relativistic Heavy-Ion Collider • 2 large experiments (STAR, PHENIX) • typical collision @ RHIC: 1000s of tracks • 2 small experiments (PHOBOS, • task: reconstruction of final state to BRAHMS) characterize matter created in collision
Transport Theory: Connecting Data to Knowledge
Computational Modeling 3+1D Hydro + Boltzmann Hybrid
Computational Modeling 3+1D Hydro + Boltzmann Hybrid
Time-Evolution of a Heavy-Ion Collision
Time-Evolution of a Heavy-Ion Collision 10 x 10 -23 s 30 x 10 -23 s 1x 10 -23 s
Time-Evolution of a Heavy-Ion Collision nuclei at 99.99% speed of light 10 x 10 -23 s 30 x 10 -23 s 1x 10 -23 s
Time-Evolution of a Heavy-Ion Collision nuclei at 99.99% Quark-Gluon-Plasma speed of light 10 x 10 -23 s 30 x 10 -23 s 1x 10 -23 s
Time-Evolution of a Heavy-Ion Collision nuclei at 99.99% hadronic final state Quark-Gluon-Plasma speed of light interactions 10 x 10 -23 s 30 x 10 -23 s 1x 10 -23 s
Time-Evolution of a Heavy-Ion Collision measurable (stable) nuclei at 99.99% hadronic final state Quark-Gluon-Plasma particles in detector speed of light interactions 10 x 10 -23 s 30 x 10 -23 s 1x 10 -23 s
Time-Evolution of a Heavy-Ion Collision measurable (stable) nuclei at 99.99% hadronic final state Quark-Gluon-Plasma particles in detector speed of light interactions 10 x 10 -23 s 30 x 10 -23 s 1x 10 -23 s non-equilibrium viscous fluid early time hadronic transport dynamics dynamics Principal Challenges of Probing the QGP with Heavy-Ion Collisions: • time-scale of the collision process: 10 -24 seconds! [too short to resolve] • characteristic length scale: 10 -15 meters! [too small to resolve] • confinement: quarks & gluons form bound states, experiments don’t observe them directly ‣ computational models are need to connect the experiments to QGP properties!
Transport Theory microscopic transport models based (viscous) relativistic fluid dynamics: on the Boltzmann Equation : • transport of macroscopic degrees of freedom • transport of a system of microscopic particles • based on conservation laws: • all interactions are based on binary scattering � � � � t + � E × � p � f 1 ( � r, t ) = C ( � r, t ) p, � p, � �� r = ε u i u k + P ( δ ik + u i u k ) T ik processes � � i u k + � k u i � 2 � η 3 δ ik � · u � diffusive transport models based on the Langevin Equation : + ς δ ik � · u • transport of a system of microscopic particles in (plus an additional 9 eqns. for dissipative flows) a thermal medium • interactions contain a drag term related to the properties of the medium and a noise term hybrid transport models: representing random collisions • combine microscopic & macroscopic degrees p ( t ) − � of freedom v · ∆ t + � p ( t + ∆ t ) = � � ( t ) ∆ t � 2 T � • current state of the art for RHIC modeling
Transport Theory microscopic transport models based (viscous) relativistic fluid dynamics: on the Boltzmann Equation : • transport of macroscopic degrees of freedom • transport of a system of microscopic particles • based on conservation laws: • all interactions are based on binary scattering � � � � t + � E × � p � f 1 ( � r, t ) = C ( � r, t ) p, � p, � �� r = ε u i u k + P ( δ ik + u i u k ) T ik processes � � i u k + � k u i � 2 � η 3 δ ik � · u � diffusive transport models based on the Langevin Equation : + ς δ ik � · u • transport of a system of microscopic particles in (plus an additional 9 eqns. for dissipative flows) a thermal medium • interactions contain a drag term related to the properties of the medium and a noise term hybrid transport models: representing random collisions • combine microscopic & macroscopic degrees p ( t ) − � of freedom v · ∆ t + � p ( t + ∆ t ) = � � ( t ) ∆ t � 2 T � • current state of the art for RHIC modeling Each transport model relies on roughly a dozen physics parameters to describe the time-evolution of the collision and its final state. These physics parameters act as a representation of the information we wish to extract from RHIC & LHC.
Collision Geometry: Elliptic Flow • two nuclei collide rarely head-on, but mostly with an offset: z Reaction plane only matter in the overlap area gets compressed and heated up y x
Collision Geometry: Elliptic Flow • two nuclei collide rarely head-on, but mostly with an offset: z Reaction plane only matter in the overlap area gets compressed and heated up y x elliptic flow (v 2 ): • gradients of almond-shape surface will lead to preferential emission in the reaction plane • asymmetry out- vs. in-plane emission is quantified by 2 nd Fourier coefficient of angular distribution: v 2 Ø vRFD: good agreement with data for very small η /s
How to determine the the shear viscosity of the QGP?
Determining the QGP Shear Viscosity via a Model to Data Comparison Model Parameter: experimental data: eqn. of state π /K/P spectra shear viscosity yields vs. centrality & beam initial state elliptic flow pre-equilibrium dynamics HBT thermalization time charge correlations & BFs quark/hadron chemistry density correlations particlization/freeze-out
Determining the QGP Shear Viscosity via a Model to Data Comparison Model Parameter: experimental data: eqn. of state π /K/P spectra shear viscosity yields vs. centrality & beam initial state elliptic flow pre-equilibrium dynamics HBT thermalization time charge correlations & BFs quark/hadron chemistry density correlations particlization/freeze-out
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